Quick question about AHC ride with extra weight (1 Viewer)

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Joined
Sep 24, 2020
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Location
NE. OHIO
Hey guys, I have a 2006 land cruiser and I like the ride on it for the most part but I feel I may be missing out on something due to having AHC problems. Everyone says the land cruisers ride like clouds, but its not all THAT smooth to me. It rides pretty good, but only slightly better than my 2003 stock 4runner that I traded for this 100 series.
My 100 won't drop to low or lift up to high. This isn't a huge issue to me if its not causing any deficit in the ride. But, I had never ridden in a land cruiser prior to buying this one and I have never ridden in any other land cruiser so I don't have anything to compare it to.

After starting my car and driving for a few seconds, the AHC OFF light flashes constantly. I had this checked by a Toyota dealership and they said it was all of the height sensors. Does this sound right? That ALL of the sensors are bad? Or is it a fluke?

I'd love to get this thing working 100%, but I can deal with non-working AHC for now.

My main question is about riding with passengers in the 2nd row seats. When I have passengers in the second row, the ride gets very bad and I feel bad for the people in the back. It feels like the suspension is bottoming out with no more than 500 lbs in the back seat. This can't be right as I know the towing capacity is way more than that and I know that this thing is rated for more than just a measly 500lbs of human flesh bags in the back. Its actually more like 400lbs. Could this rough ride be due to a failing AHC system? It doesn't ride bad with myself and another in the front seats.

Also, does the ride stiffness control knob (next to the AHC position button) work if the AHC height sensors are bad?

I'd like to mention also that my AHC height control has never worked since I bought this about 7 months ago.
 
Great pic. Very useful. Thanks @uHu. I haven't taken a look yet. I wonder, if it is disconnected, if that would throw a trouble code. And if it is disconnected, I wonder what benefits somebody would have by removing the relay. These pics at least give me a plug type to look for tucked under the dash.

EDIT: I did find the part on Amazon using the part number. It says temporarily out of stock. I wonder how "temporary" it will be out of stock.

This AHC Main Relay has not fallen out of the bracket. A previous Owner or Mechanic has been working here.

It is clear that @ParaJake did not remove the Relay. For the reasons explained below, it seems that the Relay was misplaced or has gone missing before @ParaJake acquired the vehicle 7 months ago.

The FSM advises that “the Relay is required to supply power source to the suspension control ECU. The relay comes ON a few seconds after the ignition switch is turned ON”.

The ‘Fail Safe’ Mode caused by AHC Main Relay failure (or presumably its absence) is quoted as follows (taken from FSM Page DI-248 and attachment to Post #94):

“If a trouble occurs in the AHC Main Relay circuit, the ECU prohibits height control and fixes the damping force at the sports mode”.

This ‘fail safe’ mode definition fits exactly with the description of symptoms given by @ParaJake in his Post #1 and subsequently:
  • No AHC raise/lower function,
  • No variation when switching from “COMFORT” through to “SPORT2”,
  • Not much damping, rough ride, especially with rear passengers on board,
  • The AHC has never worked since the vehicle was acquired 7 months ago.
So it seems highly likely that the absence or fault in the Relay is at least one of the reasons the AHC/TEMS system has not been working in the time that @ParaJake has had this vehicle. Sadly, the Toyota Dealer was unable to identify this problem.

The Part Number given in the example taken from the internet by @Rebus Knebus is 90987-02004 is available from Partsouq.com -- he advises that it seems likely to fits his vehicle.

For the Part Number given by @uHu taken from his 2004 HDJ100 is 89278-60010:

Partsouq.com (UAE-based) shows zero stock.
MEGAZIP (Singapore-based) show stock at USD57.39 plus shipping ex Japan.
Toyota USA shows availability at USD105.30 with free shipping -- see link:
8927860010 - Active Suspension Relay. Electrical, Make - Genuine Toyota Part - https://parts.toyota.com/p/Toyota__/Active-Suspension-Relay/63606210/8927860010.html

Hopefully the relevant connector can be found within the vehicle owned by @ParaJake . Even if the Relay is still attached, it is clear that it is not working and replacement is necessary with the appropriate Relay for the VIN

That may fix the problem on this vehicle – although I suspect that there will be more to do after a working AHC Main Relay is in place – but one thing at a time, best to wait and see.

