LX570 AHC “Basics” - Added as sticky thread for AHC Issues (2 Viewers)

[ohlancaster]

Hello again, my astute pillars of the Lexus world. Can I impose an ongoing issue with the CA emissions and the ACH?
My '09 Lexus LX 570 Illinois Registration expired in January, and I am still dealing with the emissions/registration.
After replacing the Cats and taking the Christmas tree lights off, I decided to try L4 for the first time in four years. The lights came back on immediately upon returning to H4. Then, this sound started from the front driver's wheel well. It seems to go away if I'm accelerating. I believe it's related to the low gear, ACH, ABS, VCS...
My Lexus Dealer/Advisor said the tech didn't recognize the sound, which surprises me more because it's distinct.
My Car is in week three at the Dealer, and I'm frankly afraid to call to check on it.
Any thoughts? Thanks again for your help.
Any thoughts gents, ladies?
Respectfully Miguelito

p.s. I'm sure I accidentally annoyed the dealer when I offered some trails to explore...
The #1 Priority is the noise coming from the LF Wheel Well. I believe the noise's genesis comes from whatever triggered C1268.
1. Can they test the LF Wheel Speed Sensor with a multimeter? C0205
2. Then, test the L4 Switch Circuit. C1268
3. Then, go back and inspect the ABS Reluctor Ring/Tone Ring. C1236
4. Then, have them test the Brake Switch A/B. P0504 (Replaced 3 Years ago)
Thanks again for your help.

 

[lx200inAR]

Hello again, my astute pillars of the Lexus world. Can I impose an ongoing issue with the CA emissions and the ACH?
My '09 Lexus LX 570 Illinois Registration expired in January, and I am still dealing with the emissions/registration.
After replacing the Cats and taking the Christmas tree lights off, I decided to try L4 for the first time in four years. The lights came back on immediately upon returning to H4. Then, this sound started from the front driver's wheel well. It seems to go away if I'm accelerating. I believe it's related to the low gear, ACH, ABS, VCS...
My Lexus Dealer/Advisor said the tech didn't recognize the sound, which surprises me more because it's distinct.
My Car is in week three at the Dealer, and I'm frankly afraid to call to check on it.
Any thoughts? Thanks again for your help.
Any thoughts gents, ladies?
Respectfully Miguelito

p.s. I'm sure I accidentally annoyed the dealer when I offered some trails to explore...
The #1 Priority is the noise coming from the LF Wheel Well. I believe the noise's genesis comes from whatever triggered C1268.
1. Can they test the LF Wheel Speed Sensor with a multimeter? C0205
2. Then, test the L4 Switch Circuit. C1268
3. Then, go back and inspect the ABS Reluctor Ring/Tone Ring. C1236
4. Then, have them test the Brake Switch A/B. P0504 (Replaced 3 Years ago)
Thanks again for your help.

Might want to start your own thread. I do t see what your issue has to do with AHC (“active height control”).

 

[ohlancaster]

Might want to start your own thread. I do t see what your issue has to do with AHC (“automatic height control”).

Shoot, you're right. I apologlize.

 

[lx200inAR]

Maybe this question has been answered here previously, but does the "spring" force provided by the AHC change based on compression/extension of the shock?

In other words, as the shock compresses over a bump, does its force increase like a coil spring would as its compressed more? Can you assign a spring rate to it like you could a coil or leaf spring where it applies(for example) 250 in-lbs?

The compression increase comes from the globes. There is nothing to compress in the “shock” itself. You have the cool springs and the globes acting as springs being compressed.

 

[ohlancaster]

The compression increase comes from the globes. There is nothing to compress in the “shock” itself. You have the cool springs and the globes acting as springs being compressed.

Off subject, but for what it's worth, that sound was infact a bad bearing (2nd time to replace DF) that must not have been OEM.

 

[skrypj]

The compression increase comes from the globes. There is nothing to compress in the “shock” itself. You have the cool springs and the globes acting as springs being compressed.

