Time for AHC removal - advice? (1 Viewer)

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Joined
Oct 1, 2016
Threads
5
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73
Location
Seattle, WA
Hey all,

Just bought a 2007 LX470 a few weeks ago. Everything is great except the harsh, bouncy ride. I knew before buying that I would have problems with the AHC. I'm thinking that I should replace it soon before it totally blows out and leaves me driving home for 3 hours on the bump stops. I would like something close to the stock land cruiser feel, so I'm thinking about going with OEM springs, shocks, and swaybars.

This repair looks reasonable, but a bit beyond my comfort zone. I'm in the Seattle area, so I was thinking about letting Torfab in Everett, WA do the work. Unless someone here wants to talk me into it a DIY :) So far, I haven't found any comprehensive guides about what to do. I have a vague picture of what to do, looks like:
  • Drain all the AHC fluid from the accumulators
  • Remove accumulators
  • Remove shocks and springs in rear
  • Replace shocks and springs in rear with OEM LC
  • Replace front shocks and torsion bars with OEM LC
  • Adjust the new torsion bar to level the height
  • Remove some fuses, maybe disconnect the AHC ECU, possibly disassemble the dash and black-out the blinking "OFF" light
I haven't done many complicated repairs. Things like diff oil, ATF flush and refill, intake gasket, throttle body cleaning, serpentine belt. Has anyone written up a comprehensive DIY guide for AHC removal? I'm seeing things about needing to cut through the body to access bolts on the top of the shock (this thread) and getting somewhat intimidated. Which steps am I missing, and what others parts should I replace "while I'm in there"? Rubber isolation ring? Maybe bushings? Do I need to take it in for an alignment afterwards?

Forgive my inexperience. I've already learned a ton from this website. Many thanks to the countless threads that go into far more detail than the factory service manual :wrench:
 
Hey all,

Just bought a 2007 LX470 a few weeks ago. Everything is great except the harsh, bouncy ride. I knew before buying that I would have problems with the AHC. I'm thinking that I should replace it soon before it totally blows out and leaves me driving home for 3 hours on the bump stops. I would like something close to the stock land cruiser feel, so I'm thinking about going with OEM springs, shocks, and swaybars.

This repair looks reasonable, but a bit beyond my comfort zone. I'm in the Seattle area, so I was thinking about letting Torfab in Everett, WA do the work. Unless someone here wants to talk me into it a DIY :) So far, I haven't found any comprehensive guides about what to do. I have a vague picture of what to do, looks like:
  • Drain all the AHC fluid from the accumulators
  • Remove accumulators
  • Remove shocks and springs in rear
  • Replace shocks and springs in rear with OEM LC
  • Replace front shocks and torsion bars with OEM LC
  • Adjust the new torsion bar to level the height
  • Remove some fuses, maybe disconnect the AHC ECU, possibly disassemble the dash and black-out the blinking "OFF" light
I haven't done many complicated repairs. Things like diff oil, ATF flush and refill, intake gasket, throttle body cleaning, serpentine belt. Has anyone written up a comprehensive DIY guide for AHC removal? I'm seeing things about needing to cut through the body to access bolts on the top of the shock (this thread) and getting somewhat intimidated. Which steps am I missing, and what others parts should I replace "while I'm in there"? Rubber isolation ring? Maybe bushings? Do I need to take it in for an alignment afterwards?

Forgive my inexperience. I've already learned a ton from this website. Many thanks to the countless threads that go into far more detail than the factory service manual :wrench:
DO NOT BREAK OPEN THE DASH TO FIX LIGHTS
DO NOT CUT THE BODY OF THE VEHICLE.

I mean it is your ride so do what you want. When I bought my 06 it was a harsh bouncy ride. But I had always planned on removing the ahc system. The ride now is better than stock. And it wheels great with a lil tire rub.
This is a big job but if you barrow or buy the manuals I can scan you pages. And just chip away at it. It took my a week everyday after work. I don't know how to post links whilst using my phone. But I tried to document the process.
 
This.

But if you decide to take out the AHC, I'd look at ICON.

120k miles on the LX470 currently. Fluid level is about 1cm below the min mark with AHC set to N. Going to do Paddo's single can flush when I get a chance. Then I'll do the height test and report back. Are you talking about the Icon performance series or VS 2.5 series? I don't do a ton of serious offroading, but I do sometimes drive around with 7 adults onboard.
 
Slee did mine and did a fabulous job. They put on an OME 1.5" medium lift with diff drop. I replaced the OME shocks that came with the lift with stock LandCruiser shocks soooo much better, but I don't have heavy bumpers or a winch. I think the OME's would've been fine if I did.
 
Hi All,

I did the height test and I'm getting 11 marks between low and high. From what I understand, anything above 7 is okay. Despite this, the ride is very stiff and harsh, and I've had passengers complain about it. I tried Paddo's single can AHC flush, and this didn't change the ride in any noticeable way. My plan now is to swap in stock Land Cruiser torsion bars, springs, and shocks. I'm planning on going to Torfab in Everett, WA for this. Should I ask the shop to save my used AHC parts? I assume that atleast the pump assembly and computer module are still good, and I can probably sell them on ebay.
 
