I have a lifted LX470 with 35 inch rims and Terrain Tamer shocks. The ride is really good. I put in new Terrain Tamer shocks 6 months ago but last week both front shock were completely dead and were replaced by the dealer under warranty. No idea why this happened. I did not drive offroad at all, just tarmac. Just bad batch? Is it because of the lift? No idea. Hope they last now longer....
LX570 AHC height modifications (lift it!) (2 Viewers)
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1world1love
SILVER Star
Teckis is spot on with his explanation. I would further add that if you are running stock and otherwise not maxing out your payload on a regular basis, you are probably fine and not likely to experience any issues by doing the sensor lift.
If you are concerned, the easiest option is to add spring spacers. Even the OEM spacers would work fine.
The rationale for installing the uprated 100 series AHC springs was to compensate for all of the permanent mods and excessive payload. To be clear, the springs that I used were designed for AHC and while they are certainly stiffer than the stock springs, they are nowhere close to standard, non-AHC springs which are much stiffer.
I took (what I thought was) a gamble on a front-only AHC sensor lift. The front two sensors were mounted in totally different positions, not centered, so I was worried bottoming them out would add a weird tilt.
I was actually surprised it worked perfectly. In neutral driver's is measuring 91cm, rear drivers 91cm. Front passenger 91.5cm, rear passenger 91.5cm. There was already a driver's side tilt of about .5 cm before the sensor lift. So basically I got the effect of adding a 1" front spacer.
I was actually surprised it worked perfectly. In neutral driver's is measuring 91cm, rear drivers 91cm. Front passenger 91.5cm, rear passenger 91.5cm. There was already a driver's side tilt of about .5 cm before the sensor lift. So basically I got the effect of adding a 1" front spacer.
Can anyone help comments on the leveling after the sensor lift ? I have a roof top tent installed and found the AHC seems can get the vehicle properly leveled when camping, but at a flat parking lot the roof seems not leveled with the rake looking on vehicle. Sorry I still haven't figure out a good method to measure accurately at this time.
Since the sensor lift will make the height more identical front vs back, I suppose the roof should be more leveled when parked ? How will it impact on the AHC auto-leveling when parked ?
Regarding the leveling, this might be silly but do we have some sort of leveling monitoring system built in ? I have a hard time to figure out if my RTT is leveled... I am usually using phone app and put my phone on top of center dash , and don't seem to find a better flat spot.
Since the sensor lift will make the height more identical front vs back, I suppose the roof should be more leveled when parked ? How will it impact on the AHC auto-leveling when parked ?
Regarding the leveling, this might be silly but do we have some sort of leveling monitoring system built in ? I have a hard time to figure out if my RTT is leveled... I am usually using phone app and put my phone on top of center dash , and don't seem to find a better flat spot.
A sensor lift can help with front to back rake. I don't think modifying sensors can help with right to left leveling, at least not consistently since at times each axle shares pressure between the left and right sides.
I don't know of any specific parked auto leveling, so not sure what you are referring to here.
I think some people attach a bubble level (or 2 ) to their RTT.
I don't know of any specific parked auto leveling, so not sure what you are referring to here.
I think some people attach a bubble level (or 2 ) to their RTT.
Yep. I use these and have pieces of 2x4 if needed to level it out.
Hopkins 03926 Never Fade Two Way Stick-on Level Amazon product ASIN B00EO4PZIA
Most vehicles have some rake built into the suspension including the LX. For reasons including load on rear (though AHC doesn't care as it's constant height), and probably due to NHTSA standards for crash bar heights and such. Fortunately, with AHC, we can level our suspension to remove some rake without impacting load handling. I have mine sensor lifted 1" front .75" rear to help rake a tad.
The best thing IMO to help with car camping or RTT leveling is adding airbags to the rear suspension. I usually slam AHC in low when parking to help ingress/egress with RTT height, and maximize suspension stroke to aid leveling. I make sure I'm a tad nose up parked. Then use rear airbags to level front to back, and side to side. Works like magic with no need to stack rocks/levelers/repeat until level which can be frustrating at times. Seriously, best thing ever for leveling. But it also works great for expanding AHC load capacity beyond 2000lbs payload, and perhaps as backup in the rare situation if I were to ever have AHC issues.
Adding Airbags to AHC
Picture is probably too subtle to show but it's part of the why - adding airbags creates the ability to level the vehicle side to side and front to back for backcountry car camping. In the pic, I have the right side jacked up 2" with about 25 PSI in the right rear bag. Secondly, while AHC has...
forum.ih8mud.com
The stick-on level is a great idea to put on my RTT for leveling. I usually eye ball it and its hard to do when in dark. I am currently using traction boards when AHC cannot adjust it for me, thinking maybe give the level blocks a try as seems more convenient to pack and storage in trunk.
I mean AHC will auto level the vehicle when fully stopped in a few seconds, no matter P or D gear. Should be the same while moving but just hard to notice. I never paid much attention until installed RTT , it is so satisfying to see all 4 wheels are in different level due to uneven surface but the RTT is leveled perfectly.
