Having trouble with height control and AHC in general. Can't adjust heigth or change between sport and comfort mode. Anyone had this problem before??
LX470 AHC Problems
- Thread starter fish933
- Start date
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Are you having trouble moving the dial from comfort to sport, or in noticing a difference when you have made the change?
The AHC will go up or down when all doors are closed. It will do so in drive if the speed is slow enough, and when stopped, if the brake has not been on too long. It will also work in P without the parking brake on, as long as all doors are closed.
The AHC will go up or down when all doors are closed. It will do so in drive if the speed is slow enough, and when stopped, if the brake has not been on too long. It will also work in P without the parking brake on, as long as all doors are closed.
- Thread starter
- #4
LX Pearl and Joe422, Currently the 'off' lamp is blinking constantly and the 'L' lamp is illuminated constantly. If I press the 'off' button next to the gear stick nothing happens. If I press the button to raise the vehicle the 'N' lamp illumintes momentarily then goes out. I have tried this with doors closed and park brake on and not pressure on the foot brake.
Also changing the suspension mode from comfort to sport has no effect. The suspension is currently stuck and is very, very stiff.
i have had the computer scanned by Toyota and by another mechanic. Toyota scans provided codes of c1718 and c1762 but gave no definition of the codes. The mechanic's scan gave the codes c1751 (continuous current to compressor) and c1762 (abnormal oil pressure to pump). I have had a Autoelectrician look at it. He got the pump to spin but no fluid flowed out of it. The reservoir is also overly full. I don't know if this is because all fluid has returned to the tank or because it is over filled.
Any ideas??? I have been scanning the net for a workshop manual for the LX470 2000 model. Do you guys know any links? Thanks
Also changing the suspension mode from comfort to sport has no effect. The suspension is currently stuck and is very, very stiff.
i have had the computer scanned by Toyota and by another mechanic. Toyota scans provided codes of c1718 and c1762 but gave no definition of the codes. The mechanic's scan gave the codes c1751 (continuous current to compressor) and c1762 (abnormal oil pressure to pump). I have had a Autoelectrician look at it. He got the pump to spin but no fluid flowed out of it. The reservoir is also overly full. I don't know if this is because all fluid has returned to the tank or because it is over filled.
Any ideas??? I have been scanning the net for a workshop manual for the LX470 2000 model. Do you guys know any links? Thanks
Fish933... your symptoms seem very close to what I had... but a few differences...
I had the same blinking 'off' light and level was often defaulted to low position. If I try to change height, then I could hear the pump spinning (something I realized you should barely be able to hear). I had these conditions ater changing the Actuator spheres, and replaced front shocks. First few times I bled raised and bled the system, it seemed fine... and fluid level was perfect... but after a test drive, the fluid tank was strangely high... maybe an inch higher level than the max line. Back at my driveway, I got the blinking 'Off' and the truck slowly sank.
I stuck a jumper wire into the diagnostics connector to manually activate the AHC pump. There was no fluid movement whatsoever.... but I knew the pump motor was running. After reading BonS' experience, I gave it a shot and ordered the Pump sub-assembly. (list price is $291.. but i'm sure you can find cheaper). It was an easy swap, and after that the fluid self primed, and the LX was sitting sky high again. A few rounds of bleeding, and 2 can sof fluid gave me a nice ride again... and the height works perfectly, smoothly, and silently.
I don't know if your ride quality got stiff because of the pump (definitely possible) or if the Actuator speres went bad (common)... but the blinking 'OFF' light, spinning motor, no response, high fluid tank level, no fluid movement, and abnormal fluid pressure (too low?) would in my opinion, indicate your pump went bad... and aparently, they do. This part is much cheaper than actuators, shocks, etc, and if you got some high miles, or used the AHC a lot, then I'd definitely recommend changing it.
If you do choose to try this route...
-------------------------------------------------
48901-60010 Pump Sub-Assy
90301-70003 O-ring (big)
90301-06012 O-ring (small)
optional:
90311-10001 Oil Seal (motor) <--- not a must, but very easy to change... and just couple $$. I'd say it's worth it
04977-60010 Motor/pump coupler <---- not a must, but less than $1.50
08886-01805 AHC fluid 2.5L (x2 cans)
Good luck!~
-Joe
I had the same blinking 'off' light and level was often defaulted to low position. If I try to change height, then I could hear the pump spinning (something I realized you should barely be able to hear). I had these conditions ater changing the Actuator spheres, and replaced front shocks. First few times I bled raised and bled the system, it seemed fine... and fluid level was perfect... but after a test drive, the fluid tank was strangely high... maybe an inch higher level than the max line. Back at my driveway, I got the blinking 'Off' and the truck slowly sank.