Market for accumulators if you can get them pressure tested.
 
An 07 at 120k.... theres no reason why the AHC and AVS shouldn't still be perfect. If you have 11 marks between low and high and the AHC is functioning correctly, it's probably just fine and healthy. Something with the Adaptive Variable Suspension is probably wonky. Does moving the AVS switch make any difference in ride quality?

There's countless earlier LX's with at least double the miles that have had no issues with AHC/AVS. It's a fantastic and damn durable suspension system. Before tearing it all out, have somebody who is familliar with AHC systems diagnose whats going on. Could be as easy and cheap as a faulty switch leaving the AVS in Sport 2 mode all the time. Sport 2 is surprisingly firm for a big luxury SUV.
 
Mine has done 265,000 kms (165,000 miles) and still has the AHC.
 
Mine has done 265,000 kms (165,000 miles) and still has the AHC.
Hi Wilsil, just wondering do you mainly use the LC for dd/traveling, no off road? Where I'm, the road conditions aren't that good. Lots of uneven roads ( damage by overload trucks) and some holes. Would that shorten the life of AHC? Thanks for the help.
 
An 07 at 120k.... theres no reason why the AHC and AVS shouldn't still be perfect. If you have 11 marks between low and high and the AHC is functioning correctly, it's probably just fine and healthy. Something with the Adaptive Variable Suspension is probably wonky. Does moving the AVS switch make any difference in ride quality?

There's countless earlier LX's with at least double the miles that have had no issues with AHC/AVS. It's a fantastic and damn durable suspension system. Before tearing it all out, have somebody who is familliar with AHC systems diagnose whats going on. Could be as easy and cheap as a faulty switch leaving the AVS in Sport 2 mode all the time. Sport 2 is surprisingly firm for a big luxury SUV.

Thanks for the reply Andrew. If it's an easy fix, then I would definitely like to keep AHC for a few more years. The AVS switch doesn't affect the ride quality at all. I thought this was an indication that the dampener bladders were ruptured, or that they had lost enough gas to be ineffective. Maybe this isn't the case. AHC raises and lowers the vehicle just fine.

Is my next step to bite the bullet, buy a mini-VCI, and put windows XP 32 bit on my laptop and prepare for a weekend of AVS troubleshooting? :banana:
 
There's a saying in the Test Engineering world along the lines of "one or two valid tests are worth a thousand guesses". Essentially you need to be able to easily check signals and read neutral pressures to maintain the system; you need Techstream.
However there are several good tests that can be completed manually: check DTCs; damping system signal input test (for switches and other ECU inputs), and the 16 step damper actuator test (for ECU output).
You've really got to know what your pressures are and without the ability to read then (safe bet they are high to very high) you're going to strugggle to restore your system.
 
Seems crazy to me to swap out the entire suspension without putting the current one through an exhaustive inspection first. Especially on a late model low mileage 100. And swapping out globes isn't as expensive as everyone seems to think, if that's what it comes to. Cheaper than a full suspension swap.
 
Hi Wilsil, just wondering do you mainly use the LC for dd/traveling, no off road? Where I'm, the road conditions aren't that good. Lots of uneven roads ( damage by overload trucks) and some holes. Would that shorten the life of AHC? Thanks for the help.

My LX is mainly used for offroading with our 4WDclub. See my avatar for a flavour of what we do.
 
Update: ran a few tests tonight

My first step was to jump pins E1 and TC of the DLC1 connector (under the hood, behind the air cleaner, marked "diagnosis") to see if I can read any trouble codes related to AHC. The AHC was blinking at a constant rate, which indicates no failure codes were present (please correct me if I missed something in the procedure, I can't find the FSM online)

I tried the 16 step test next. I jumped pins E1 and TS on the DLC1 together, then started the engine. I assume I was in step 1 at this point. I went to all 4 wheels and pushed down. Super pillowy suspension, felt like a cadillac. Stepped through by pressing the brake pedal and observed as the stiffness gradually increased. By step 16 the suspension was very stiff.

This is frustrating, because it seems like AVS is working during the 16 step test, but not during normal driving. After this, I removed the jumper wires from the DLC1 and started the engine again. I set the dial to full comfort, checked the stiffness, then full sport, and checked the stiffness again, and there was no discernible difference :bang: Could this all be due to a 25 cent switch gone bad? Any recommendations for how to narrow down this issue? I'm considering commuting to work in diagnostic E1 + TS mode since this seemed to solve my problem. Just have to make sure I never press the brake pedal:banana:
 
You need to get techstream and diagnose through that. Honestly your pressures could just be way off causing a bad ride. My system was awful til I tweaked it to my liking.
 
When stationary the systems damping doesn't change from step 8s regardless of the switch position, unless you're in test mode. To check the comfort switch is working correctly you need to do the signal input test or monitor its status through Techstream where it's labelled SW1 and SW2. Above 3 mph it stays in your selected damping position regardless of pushing the brake whilst it test mode.
Has anyone mentioned yet that you need to know what your pressures are and get them back down to optimal?
 
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