I guess I would need to figure out if the roof is leveled with vs w/out rake first. I will be very happy to do a sensor lift if even helps RTT leveling.Most vehicles have some rake built into the suspension including the LX. For reasons including load on rear (though AHC doesn't care as it's constant height), and probably due to NHTSA standards for crash bar heights and such. Fortunately, with AHC, we can level our suspension to remove some rake without impacting load handling. I have mine sensor lifted 1" front .75" rear to help rake a tad.
The best thing IMO to help with car camping or RTT leveling is adding airbags to the rear suspension. I usually slam AHC in low when parking to help ingress/egress with RTT height, and maximize suspension stroke to aid leveling. I make sure I'm a tad nose up parked. Then use rear airbags to level front to back, and side to side. Works like magic with no need to stack rocks/levelers/repeat until level which can be frustrating at times. Seriously, best thing ever for leveling. But it also works great for expanding AHC load capacity beyond 2000lbs payload, and perhaps as backup in the rare situation if I were to ever have AHC issues.
Adding Airbags to AHC
Picture is probably too subtle to show but it's part of the why - adding airbags creates the ability to level the vehicle side to side and front to back for backcountry car camping. In the pic, I have the right side jacked up 2" with about 25 PSI in the right rear bag. Secondly, while AHC has...
The airbag method is brilliant. I would definitely consider it if towing a lot. How much the airbag can help on adjust the suspension stoke , basically the range from low to high mode (or maybe even more)?
Pretty large stroke, and easily more than just AHC low to high.
Added a more specific thread to airbag leveling here
Leveling rig for Car Camping / RTT
This was brought up in another thread and thought there's enough to discuss that it deserves its own - Many of us car camp or use Roof Top Tents and I think many would agree it's worth the time and effort to have a level rig to sleep in. Some have had the pleasure of playing the rock leveling...
forum.ih8mud.com
Hey everyone, I wanted to post here for the most visibility on some recent developments with my AHC adventure.
I know some of this is recapturing existing info, so bear with me. Please note that not all of this is official info and largely my own reverse engineering work.
I absolutely love having an on demand lift, but I like others here had a lot of issues with it. Although the main issue I had been chasing was a drivers side lean this post is more about what I've learned from the impact and observations in solving that which I want to talk about and share as I now know they are all interrelated to some degree. These are my findings.
I am hoping to help all of those here who are concerned and have posted about all of the following issues. Ive grouped them as best I could.
_______________________________________________________________________________________________________________________________________________________
Problems:
1 - trucks out of level
2 - premature weeping rear left shock
3 - sensor lifts / HOU never really being able to level
4 - bad ride quality
5 - little influence in ride mode damping
6 - leveled or lifted and not being able to lift or lower (refusal and no arrow on dash/ blank dash height reading)
7 - lifting and not being able to engage H on the dash DESPITE physical movement
8 - inconsistent leveling after the HOU patch or leveling out of phase with the pumps lifting (like the jerky drop)
9- why one sensor is at an odd level with its parallel side
10 - why the vehicle wont lift or lower outside of the normal safety lockouts with or without sensor adjustment
11 - Incorrect adjustment causes L to drop down, bounce of bumps and lift back angrily
12 - why does HOU refuse an adjustment when it is within a 20mm in the measured and standard input fields
^^^THIS IS A MAJOR CLUE^^^
_______________________________________________________________________________________________________________________________________________________
Let me tell you first off that I feel your pain as I've experienced just about every single one of those complaints myself. Some issues can be directly addressed and some are secondary effects of others. Lets continue.
I still can only speculate if there is any difference in the program for the AHC ECU between model years (which i think there might be) but I do know from observing others around town that many if not ALL 2016+ LXs lean to the drivers side. In my case, for a very long and frustrating year no matter what i did the car never wanted to stay level. I received some very good insider advice by total chance and beyond happy that it's now SOLVED.
_______________________________________________________________________________________________________________________________________________________
Solution 1,2,3 - Difficulty 4/5:
Swap the rear left spring. Ive posted more info here on the proper fix for that and also want to give credit where credit is due for the advice leading me down that path.
Cause:
The rear springs are different to compensate for the gas tank in right hand drive markets causing LHD vehicles to lean. This issue is exacerbated by removing the third row seats and masked when the vehicle is loaded up. This wont effect much but some odd rear axle bounce, handling nuances, and your OCD trigger (like me).
_______________________________________________________________________________________________________________________________________________________
Yesterday I did a max sensor lift (after properly sorting my level) to prepare for an alignment only to discover that H wouldn't lock in afterwards. I got really pissed off all over again with AHC and went all in and spent two hours in TechStream to figure it out. I was almost to a level of ripping it out, parting it out and installing a standard lift. Why did I do a lift in the first place? That leads us to the next quick and easy fix.
_______________________________________________________________________________________________________________________________________________________
Solution 4,5,6,7,8 - difficulty level 1/5:
If and only if you are unladen know your globes /shocks are good and still experiencing a harsh ride, the easiest way to address that would be to lift your sensors.
