2013 LX570 with AHC failures (1 Viewer)

radman

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Will running new fluid through all 4 corners also get new fluid to the 5th accumulator?

I don't think so. I don't remember exactly what it's purpose is, but it is upstream of the corner globes.
When bleeding, the pump automatically refills the corners to return to N; however, the 5th only refills when you raise from N to Hi.
 
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I don't think so. I don't remember exactly what it's purpose is, but it is upstream of the corner globes.
When bleeding, the pump automatically refills the corners to return to N; however, the 5th only refills when you raise from N to Hi.
O. Is there a process for bleeding it? Raise to high and open bleeder until it stops coming out? I didnt do this when doing the fluid exchange. The old fluid was pretty nasty too.
 
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+1 for checking the sensor lift. I had an armature for one of my sensors seize and it caused all sorts of havoc for a bit. I would try bringing the front down 3/4 of an inch with the sensor bracket and see if that helps.

From the description of the problem, I'm with Lexzilla that it may be with the sensor or sensor adjustments. I'm thinking this as it dropped to L unpredictably.. I would bring the front sensors in particular down a bit and see if the system returns to normal operation and is able to get to high mode reliably.

I don't believe this to be a fluid bleed issue as you troubleshooted that a couple times. The system seems self bleeding to some degree as it cycles and will tolerate some amount of air. The FSM doesn't particularly call out bleeding of the center accumulator. I've done it to be thorough, but as the system cycles and goes into low, it will generally self bleed that component. The purpose of the center accumulator is to hold reserve high pressure fluid, so it can get into high mode quicker than just relying directly on the AHC pump.

Side comment, I'm with @radman in regards to the AHC system load capacity. It has huge headroom unlike the LX470 system. I just weighed my rig on a scale with trailer in tow, and I'm at 8,180 lbs for the tow vehicle axles (14,920lbs combined) and the system will lift into high on flat ground fine. On downhills where my heavy trailer bears more tongue weight on the LX, it will still lift, but will report "N" height as it finishes lifting. It's still at an elevated height, but not fully in "H", so the AHC system is indicating best effort ride height. So even at loads over what the system will support at constant heights, it won't just drop back to normal N, but an in between N to H.
 

radman

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same
O. Is there a process for bleeding it? Raise to high and open bleeder until it stops coming out? I didnt do this when doing the fluid exchange. The old fluid was pretty nasty too.

It has a bleeder, same as the others. As @TeCKis300 said, I should eventually flush itself, but I normally get that one before the corners.If I remember correctly, the rig won't drop when you bleed it. And it won't refill until you call for a raise.
 
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Thank you for all the advice, you guys rock. I ended up moving the front sensors down slightly about 1/4 of their travel. This along with another bleed on both front accumulators seems to have the AHC working a little better now - definitely more responsive. A preliminary test with 4LO has H setting maintained without dropping the truck back to normal height. As far as measurements H setting is now an inch higher than it had been previously and N setting remains the same. Next test will be going over some uneven terrain near the house in 4Lo and try to get it to fail (get stuck in Low height) like it did before. Fingers crossed!
 

grinchy

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Thank you for all the advice, you guys rock. I ended up moving the front sensors down slightly about 1/4 of their travel. This along with another bleed on both front accumulators seems to have the AHC working a little better now - definitely more responsive. A preliminary test with 4LO has H setting maintained without dropping the truck back to normal height. As far as measurements H setting is now an inch higher than it had been previously and N setting remains the same. Next test will be going over some uneven terrain near the house in 4Lo and try to get it to fail (get stuck in Low height) like it did before. Fingers crossed!
If you can sustain H in 4Lo than the terrain (aside from a wheel lift) won't matter. Glad that it's working again.
 

radman

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Thank you for all the advice, you guys rock. I ended up moving the front sensors down slightly about 1/4 of their travel. This along with another bleed on both front accumulators seems to have the AHC working a little better now - definitely more responsive. A preliminary test with 4LO has H setting maintained without dropping the truck back to normal height. As far as measurements H setting is now an inch higher than it had been previously and N setting remains the same. Next test will be going over some uneven terrain near the house in 4Lo and try to get it to fail (get stuck in Low height) like it did before. Fingers crossed!

I know you said you were having issues with techstream, but can you get in and take a screenshot of your AHC data list? I'm wondering if your offsets are way off, and you exaggerated things when you moved the brackets.

this screen:
 
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I know you said you were having issues with techstream, but can you get in and take a screenshot of your AHC data list? I'm wondering if your offsets are way off, and you exaggerated things when you moved the brackets.

this screen:

Alright, finally had the chance to wipe an old laptop and make it my "LX570 Terminal". Link below is to a real time split screen video of the Techstream AHC readout and the Drivers Front fender going from N to H height settings. Sorry for the shaky video...