I stuck a jumper wire into the diagnostics connector to manually activate the AHC pump. There was no fluid movement whatsoever.... but I knew the pump motor was running. After reading BonS' experience, I gave it a shot and ordered the Pump sub-assembly. (list price is $291.. but i'm sure you can find cheaper). It was an easy swap, and after that the fluid self primed, and the LX was sitting sky high again. A few rounds of bleeding, and 2 can sof fluid gave me a nice ride again... and the height works perfectly, smoothly, and silently.
I don't know if your ride quality got stiff because of the pump (definitely possible) or if the Actuator speres went bad (common)... but the blinking 'OFF' light, spinning motor, no response, high fluid tank level, no fluid movement, and abnormal fluid pressure (too low?) would in my opinion, indicate your pump went bad... and aparently, they do. This part is much cheaper than actuators, shocks, etc, and if you got some high miles, or used the AHC a lot, then I'd definitely recommend changing it.
If you do choose to try this route...
-------------------------------------------------
48901-60010 Pump Sub-Assy
90301-70003 O-ring (big)
90301-06012 O-ring (small)
optional:
90311-10001 Oil Seal (motor) <--- not a must, but very easy to change... and just couple $$. I'd say it's worth it
04977-60010 Motor/pump coupler <---- not a must, but less than $1.50
08886-01805 AHC fluid 2.5L (x2 cans)
Good luck!~
-Joe
- Thread starter
- #6
Sorry for the late response guys - busy doing other stuff.
Have just read some good info from a LX470 manual about the suspension system and it says there is a way of putting the suspension control ECU into test mode and from here you can check the function of each sensor. It says refer to Lexus LX470 Repair Manual (Pub. No. RM618E).
Does anyone have any info on getting it into test mode or the above manual? Or some basic tests that can be done on each of the sensors- solenoids, pump pressure sensor, pump temp sensor, gate valves, etc?? Any tips appreciated!
Thanks
Have just read some good info from a LX470 manual about the suspension system and it says there is a way of putting the suspension control ECU into test mode and from here you can check the function of each sensor. It says refer to Lexus LX470 Repair Manual (Pub. No. RM618E).
Does anyone have any info on getting it into test mode or the above manual? Or some basic tests that can be done on each of the sensors- solenoids, pump pressure sensor, pump temp sensor, gate valves, etc?? Any tips appreciated!
Thanks
Trouble with AHC
I am a complete NEWBIE at this
and need some help... I bought a used 2000 LX 470 and love it, except for the AHC trouble. It labors to get into H, and if I load 7 people in the vehicle it drops to L, and wont even raise back to N. Am I correct to conclude I need to change the pump sub assembly and o rings? I have been reading some different posts here, I am however somewhat confused, so if anyone can help me out that would be greatly appreciated!
I am a complete NEWBIE at this
and need some help... I bought a used 2000 LX 470 and love it, except for the AHC trouble. It labors to get into H, and if I load 7 people in the vehicle it drops to L, and wont even raise back to N. Am I correct to conclude I need to change the pump sub assembly and o rings? I have been reading some different posts here, I am however somewhat confused, so if anyone can help me out that would be greatly appreciated!
Sounds like time for an OME or Ironman suspension upgrade. 
uHu
Bridgeburner
Sounds like you have to do two things if you want to keep the AHC:
1 Change the rear coil springs
and
2 adjust the front torsion bar springs.
The AHC (i.e. gas springs/spheres and shocks) is supposed to lift only a part of the weight. As the years pass, the steel spring weakens, and the AHC gets more work. This has to be compensated. The way to know for sure (I am already) is to measure the Neutral Pressure, to see how much the AHC is carrying at Normal height with an empty vehicle.
Another thing is that when it is so heavy for the gas spheres that the pump can not lift the truck, your gas spheres will be having a hard time, and wear faster than normal.
Well, looks like we've all figured out the reasonable service life of AHC, 10 years.