This is the best solution to redistribute weight from your springs back to your AHC without modifying your suspension. Only a mild sensor adjustment is needed NOT a max out. Maxing sensors will cause the inverse issue and put your suspension too far out of spec. (this can be negligible depending on your fitment and is not a catch all)
Cause:
There is too little load on the AHC system and too much on the springs. Softening up the AHC dampers doesnt have an effect since the shocks are not being actuated enough to make a difference. The springs are holding the vehicle too far out of the full shock travel range. The inverse solution to this is of course stiffer / longer springs front and rear, as well as shock spacer and trim packers when you are loading up more than the AHC is "supposed" to bear. This is a TUNED system it is vital to remember that for all LX builds. You have to treat it as such to preserve the correct synergy between AHC system/shocks and springs. Otherwise it will always be too soft or too stiff OR you could just be overworking your AHC in the long term. Perform either based on your build and needs.
_______________________________________________________________________________________________________________________________________________________
Now ever since I've balanced my load on the rear springs by height matching them, I noticed something very peculiar. My HOU adjustments which previously always either outright failed, were delayed, or only partially effective were now immediately sticking and holding without any delayed adjustment period.
Theres been a lot of discussion on lifting sensors and Height Offset Utility (HOU) and I'm confident now that there is some degree of misunderstanding and holes in our collective knowledge following the conversation here regarding AHC fine tuning procedures.
Regarding the clue on item 11 on the problems list and if you reference the FSM for the HOU you will see that there is one odd step that is often skipped. That step is jacking the vehicle level. While I was experimenting, I confirmed that a prior refusal of an input value would be accepted after adjusting another corner. I also found that multiple adjustments could be made if they were sequenced either left to right, or front to back. The FSM also advises that in an event of large discrepancies in height to perform the fronts first and then the rears. These are evidence of the hidden and inherent safety and stability logic programmed into the AHC ECU. Ive now given this way too much thought and I dont think i am overdoing it. AHC is anything but simple.
Some of the basic rules are as follows:
For each sensor height value, there is a corresponding pressure limit AND probably volume the system is looking to achieve (it needs fluid and reserves some for hidden height modes as well). Simply, if the required pressure to move the sensor is beyond the threshold, or the needed lift is beyond the shock travel limit, the truck will not lift. These points are well known but in addition to this, there is also a comparative logic that is done with a few other data points there are actually multiple levels of control on top of just the pressure.
First is the corresponding values of the adjacent sensor. This ensures the vehicle will not exceed bank angles and maintain level side to side. Second is the value of the opposite front/back left/right sensor since the pressures are X linked (thanks to @TeCKis300 on this one for his findings). Raising one corner inherently shifts load the the opposing sides and the system is preventing an indirect over/under-load of one/two wheels or one axle front back. Third the G sensor must also "authorize" the change in both an instance of checking for roll angle limits, and in another instance preventing improper adjustments if for example you are level and only one wheel is drooped to prevent setting the truck further off axis. Fourth, there are reserved bounds for all 3(4) height levels. One cannot be in a low N and ask the pressure to be removed for a drop squashing and stress the suspension components. This is all before even considering variable damping rates, speed sensors or steering angle adaptations that it must adhere to.
Given all of this, does it really make sense why we have not one but two methods of control for height adjustment?
The manual will first advise a sensor adjustment, and an HOU as a secondary to that. At any normal factory height, there is no great logical reason why HOU would even be necessary. The sensors have plenty of travel to balance a truck. Even more peculiar is when you consider there is not a single reference point of where sensor arms should be located. I was once extremely frustrated by this and i am now very thankful that we have such a wide range of play. Is the LX begging to be lifted? No, but it does seem as though Toyota gave themselves some options in tuning beyond OEM specs, perhaps due to armor market or just a gift to us or homage to the LC heritage.
This has lead me to the conclusion that HOU is only there to help calibrate the weakest link in the entire system NOT to actually help balance or move the truck at all but instead to ensure the ECU logic can function correctly. That is why it is a calculated value and not one you can simply just make up and plug in (and a very cumbersome one to do properly at that) and also why you must jack the vehicle to relieve pressure and readings while you are adjusting it. HOU utility serves as a function of the AHC ECU to remap the PRESSURE needed to achieve the correct height value of the shock against where the sensor is reading for that corner. That is the only way that i can see from my lengthy experimentation for the ECU to reference the data points it needs in order to make its decisions. It is looking for not only that specific wheel current height and pressure, but also calculating against relative measures of other sensors for both pressure and height throughout the range. If that means only one instance of height mode will be affected, it will refuse the input.
So what does HOU ACTUALLY do then? HOU, does a basic remapping of the pressure / height curve to the height sensor voltage and that is why the data list will show you the "equivalent" calculated height sensor reading of the difference between that and your actual measurements. IT IS NOT A HEIGHT LEVELING TOOL despite the FSM being worded that way. Height leveling is the job of another component... Now I mentioned a weak link earlier, in what can only be described as the most advanced and robust commercial passenger suspension sold worldwide. Can you guess what that weak link is? Let me give you a hint. Why do you think some of us have zero issues and some of us have experienced nothing but issues trying to play with the system? The answer is the height sensor itself and even maybe the links used to mount them.
The height sensors are simple mechanical potentiometers that are LOOSELY fitted in an extremely exposed location. You can actually see values bounce around as you are in the data list which to me is absolutely ridiculous in this caliber of truck. I dont want to call them crude, but thats exactly what they are. I understand that they could not make a precision custom part for this due to cost, but it only works when AHC is operating in factory parameters where all of the trucks would be set to. There is sometimes no leeway in what we are trying to do with lifting due to the lack of precision involved.