I have videos of the other three corners too - the front passengers side pretty much mimics the driver's side. The rears shocks appear to be raising and lowering properly without dipping like the fronts. Rear height increase from N to H is 2.25-2.5"

I went to the dump today to weight the truck on their scale. 7120lbs with my 215lb self and 170lbs of dogs and 9 gallons of fuel (72lbs). I'd estimate a full overlanding loadout with: full tank (200lbs), my wife and son (180lbs), additional gear (100lbs), trailer (75lbs) - at least 7500lbs

I'd be fine with leaving the vehicle in N height all the time especially with the great approach angle we have with the new dissent bumper but the system automatically goes into H height when 4LO is engaged, and obviously we need 4LO

I'd like to get this truck working properly as we're planning to have it as our adventure vehicle for at least the next 5-7 years. I have a new OEM AHC pump and a pair of 79K front OEM shocks from Florida. The vehicle spent the beginning of its life on the sea coast of Maine so not exactly the best environment for the equipment.

Does my techstream data look similar to your readout? Thanks guys!
 
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radman

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So your front left (driver's side) starts at 34 7/8", goes up to to 36 3/4", but then settles down to 35 1/2"?


I haven't seen that behavior before. Your passenger side does the same thing?


but the system automatically goes into H height when 4LO is engaged, and obviously we need 4LO

You may have missed this, but 4lo does not automatically initiate Extra high mode... Extra high only occurs if you are in 4lo AND have a tire off the ground 'freewheeling'
 
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So your front left (driver's side) starts at 34 7/8", goes up to to 36 3/4", but then settles down to 35 1/2"?


I haven't seen that behavior before. Your passenger side does the same thing?




You may have missed this, but 4lo does not automatically initiate Extra high mode... Extra high only occurs if you are in 4lo AND have a tire off the ground 'freewheeling'

Correct, Passenger side does the same thing. I just confirmed that H height does not activate when 4LO is engaged thanks. Also, just purchased some front spacers. Is there anything on the Techstream data to indicate the front shocks aren't holding pressure because that's what it appears is happening
 

radman

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I didn't have time to look at the video earlier, but now that I have, It looks like it didn't update.
maybe I stopped the video too soon. Here's a picture of the after values:

F637683C-6C39-49A0-8F60-80DD7EC52DB3.jpeg
 
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radman

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so the only interesting thing i see is that your FR and FL Height control sensors are about .5 apart. That could be causing issues with all the other calculations.

Are you on level ground?
Where do you have the physical sensor nuts set?
My guess would be bad sensor or accumulator before changing out the pump.

Here's what I would do:
1) get on level ground
2) loosen the nuts with the rig off, then hand tighten them back up. (This will allow you to loosen them again by hand with the rig on)
3) start the rig, then slowly loosen and move the front right so it's closer to FL. (looks like your Passenger is .5 low). Moving the sensor nuts with the rig running (and doors closed) is no different than the suspension moving while driving.
4) once the sensor values are closer, try to raise to Hi again and see if it stays up.
 
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so the only interesting thing i see is that your FR and FL Height control sensors are about .5 apart. That could be causing issues with all the other calculations.

Are you on level ground?
Where do you have the physical sensor nuts set?
My guess would be bad sensor or accumulator before changing out the pump.

Here's what I would do:
1) get on level ground
2) loosen the nuts with the rig off, then hand tighten them back up. (This will allow you to loosen them again by hand with the rig on)
3) start the rig, then slowly loosen and move the front right so it's closer to FL. (looks like your Passenger is .5 low). Moving the sensor nuts with the rig running (and doors closed) is no different than the suspension moving while driving.
4) once the sensor values are closer, try to raise to Hi again and see if it stays up.

I got the truck on level ground and the front sensors were within 0.1" of each other. The video I took before was in my driveway which I though was level but is obviously not. Regardless, I tried raising the truck up again to H from N and it sunk back down. I ended up adjusting my sensor position to highest setting up front and lowest setting in back. It looks much more even now in N. I have a customer who is the GM of a Lexus dealership. He's going to show the split screen video to a tech who is familiar with AHC and see if he's seen the sinking before on other LX's (not holding my breath). I'll update this thread as I find out more. Thanks for your help Radman - If you ever find yourself in Northern New England LMK and we'll show you some cool spots!
 

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