LXoffroad, what you are describing with 7 people may be by design and completely normal. See the section "Starting and Driving" about AHC in your owners manual (for '05 it's on p.273). You can search here for text in your owners manual: https://secure.drivers.lexus.com/lexusdrivers/info/my-lexus/resources/owners-manual-search.do
Here's the excerpt:
"The vehicle height cannot be raised if the vehicle load exceeds the following limits:
- up to 4 occupants [150lb per person] pluls about 660 lb in normal mode
- up to 4 occupants plus about 375 lb in the high mode
If the above load capacity is exceeded, the desired vehicle height may not be obtained even if the height select switch is pushed. (If the vehicle height cannot be raised in the normal mode and the height control indicator indicates "LO", this is because the vehicle is loaded too heavily. Under these conditions, drive your vehicle with due care.)
If the vehicle height cannot be raised even after unloading, push the height select switch on the "down arrow" side and then on the "up arrow" side. If this does not work, turn off the ignition once and then turn on. Operate the select switch again.
"
Read that full section for additional caveats. Also, when towing, same condition can occur and it's "ok" to drive that way, just with added caution (the question has come up on the forum about towing in L mode etc.). At the same time the manual does describe using caution when in L mode.
Bottom line - according to the info above, if you were in Normal mode and had 4x150 + 661 lbs = 1261 lbs of passengers + additional load you wouldn't be able to raise into H, and if you were above that weight, I guess you could go into L. To put that into perspective, 1261/7 = 180lbs per person average. Was it possible you had 7 full size adults at > 180lbs per person on average?
I wouldn't worry about a 7 passenger anomoly unless you think they were clearly under 150 each avg and you have no heavy items on the car (aftermarket bumpers etc), then I'd be concerned, or if you often carry that many people.
You also pointed out about the pump straining to go into H mode? The FSM says up to 15 seconds to raise vehicle, and up to 10 seconds to go down. So if you hear straining or if it's taking longer than 15 seconds to go up then maybe you have a problem, but if it's within that time frame, you may not have any issues at all.
Also, safest thing is to check for AHC trouble codes - you can't just use the regular OBDII scanner, you will need to follow the procedure in the FSM to check the AHC codes or you need a mechanic/dealership to use the Toyota/Lexus handheld tester or TechStream to check for the DTC codes.
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Sorry for the long post, but realize you're at a crossroads here.
Here are some questions I would ask:
Are you able to spend some serious dough having it diagnosed and fixed?
How much do you care about the AHC feature and capability?
Are you looking for the cheapest solution?
Are you looking for a reliable, cost effective suspension?
Are you comfortable/willing to try diagnosing and fixing yourself?
How urgently/quickly do you need all this fixed?
If money is no object and you love AHC, then take it to the dealership or your trusted indpendant Toyo/Lex shop, pay up to a few grand and (hopefully) walk away happy with your ahc fixed.
If you don't care about AHC or are fed up with the issues you are experiencing, you can swap out your suspension for stock LC or OME etc...
If you have time, don't mind getting your hands dirty, and want the least expensive option then try troubleshooting yourself - start by buying the FSM (cheaper pdf copies available on ebay or other online sources).
As JOE422 mentioned, looks like the most likely candidate is your pump, but it also could be a disconnected height connector, or clogged fluid line, or some other electrical issue etc. Replacing the pump and related cheap parts that JOE422 mentioned would be a good place to start and could end up being surprisingly easy and cheap.
However, if you really don't care about AHC and you're just looking for the cheapest most reliable most sensible long term solution I would suggest just swapping out the suspension. At 10 years you may replace the pump for say 250 and then realize you need another part... and another part... and b/f you know it you're in for as much as the LC or OME suspension swap would have costed (accumulators alone are 1600 for your cheapest B&B option or more like 2k for the oem parts not including labor - and realize that while you may have flat accumulators, you definitely have some other problem b/c flat accumulators do not cause your AHC trouble codes and do not cause Off light to blink).
To help get you started troubleshooting if you so choose, here are some of the "tips" from the FSM regarding your trouble codes:
1751 - when the rise control completion condition has not consisted in spite of turning on electricity to the relay for the following period of time Lo -> N 85 seconds, N -> hi 100 seconds.