Where this has lead me more recently after solving half of the battle with my springs was to evaluate my own sensor readings. Suffice to say they are all over the place. Some of the succesful lifted LX members noted this when i reached out for help a year ago so thank you for that @radman @grinchy. You can look into some of my earlier screenshot posts where i asked due to TS not accepting my HOU inputs. Specially in my FR and RL where i not so coincidentally am having a bunch of issues. I am willing to bet good money that if you are having issues with this stuff, its because your sensors are so far out of sync with each other that the ECU will not give you any freedom. In my truck 2017 pristine condition with 60K miles, they were very far off before i even started to lose more of my hairline and touched the system. I had readings as far off as 50mm with sensors all matched. My values were already outside of 20MM adjustment range and therefore it will not allow further manipulation. That is because all of the above logic is at play. This is further proven by the disparate physical locations of the sensor arms. Even at the exact same height, the values are so far out of median range of each other that truck will refuse to lift unless i move them in opposite directions to normalize them and THEN apply HOU adjustments. That was why (along with pressure levels + springs work) that my truck would only have the full range of height mode selection when my sensors were in a very limited range on their arms where all of this math could sum check properly in the ACH ECU and none of them were aligned. Thats a huge red flag as all of them travel the same range.
_______________________________________________________________________________________________________________________________________________________
Solution 9,10,11,12 - Difficulty level 3/5:
Check and balance your sensors with techstream and the FSM. It may require removing, cleaning or even replacing them outright. You can perform the check per the instructions to see if your readings are within range however, i suspect that you will need to be more precise in matching them than even the tolerance allowed by OEM.
Cause:
The produced voltage of the potentiometer in the sensor is giving a reading too far out of bounds of the systems equivalent height calculation. A mismatch of greater than what the HOU can compensate for is causing refusal of input values or incompatible results when the sensors are used to custom lift or lower the truck.
_______________________________________________________________________________________________________________________________________________________
Many moons ago, I recall seeing Sam on youtube cleaning his sensor to fix his system. (please give me his username which i forget, you might know him from building his own slimline bumper or his badass 100). I am also hoping to get more data from the forum from anyone with techstream off your truck wether or not you have had success with it. I hope that this information is received well and if i should be so honored have a dedicated AHC Remedy thread made from this post.
I also want to remind everyone that adjusting ride height has implications outside of AHC and requires a couple of things to dial in the suspension outside of the general forum guidelines. One is the reset of the G sensor per the FSM and the other, which i have performed to great success is stabilizing all the necessary suspension links at the new N ride height and to then retorque everything after performing all of the above adjustments.
If i was really interested, which I am, i would build a custom height sensor. One that you could you adjust outside of techstream. You could do fun things like just spit out the voltage of a lower angle while you are above 18MPH. Wether or not the shock would retain pressure is a whole different story though. I dont think it would necessarily work as the ECU has to feed fluid into the shock and it may just release the valve again since it knows that pressure is above what it should be for the angle. Thats a different can of worms and I don't want to do it with my truck and would be better to just be able to crack the ECU.
Please share your feedback and any questions you may have regarding any and all of this AHC business. And thanks for reading through all of this i know its lenghty.
The forum is invaluable to me and I hope I can give back any portion of all that I have learned in my time here. If only to serve as a buffer against the negative views on AHC then i would be happy to take that since it is such a brilliant system.
Cheers and happy lifting,
-Mal
I know some of this is recapturing existing info, so bear with me. Please note that not all of this is official info and largely my own reverse engineering work.
I absolutely love having an on demand lift, but I like others here had a lot of issues with it. Although the main issue I had been chasing was a drivers side lean this post is more about what I've learned from the impact and observations in solving that which I want to talk about and share as I now know they are all interrelated to some degree. These are my findings.
I am hoping to help all of those here who are concerned and have posted about all of the following issues. Ive grouped them as best I could.
_______________________________________________________________________________________________________________________________________________________
Problems:
1 - trucks out of level
2 - premature weeping rear left shock
3 - sensor lifts / HOU never really being able to level
4 - bad ride quality
5 - little influence in ride mode damping
6 - leveled or lifted and not being able to lift or lower (refusal and no arrow on dash/ blank dash height reading)
7 - lifting and not being able to engage H on the dash DESPITE physical movement
8 - inconsistent leveling after the HOU patch or leveling out of phase with the pumps lifting (like the jerky drop)
9- why one sensor is at an odd level with its parallel side
10 - why the vehicle wont lift or lower outside of the normal safety lockouts with or without sensor adjustment
11 - Incorrect adjustment causes L to drop down, bounce of bumps and lift back angrily
12 - why does HOU refuse an adjustment when it is within a 20mm in the measured and standard input fields
^^^THIS IS A MAJOR CLUE^^^
_______________________________________________________________________________________________________________________________________________________
Let me tell you first off that I feel your pain as I've experienced just about every single one of those complaints myself. Some issues can be directly addressed and some are secondary effects of others. Lets continue.
I still can only speculate if there is any difference in the program for the AHC ECU between model years (which i think there might be) but I do know from observing others around town that many if not ALL 2016+ LXs lean to the drivers side. In my case, for a very long and frustrating year no matter what i did the car never wanted to stay level. I received some very good insider advice by total chance and beyond happy that it's now SOLVED.