Understand. But the shock is what is providing the force to the suspension. So is that force always the same regardless of where the shock is in its travel or does it increase as the shock compresses.

 

[ohlancaster]

Understand. But the shock is what is providing the force to the suspension. So is that force always the same regardless of where the shock is in its travel or does it increase as the shock compresses.

I had to re-read this three times. It increases as the Shock Compresses.

 

[TeCKis300]

Understand. But the shock is what is providing the force to the suspension. So is that force always the same regardless of where the shock is in its travel or does it increase as the shock compresses.

Two "springs" support the car. The coil spring looks to be a traditional linear rate winding. The hydro-pneumatic accumulator is the other spring. They are non-linear, but generally have a portion of travel that is somewhat linear, into a portion that is progressive and higher rate.

To your question, it's somewhat both, and tuned right could be the best of both worlds.

When unladen, the accumulator can work in its more linear rate region. To your question, yes the shock force increases linearly with travel. Not to be mixed with shock damping force which would stay somewhat the same as that's more dependent on flow volume than pressure.

In laden use, the accumulator could work in its more progressive and higher spring rate region. Which is perfect for better handling of high loads. I'm always impressed with how well the suspension rides and handles heavy payloads.

A common fallacy is that AHC high produces a harsher ride. I'm not sure that's true and I believe it's due to accumulators being worn having lost pneumatic volume causing it to prematurely work in a higher rate region.

 

[skrypj]

Two "springs" support the car. The coil spring looks to be a traditional linear rate winding. The hydro-pneumatic accumulator is the other spring. They are non-linear, but generally have a portion of travel that is somewhat linear, into a portion that is progressive and higher rate.

To your question, it's somewhat both, and tuned right could be the best of both worlds.

When unladen, the accumulator can work in its more linear rate region. To your question, yes the shock force increases linearly with travel. Not to be mixed with shock damping force which would stay somewhat the same as that's more dependent on flow volume than pressure.

In laden use, the accumulator could work in its more progressive and higher spring rate region. Which is perfect for better handling of high loads. I'm always impressed with how well the suspension rides and handles heavy payloads.

A common fallacy is that AHC high produces a harsher ride. I'm not sure that's true and I believe it's due to accumulators being worn having lost pneumatic volume causing it to prematurely work in a higher rate region.

I wonder if they mean that compressing the suspension to full squish becomes difficult. I put my truck up on basically 2 wheels(it was rocking between front left and right rear) last night in hi mode and my front right LCA was just barely kissing my PerryParts bump stop. It squishes it more when its sitting on flat ground in low mode im pretty sure

 

[slipkid13]

Might want to start your own thread. I do t see what your issue has to do with AHC (“automatic height control”).

AHC "Active Height Control" not automatic

 

[terrapin]

Help! I've got a C1713 code (Rear Height Control Sensor RH Circuit Malfunction) and I can't clear it through Techstream. I've replaced the sensor with a new Toyota part and the RR sensor still reads -10.7 inches. I can raise the entire rear via the Active Test Rear Wheel Up/Down, but can only lower it via Rear Height Solenoid. I'm a novice at Techstream and am afraid to try too much, but none of the up/down active tests did anything. Techstream says it's clearing the codes, but nothing changes.

I took a short drive around the neighborhood and it doesn't seem overly rough or bouncy. I've got the battery disconnected and will try it again in the morning.

 

[lx200inAR]

Help! I've got a C1713 code (Rear Height Control Sensor RH Circuit Malfunction) and I can't clear it through Techstream. I've replaced the sensor with a new Toyota part and the RR sensor still reads -10.7 inches. I can raise the entire rear via the Active Test Rear Wheel Up/Down, but can only lower it via Rear Height Solenoid. I'm a novice at Techstream and am afraid to try too much, but none of the up/down active tests did anything. Techstream says it's clearing the codes, but nothing changes.