Trouble area:
ahc pump & motor
ahc pump and motor circuit
ahc motor relay
height control sensor link comes off
fluid leakage from the fluid line or each solenoid valve
fluid clog in the fluid line or each solenoid valve
torsion bar spring
1718 - either 1 or 2 is detected:
1) when detecting the abnormal signal from the fluid pressure sensor for every .01 sec and that condition continued for 1 sec
2) while the motor relay is non operating, the condition that the fluid pressure exceeds 1MPa continued for 10 secs.
Trouble area:
fluid pressure sensor
fluid pressure sensor circuit
ECU
1762: either 1 or 2 is detected:
1) while the motor relay is in operation, the condition that the fluid pressure is less than .5mpa continued for .6 sec
2) when the pump motor is in delivering condition, the delivery portion does not change and the fluid pressure change is small.
Trouble area:
ahc pump and motor
fluid presure sensor
ahc motor relay
fluid empty
Thanks to All of you for your help!
I have an appointment to bring it in to a Lexus/Toyo specialist, so I'll hopefully find something more out then with that special Techstream gizmo. Agaisin thanks for that info and link! Uhu, you mentioned measuring the neutral pressure, How? and what should this be? I am not opposed to a conversion aftermarket suspension (nice touch Brock) I just would have questions about ride quality or other safety issues, like does the AHC have any safety values regarding rollover???
Is there a particular system that works best for this vehicle, in terms of maintaining a plush on road ride and gives good stability/handling on trails? I'm not (at this point) looking for serious off roading, just the occasional off road excursion. Which actually brings me to another question... Tires and wheels. I have the stock 16" with Michelin LTX's, the tires need to be replaced, and I'm thinking about going to an 18" wheel with ???tires
Any recommendations?
I have an appointment to bring it in to a Lexus/Toyo specialist, so I'll hopefully find something more out then with that special Techstream gizmo
. Agaisin thanks for that info and link! Uhu, you mentioned measuring the neutral pressure, How? and what should this be? I am not opposed to a conversion aftermarket suspension (nice touch Brock) I just would have questions about ride quality or other safety issues, like does the AHC have any safety values regarding rollover??? Is there a particular system that works best for this vehicle, in terms of maintaining a plush on road ride and gives good stability/handling on trails? I'm not (at this point) looking for serious off roading, just the occasional off road excursion. Which actually brings me to another question... Tires and wheels. I have the stock 16" with Michelin LTX's, the tires need to be replaced, and I'm thinking about going to an 18" wheel with ???tires
Any recommendations?
Thanks to All of you for your help!
I have an appointment to bring it in to a Lexus/Toyo specialist, so I'll hopefully find something more out then with that special Techstream gizmo
Is there a particular system that works best for this vehicle, in terms of maintaining a plush on road ride and gives good stability/handling on trails? I'm not (at this point) looking for serious off roading, just the occasional off road excursion. Which actually brings me to another question... Tires and wheels. I have the stock 16" with Michelin LTX's, the tires need to be replaced, and I'm thinking about going to an 18" wheel with ???tires
Based on my experience converting my 99 LX to stock LC springs/tbars/shocks:
Ride Comfort:
The ride is significantly firmer with the stock LC suspension, compared to LX AHC in "Normal" or especially "Comfort" modes. The difference is most pronounced with the rear suspension.
I would not term the stock LC ride "plush". It is about as firm as my 2002 Accord now, more or less. If you like the way something like that rides, you will prefer the stock LC suspension vs. AHC. (My 19 year old son likes it.) The plush ride of the AHC entails a much higher cost ($+time) over the life of the vehicle, which is why I converted to non-AHC.
Roll Control:
Using the stock LX Stabilizer Bar with stock LC springs/tbars/shocks, the roll control seems about the same as it was with the LX, more or less.
I was concerned about this prior to converting, but I have no issues with it. It is acceptable IMO.
Keep in mind: According to the FSM, The LX AHC system is designed to couple the hydraulic pressures of the LF-to-RF, and the LR-to-RR, except when (steering angle and/or vehicle speed) are greater in a turn. At higher turn rates/accelerations, the system decouples the hydraulic pressures from each other and also varies the damping rates on-the-fly. Essentially, to improve comfort, the LX roll control is less (suspension more independent = more vehicle roll) under straight-ahead and light turning conditions, but roll control increases at higher turn rates/accelerations. Whether that actually translates into better overall roll control at higher lateral accelerations I don't know, but like I said, I don't see a significant overall difference in vehicle roll in my converted LX, and the (LX Stabilizer Bar + LC springs/tbars/shocks) combo does just fine in the vehicle roll control aspect in my opinion. I think part of that may be due to the stiffer spring rates (constant) with the LC hardware and the fact that those springs are effectively "decoupled" from one another under all conditions except for Stabilizer Bar influence.