_______________________________________________________________________________________________________________________________________________________
Solution 1,2,3 - Difficulty 4/5:
Swap the rear left spring. Ive posted more info here on the proper fix for that and also want to give credit where credit is due for the advice leading me down that path.
Cause:
The rear springs are different to compensate for the gas tank in right hand drive markets causing LHD vehicles to lean. This issue is exacerbated by removing the third row seats and masked when the vehicle is loaded up. This wont effect much but some odd rear axle bounce, handling nuances, and your OCD trigger (like me).
_______________________________________________________________________________________________________________________________________________________
Yesterday I did a max sensor lift (after properly sorting my level) to prepare for an alignment only to discover that H wouldn't lock in afterwards. I got really pissed off all over again with AHC and went all in and spent two hours in TechStream to figure it out. I was almost to a level of ripping it out, parting it out and installing a standard lift. Why did I do a lift in the first place? That leads us to the next quick and easy fix.
_______________________________________________________________________________________________________________________________________________________
Solution 4,5,6,7,8 - difficulty level 1/5:
If and only if you are unladen know your globes /shocks are good and still experiencing a harsh ride, the easiest way to address that would be to lift your sensors.
This is the best solution to redistribute weight from your springs back to your AHC without modifying your suspension. Only a mild sensor adjustment is needed NOT a max out. Maxing sensors will cause the inverse issue and put your suspension too far out of spec. (this can be negligible depending on your fitment and is not a catch all)
Cause:
There is too little load on the AHC system and too much on the springs. Softening up the AHC dampers doesnt have an effect since the shocks are not being actuated enough to make a difference. The springs are holding the vehicle too far out of the full shock travel range. The inverse solution to this is of course stiffer / longer springs front and rear, as well as shock spacer and trim packers when you are loading up more than the AHC is "supposed" to bear. This is a TUNED system it is vital to remember that for all LX builds. You have to treat it as such to preserve the correct synergy between AHC system/shocks and springs. Otherwise it will always be too soft or too stiff OR you could just be overworking your AHC in the long term. Perform either based on your build and needs.
_______________________________________________________________________________________________________________________________________________________
Now ever since I've balanced my load on the rear springs by height matching them, I noticed something very peculiar. My HOU adjustments which previously always either outright failed, were delayed, or only partially effective were now immediately sticking and holding without any delayed adjustment period.
Theres been a lot of discussion on lifting sensors and Height Offset Utility (HOU) and I'm confident now that there is some degree of misunderstanding and holes in our collective knowledge following the conversation here regarding AHC fine tuning procedures.
Regarding the clue on item 11 on the problems list and if you reference the FSM for the HOU you will see that there is one odd step that is often skipped. That step is jacking the vehicle level. While I was experimenting, I confirmed that a prior refusal of an input value would be accepted after adjusting another corner. I also found that multiple adjustments could be made if they were sequenced either left to right, or front to back. The FSM also advises that in an event of large discrepancies in height to perform the fronts first and then the rears. These are evidence of the hidden and inherent safety and stability logic programmed into the AHC ECU. Ive now given this way too much thought and I dont think i am overdoing it. AHC is anything but simple.
Some of the basic rules are as follows:
For each sensor height value, there is a corresponding pressure limit AND probably volume the system is looking to achieve (it needs fluid and reserves some for hidden height modes as well). Simply, if the required pressure to move the sensor is beyond the threshold, or the needed lift is beyond the shock travel limit, the truck will not lift. These points are well known but in addition to this, there is also a comparative logic that is done with a few other data points there are actually multiple levels of control on top of just the pressure.
First is the corresponding values of the adjacent sensor. This ensures the vehicle will not exceed bank angles and maintain level side to side. Second is the value of the opposite front/back left/right sensor since the pressures are X linked (thanks to @TeCKis300 on this one for his findings). Raising one corner inherently shifts load the the opposing sides and the system is preventing an indirect over/under-load of one/two wheels or one axle front back. Third the G sensor must also "authorize" the change in both an instance of checking for roll angle limits, and in another instance preventing improper adjustments if for example you are level and only one wheel is drooped to prevent setting the truck further off axis. Fourth, there are reserved bounds for all 3(4) height levels. One cannot be in a low N and ask the pressure to be removed for a drop squashing and stress the suspension components. This is all before even considering variable damping rates, speed sensors or steering angle adaptations that it must adhere to.
Given all of this, does it really make sense why we have not one but two methods of control for height adjustment?
The manual will first advise a sensor adjustment, and an HOU as a secondary to that. At any normal factory height, there is no great logical reason why HOU would even be necessary. The sensors have plenty of travel to balance a truck. Even more peculiar is when you consider there is not a single reference point of where sensor arms should be located. I was once extremely frustrated by this and i am now very thankful that we have such a wide range of play. Is the LX begging to be lifted? No, but it does seem as though Toyota gave themselves some options in tuning beyond OEM specs, perhaps due to armor market or just a gift to us or homage to the LC heritage.