I took a short drive around the neighborhood and it doesn't seem overly rough or bouncy. I've got the battery disconnected and will try it again in the morning.

View attachment 3638300

Most likely a wiring issue rather than sensor. Either that or the input on the ECU.

 

[grinchy]

I had a bum tech steam install that could see the sensors but not clear codes. Ended up being a driver issue for the canbus dongle.

 

[ROMR NTX]

A common fallacy is that AHC high produces a harsher ride. I'm not sure that's true and I believe it's due to accumulators being worn having lost pneumatic volume causing it to prematurely work in a higher rate region.

I suppose it depends on your definition of harsh. I have fresh globes and fluid. I would not call it harsh in H at all, but it definitely feels firmer to me. When I'm off road I much prefer to keep it in N until more clearance is actually needed.

It's possible this feeling is due to the higher ride height making side to side movement feel more dramatic.

 

[TeCKis300]

I suppose it depends on your definition of harsh. I have fresh globes and fluid. I would not call it harsh in H at all, but it definitely feels firmer to me. When I'm off road I much prefer to keep it in N until more clearance is actually needed.

It's possible this feeling is due to the higher ride height making side to side movement feel more dramatic.

I use high a lot off-road and it is as plush and flexy as N.

It's possible that it's the feeling of the suspension/shocks topping out in down travel that makes the ride seem harsher. Topping out makes the suspension feel stiff legged with more head toss. Which is one of the caveats of sensor lifts making AHC H less useful as it leaves little downtravel in that mode. This is where AHC Long Travel comes in.

Suspension Travel Comparison

Been meaning to do this to get some objective numbers to compare ride height versus droop travel versus compression travel. What better to do on a rainy day. Hope is that others may contribute and I'll update my table. We've known for awhile that some aftermarket suspensions increase what is...

forum.ih8mud.com

 

[ROMR NTX]

This is where AHC Long Travel comes in.

one day . . .

 

[skrypj]

I suppose it depends on your definition of harsh. I have fresh globes and fluid. I would not call it harsh in H at all, but it definitely feels firmer to me. When I'm off road I much prefer to keep it in N until more clearance is actually needed.

It's possible this feeling is due to the higher ride height making side to side movement feel more dramatic.

I agree with this. It feels more bouncy to me, but when you do run things over it doesnt feel like the suspension is any more resistant to flexiing to me. Mine are not new but my truck only has 50k miles so they are not old either.

 

[terrapin]

Most likely a wiring issue rather than sensor. Either that or the input on the ECU.

I definitely have a chewed wire on the right rear height sensor. I can see it with a mirror. It is at the far end of the cable, opposite of the sensor itself.

I can just barely reach it from where the spare tire goes, but its a struggle.

 

[LXCruza]

So, recently my AHC pump broke leaking all the fluid in one go, and my local Lexus dealer gave me a huge quote for the pump replacement. I decided to buy the pump assembly and AHC fluids off ebay and have my local mechanic replace it to save on costs, as I'm not handy with car repairs myself. My mechanic replaced the old pump with a new one, but now only the left (driver) side rises up. He can't figure out why the right side won't work. For context, when showed it to Lexus dealer originally, they said my rear right sensor was seized and they replaced it. Any ideas what might be wrong here? I really don't want to take it back to the dealer

 

[LX Cruiser]

So, recently my AHC pump broke leaking all the fluid in one go, and my local Lexus dealer gave me a huge quote for the pump replacement. I decided to buy the pump assembly and AHC fluids off ebay and have my local mechanic replace it to save on costs, as I'm not handy with car repairs myself. My mechanic replaced the old pump with a new one, but now only the left (driver) side rises up. He can't figure out why the right side won't work. For context, when showed it to Lexus dealer originally, they said my rear right sensor was seized and they replaced it. Any ideas what might be wrong here? I really don't want to take it back to the dealer

I would look into that sensor they replaced. Double check part numbers and installation. They screwed something up, is my guess