Dont say that...i am going on 11 years this Spring 2011 and want to get my front bumper, winch and maybe a snorkel on before I have to rip out the AHC and put on Ironman Heavy...
SHERMAN FJ62
Charlestons' King of Cruisers
The new Land Cruiser's are nice but their suspension system I think is their only week point. To bad they wont sell us american's Land Cruisers like they sell the rest of the world.
Brock I think you need a good solid FJ60 or FJ62 simple rugged unique and industructible.
HE HE HE
Like the rear bumper it looks great, glad you found someone to help you, I have been out of state for a while
Brock I think you need a good solid FJ60 or FJ62 simple rugged unique and industructible.
HE HE HE
Like the rear bumper it looks great, glad you found someone to help you, I have been out of state for a while
uHu
Bridgeburner
That's a lot of words about a very small issue....
1
The Neutral Pressure check is described in other threads in here. (It's the only way of checking the state of your steel springs (and partly also the pump capacity) on an AHC equipped vehicle)
2
When the car is 10 years old, then of course the springs are weakened, That happens with all steel springs. This is not special for AHC, and has nothing to do with the AHC Service Life. Without AHC you would also need new springs after 10 years (not to mention shocks) - it's just that when you have the AHC you don't notice how weak the springs have become until the AHC is overpowered by gravity.
3
There could of course be some other problem with your suspension system, but what you describe is normal and expected from a 10 year old, so why not check the expected first, namely the state of your coils and TBs.
4
By replacing the AHC with regular suspension, you would have a standard LC100 setup, and I don't think it has any more of a roll-over problem than an LX, except if lifted.
1
The Neutral Pressure check is described in other threads in here. (It's the only way of checking the state of your steel springs (and partly also the pump capacity) on an AHC equipped vehicle)
2
When the car is 10 years old, then of course the springs are weakened, That happens with all steel springs. This is not special for AHC, and has nothing to do with the AHC Service Life. Without AHC you would also need new springs after 10 years (not to mention shocks) - it's just that when you have the AHC you don't notice how weak the springs have become until the AHC is overpowered by gravity.
3
There could of course be some other problem with your suspension system, but what you describe is normal and expected from a 10 year old, so why not check the expected first, namely the state of your coils and TBs.
4
By replacing the AHC with regular suspension, you would have a standard LC100 setup, and I don't think it has any more of a roll-over problem than an LX, except if lifted.
Tinkerer,
I am planning to do the same conversion on my LX as welll using LC stock parts. Can you help me answer a few questions:
1. Do I really need to replace the LX torsion bars with the LC's? I was thinking of keeping the current torsion bars and just replacing the shocks and coil springs.
2. Did you remove the existing AHC components or just keep them in place and cap off the lines?
thanks for any help.
You can remove them or just cap the lines. Face it, you're not gonna put it back in so why leave it there? Spend the extra time to remove the stuff.
Yes, you do need to replace the t-bars. AHC takes up some weight and the t-bars and springs the other. If you remove the AHC system, you wont have enough spring rate in the t-bars to hold the front up. If you dont think I'm right, then why are you replacing the springs in the back? Oh that's because those cant hold the weight EITHER.
Yes, you do need to replace the t-bars. AHC takes up some weight and the t-bars and springs the other. If you remove the AHC system, you wont have enough spring rate in the t-bars to hold the front up. If you dont think I'm right, then why are you replacing the springs in the back? Oh that's because those cant hold the weight EITHER.
1. Yes. You need to replace the torsion bars. The LC bars are larger diameter, designed to hold the load without assistance from AHC.
2. I left AHC components in place, other than the "Shocks". Yes, it is only time and work to remove them, but time is one thing I don't have enough of nowadays, and it does not hurt to leave them in place. I banded plastic bags over the ends of the hydraulic hose connections previously connected to the AHC "shocks", and positioned them where they would not interfere with anything.