This has lead me to the conclusion that HOU is only there to help calibrate the weakest link in the entire system NOT to actually help balance or move the truck at all but instead to ensure the ECU logic can function correctly. That is why it is a calculated value and not one you can simply just make up and plug in (and a very cumbersome one to do properly at that) and also why you must jack the vehicle to relieve pressure and readings while you are adjusting it. HOU utility serves as a function of the AHC ECU to remap the PRESSURE needed to achieve the correct height value of the shock against where the sensor is reading for that corner. That is the only way that i can see from my lengthy experimentation for the ECU to reference the data points it needs in order to make its decisions. It is looking for not only that specific wheel current height and pressure, but also calculating against relative measures of other sensors for both pressure and height throughout the range. If that means only one instance of height mode will be affected, it will refuse the input.
So what does HOU ACTUALLY do then? HOU, does a basic remapping of the pressure / height curve to the height sensor voltage and that is why the data list will show you the "equivalent" calculated height sensor reading of the difference between that and your actual measurements. IT IS NOT A HEIGHT LEVELING TOOL despite the FSM being worded that way. Height leveling is the job of another component... Now I mentioned a weak link earlier, in what can only be described as the most advanced and robust commercial passenger suspension sold worldwide. Can you guess what that weak link is? Let me give you a hint. Why do you think some of us have zero issues and some of us have experienced nothing but issues trying to play with the system? The answer is the height sensor itself and even maybe the links used to mount them.
The height sensors are simple mechanical potentiometers that are LOOSELY fitted in an extremely exposed location. You can actually see values bounce around as you are in the data list which to me is absolutely ridiculous in this caliber of truck. I dont want to call them crude, but thats exactly what they are. I understand that they could not make a precision custom part for this due to cost, but it only works when AHC is operating in factory parameters where all of the trucks would be set to. There is sometimes no leeway in what we are trying to do with lifting due to the lack of precision involved.
Where this has lead me more recently after solving half of the battle with my springs was to evaluate my own sensor readings. Suffice to say they are all over the place. Some of the succesful lifted LX members noted this when i reached out for help a year ago so thank you for that @radman @grinchy. You can look into some of my earlier screenshot posts where i asked due to TS not accepting my HOU inputs. Specially in my FR and RL where i not so coincidentally am having a bunch of issues. I am willing to bet good money that if you are having issues with this stuff, its because your sensors are so far out of sync with each other that the ECU will not give you any freedom. In my truck 2017 pristine condition with 60K miles, they were very far off before i even started to lose more of my hairline and touched the system. I had readings as far off as 50mm with sensors all matched. My values were already outside of 20MM adjustment range and therefore it will not allow further manipulation. That is because all of the above logic is at play. This is further proven by the disparate physical locations of the sensor arms. Even at the exact same height, the values are so far out of median range of each other that truck will refuse to lift unless i move them in opposite directions to normalize them and THEN apply HOU adjustments. That was why (along with pressure levels + springs work) that my truck would only have the full range of height mode selection when my sensors were in a very limited range on their arms where all of this math could sum check properly in the ACH ECU and none of them were aligned. Thats a huge red flag as all of them travel the same range.
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Solution 9,10,11,12 - Difficulty level 3/5:
Check and balance your sensors with techstream and the FSM. It may require removing, cleaning or even replacing them outright. You can perform the check per the instructions to see if your readings are within range however, i suspect that you will need to be more precise in matching them than even the tolerance allowed by OEM.
Cause:
The produced voltage of the potentiometer in the sensor is giving a reading too far out of bounds of the systems equivalent height calculation. A mismatch of greater than what the HOU can compensate for is causing refusal of input values or incompatible results when the sensors are used to custom lift or lower the truck.
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Many moons ago, I recall seeing Sam on youtube cleaning his sensor to fix his system. (please give me his username which i forget, you might know him from building his own slimline bumper or his badass 100). I am also hoping to get more data from the forum from anyone with techstream off your truck wether or not you have had success with it. I hope that this information is received well and if i should be so honored have a dedicated AHC Remedy thread made from this post.
I also want to remind everyone that adjusting ride height has implications outside of AHC and requires a couple of things to dial in the suspension outside of the general forum guidelines. One is the reset of the G sensor per the FSM and the other, which i have performed to great success is stabilizing all the necessary suspension links at the new N ride height and to then retorque everything after performing all of the above adjustments.
If i was really interested, which I am, i would build a custom height sensor. One that you could you adjust outside of techstream. You could do fun things like just spit out the voltage of a lower angle while you are above 18MPH. Wether or not the shock would retain pressure is a whole different story though. I dont think it would necessarily work as the ECU has to feed fluid into the shock and it may just release the valve again since it knows that pressure is above what it should be for the angle. Thats a different can of worms and I don't want to do it with my truck and would be better to just be able to crack the ECU.
Please share your feedback and any questions you may have regarding any and all of this AHC business. And thanks for reading through all of this i know its lenghty.
The forum is invaluable to me and I hope I can give back any portion of all that I have learned in my time here. If only to serve as a buffer against the negative views on AHC then i would be happy to take that since it is such a brilliant system.
Cheers and happy lifting,
-Mal
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First off, thanks to everyone who has contributed to this thread and all the other threads.
My 16' Lx has the sensor lift and is now pretty heavy with armor, drawers, ext. My AHC works great and I really don't have any complaints about the system in general. However, I have definitely noticed that the ride is really stiff and terrible in High. I now off-road in the regular height setting unless I need the clearance, then I put it in high and then switch back to N when Im past the obstacle.
I know for sure that I load my truck up beyond the payload capacity, and that makes me kind of nervous. I have been thinking about doing some of the proposed options to help unload the AHC by stiffening the springs by replacing them or adding spacers. I called Slee about another project and asked them about it and the opinion the Slee employee gave me was that adding a spacer to the springs would not do much to unload the AHC as the springs are already really soft so that the truck can lower. His advice was either to leave it as is or replace the whole system.
I was one of the folks that had my AHC fail after the dealership did an AHC flush, there is a whole thread about it. Basically the dealership took about a month to sort it out and ended up replacing the AHC pump. Now that my AHC is working, I am nervous to touch it again. I honestly think I will run it as is until it dies or I sell the truck. After that AHC flush debacle, it seems like its best to avoid anymore frustration by not touching it. Thoughts?
My 16' Lx has the sensor lift and is now pretty heavy with armor, drawers, ext. My AHC works great and I really don't have any complaints about the system in general. However, I have definitely noticed that the ride is really stiff and terrible in High. I now off-road in the regular height setting unless I need the clearance, then I put it in high and then switch back to N when Im past the obstacle.
I know for sure that I load my truck up beyond the payload capacity, and that makes me kind of nervous. I have been thinking about doing some of the proposed options to help unload the AHC by stiffening the springs by replacing them or adding spacers. I called Slee about another project and asked them about it and the opinion the Slee employee gave me was that adding a spacer to the springs would not do much to unload the AHC as the springs are already really soft so that the truck can lower. His advice was either to leave it as is or replace the whole system.
I was one of the folks that had my AHC fail after the dealership did an AHC flush, there is a whole thread about it. Basically the dealership took about a month to sort it out and ended up replacing the AHC pump. Now that my AHC is working, I am nervous to touch it again. I honestly think I will run it as is until it dies or I sell the truck. After that AHC flush debacle, it seems like its best to avoid anymore frustration by not touching it. Thoughts?
How much did you lift?
AHC basically handles the entire load of the vehicle and then some otherwise it wouldn't lift. The springs work in conjunction with it and less so the higher you lift.
If you graphed the two bearings for a lack of better word, there would be a sweet spot established. When loaded up the best thing you can do IMO is to reestablish that convergence range by upgrading your springs. I know there are a plethora of options for rears but im not sure on the fronts. I will defer to the forum experts on what they recommend but I just wanted to say don't shy away from upgrading. It's only the other way around that increases stress on AHC. Add too much and ride control will have less and less effect on damping but no harm to AHC.
I made my post largely to demystify some of the system and I am always amazed by how much can be had out of it. Im just now beginning to realize i want to modify it rather than leaving it alone, like you are worried about.
I have very little real world data to argue, but I don't agree with your assessment of the HOU. I agree that it is regularly used improperly to lift the truck, but I think when some users are patient enough with it they end up fumbling to where they are supposed to be.
I think you are giving way too much credit to how the system is controlling height. It is simply using the height sensors. It's possible that there are hidden sensors in all the components you are talking about, but where is the reference in FSM or wiring to back that up? There is only one pressure sensor in the system at the pump.
The FSM shows you exactly how to enter data into the HOU, but no one follows it because it's cumbersome. The point of leveling the truck with jacks isn't to "relieve pressure" so the system can work. It's so the truck can take a reading of how much you had to move the truck to get it level by way of the "heigh after adjust" value. That's why the manual says to get everything back to 0 (leaving truck in neutral and bouncing the corners) then has you level the truck with jacks. This effects the "after height adjust" values in Techstream that are used in the equation to decide whether the HOU is going to make an adjustment.
I agree with a lot of what you are saying about keeping the system balanced so the proper heft of the vehicle is being managed by AHC and not just springs or vice versa.
My understanding is that you move sensors to get it close, and if it's not close enough, you use HOU following the FSM to get leveling closer.
Ultimately the left to right "levelness" of the truck still relies on the springs and weight of the truck being level, because each axle is hydraulically tied together in the AHC system and the sides of each axle will share fluid during driving, so even if you make static changes, they will go away once you drive and the leveling gates are opened.
The cross linking does allow one corner to affect the pressure on the other 3 corners, but that system only push/pulls on the other corners, it does not share hydraulic pressure like the corners of each axle does.
I"ll say that, these are just my expectations from what work I've done with my AHC system and from reading through the FSM and system description fairly extensively. I've yet to go out and spend an afternoon proving, so i could be completely off base.
I think you are giving way too much credit to how the system is controlling height. It is simply using the height sensors. It's possible that there are hidden sensors in all the components you are talking about, but where is the reference in FSM or wiring to back that up? There is only one pressure sensor in the system at the pump.
The FSM shows you exactly how to enter data into the HOU, but no one follows it because it's cumbersome. The point of leveling the truck with jacks isn't to "relieve pressure" so the system can work. It's so the truck can take a reading of how much you had to move the truck to get it level by way of the "heigh after adjust" value. That's why the manual says to get everything back to 0 (leaving truck in neutral and bouncing the corners) then has you level the truck with jacks. This effects the "after height adjust" values in Techstream that are used in the equation to decide whether the HOU is going to make an adjustment.
I agree with a lot of what you are saying about keeping the system balanced so the proper heft of the vehicle is being managed by AHC and not just springs or vice versa.
My understanding is that you move sensors to get it close, and if it's not close enough, you use HOU following the FSM to get leveling closer.
Ultimately the left to right "levelness" of the truck still relies on the springs and weight of the truck being level, because each axle is hydraulically tied together in the AHC system and the sides of each axle will share fluid during driving, so even if you make static changes, they will go away once you drive and the leveling gates are opened.
The cross linking does allow one corner to affect the pressure on the other 3 corners, but that system only push/pulls on the other corners, it does not share hydraulic pressure like the corners of each axle does.
I"ll say that, these are just my expectations from what work I've done with my AHC system and from reading through the FSM and system description fairly extensively. I've yet to go out and spend an afternoon proving, so i could be completely off base.
From your pictures (love your truck by the way), it looks like you have a pretty "serious" sensor lift. I'd imagine that between the weight and your "N" height being so high, you are getting to the edge of the system capabilities once you try to go into high mode. You have a newer truck (fresh globes), so most likely the system handles the height fine, but at that point you are barely using the springs to carry any load because you are so high.
I agree with this statement. The FSM actually gives you the fixed values for front/rear, but they arent needed if you just offset your own values by the desired difference. That being said, sometimes the HOU simply doesnt like your values and you to pick something different.
None of that relies on any sensors, this is all done in the ECU.
If you look at the way the system is built, the matrix valving does exactly that. How else could one single shock be pressurized?
Thats like saying how would the system know youre overloaded if theres no weight sensor. It doesn't need that since it was designed brilliantly.
In fact, through the active test, you can see and address all of the valves, gates, and shocks independantly. Just because you don't see it working doesn't mean its not there. Also what would be the point in jacking anything to level when you are already provided the standard values in the FSM?
All that HOU is supposed to really do is fix the poor sensor calibration.
Ive spent considerable time with this, and have verified everything i wrote myself. Im sorry but its just not that simple.
I addressed that specifically as well. Its much more complicated than that.
I plan to go ab
I plan to go back and read your post again, but I can fire up TS and change all my hou values to -.8 and I will drop by 1.5”.
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There are 6 valves in total that affect height. One for each corner and a gate valve on each axle. The truck can affect the height of one wheel by closing all valves except the level valve for the corner it wants to move. Now this is only in static operation, because once the truck starts moving at some point (maybe even before it moves as that is the mystery in the programming) it opens the gate valve and then the pressure between the two corners on an axle will balance out, leaving only the springs and weight balance to determine how level the vehicle is.
I don't understand, the truck clearly has sensors, and the ECU can't make decisions without data from them.
I don't see the correlation. The system doesn't "know you're overloaded". If it did it wouldn't even try to lift, it would just tell you you are overloaded. The system attempts to do what you asked it to do, and once it's can't fulfill the request, it does the best it can and stops.
I don't know the reasoning for why they made the HOU system the way they did. I know it is inherently designed the way it is to help dial in height adjustments for two reasons, one to get the balance between spring and AHC system correct and two, so that left to right height is close enough that when a gate valve opens there isn't a major slide in pressure from one side to the other as pressure equalizes. It's not there to raise or lower by design but just to get each side to a pretty even height. As long as your height after adjust values are 0, then whatever values you enter in the HOU should move the height based on the offset between the two values entered. If the height after adjust values are not zero when entering the data, then all bets are off.
AHC is pretty well documented in the FSM, the only real mysteries are the calculations and decisions the ECU makes. The number of sensors, valves, pumps, actuators etc... are all enumerated.
Thanks for the reply but i believe you are answering a rhetorical question regarding the single shock. I wasn't asking, but i was addressing your claim of asking how the system could figure out a pressure of an indvidual shock with one pressure sensor. I think you missed that point.
When i write, i tend to form long sentences. Not intentionally but in order to keep everything coherent and dense. Sorry about that.
I think you have a firm grasp of AHC mechanics, which I also do maybe not to an extent that ive now done with the AHC ECU.
But I think we are muddying the point a bit though and I don't want to get off topic.
This is more about how to solve problems that have not been solvable until now.
We can leave opinions aside for the sake of the thread and those who gave up on lifting due to the multitude of problems I listed.
If you have a solution to some of them, please contribute to solving them. AHC has been out for 13 years and there has not been a comprehensive solution found that addresses everything I have. I don't want to make assures since i know the ECU itself can be bad, but if you follow though my steps with a little less skepticism i think you will find that it can really simplify a lot of the "mystery" to AHC.
It doesn't do anyone any good to argue about what the intent was of HOU, but even if that was the case, your claim leaves way too many unanswered questions to satisfy my level of understanding. Ive made a very solid case for everything i said and I am completely confident in that since I've rectified almost all of my issues. When i discussed this with those who have done the lift and asked these same questions when i was unsuccessful, i was not afforded the luxury of a single solution. Not everyone has nicely paired sensors and a lot of what seems easy for some is impossible for others. We can get past that now.
Have a nice day.