The FSM-defined “DTC Detecting Conditions” are complicated and it is not yet clear (at least to me) whether or when a DTC would be recorded, given the voltages described by @ParaJake. Maybe this is getting a bit academic! The problem is pretty clear.

Actual IG Power Source Voltage around 12.7 volts while driving (12.3 volts in test at Post #13)
Actual +B Power Source Voltage around 1.5 volts while driving ( 3.0 volts in test at Post #13)


AHC Main Relay DTC Conditions.jpg
 
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Did a quick check and sure enough, the main relay is missing. I found the plug tucked up a little higher in the dash. I'm assuming this 4 prong yellow plug is where the relay should go?

16268823657366862565215664287200.jpg
 
@ParaJake yep, that looks like the correct connector.
 
@ParaJake yep, that looks like the correct connector.
That might explain why none of it is working. I did perform the manual active test with the paperclip in the DIAGNOSTIC plug under the hood. I was not getting any movement or noise from the motor/pump. Does this mean there are problems other than the missing relay?
 
Nothing will work without the relay. The power to the ahc pump motor goes through that relay. Directly from the 50 A ahc fuse, through the relay to the motor.
 
Did a quick check and sure enough, the main relay is missing. I found the plug tucked up a little higher in the dash. I'm assuming this 4 prong yellow plug is where the relay should go?

View attachment 2737403
I suspect we're staring at a previous owner's improper attempt to disable AHC. :facepalm:

Get that relay (tons of folks on the UZJ100 facebook group or here might have one remaining after they removed AHC) and then let's see what she does!
 
Maybe Slee has a spare from a previous AHC removal.

On that note, chances are high it is the same relay as on my 01. You're welcome to try mine for testing in Dayton. I haven't driven my truck in a month.
 
I appreciate all the help and resources. I have one on the way as we speak.

@ramangain I appreciate the offer. Im actually driving it down to VA to Virginia Beach tomorrow night for a week long vacation. If I was passing through the area, I'd stop and see if it works. The way I see it, I'll need one anyway, no matter what's wrong with the AHC. So I ordered one. I will be offline for about a week and the new relay will be here by the time I get back. So I will install it and let you all know the results when I get back.

Because I'm not sure if you all understand how the ride quality is, it doesn't feel sporty like it's in sport mode. Of course, I really don't know what sport mode feels like because I've never ridden in a Land Cruiser before. But I would imagine it's stiffer than the current ride. The ride now is actually very good. It rides better than my girlfriend's 2017 Corolla. Smoother anyway.

When I have riders in the back, its almost like the skocks aren't working like they should. Its very bouncy and it feels like it bottoms out easily. But, it's only myself and my girlfriend going down there so the ride will be great.
 
That might explain why none of it is working. I did perform the manual active test with the paperclip in the DIAGNOSTIC plug under the hood. I was not getting any movement or noise from the motor/pump. Does this mean there are problems other than the missing relay?

The AHC Main Relay is just a switch operated electrically by a solenoid – no switch, no power to the AHC system, so nothing works.

The fact that the relay has been removed says that a previous Owner or Mechanic was trying to fix a problem or disable the system. So, most likely other things will be discovered and a few DTC’s may come to light when AHC operation is restored after fitting a new AHC Main Relay. Suspect that the basic “things to do list” will include re-adjustment of Front Height Control Sensors and replacement of the Rear Sensor unless already done, adjustment of vehicle hub-to-fender heights, checking of AHC pressures and adjustments if needed, and consideration of replacement of ‘globes’ if and when needed.

None of this is cause for alarm. All of it can be handled on a do-it-yourself basis with insights from IH8MUD.

A 2006 Land Cruiser with AHC and only around 150,000 miles is a very good truck. I have one with around 130,000 miles (210,000 kilometres) although mine is a turbodiesel. Yours seems like a good vehicle and your pics show a reasonable underbody. Restoration of AHC/TEMS full functionality, comfort and longevity seems feasible and very worthwhile – certainly much, much cheaper than replacing the suspension with a conventional system.

You are learning about the AHC system on a learn-by-doing basis, as we all did! Thank you for sharing your experiences – it was another learning opportunity for me. Hope all goes well!!
 
Yep, all of the folks in the Cleveland area will now flock to you for help as the local AHC subject matter expert. Enjoy!
 
Hi all!
I'm back from my road trip and picked up the new relay on my way home. I figured, since it's so easy to install, I'd do it in a parking lot. Well, I can confirm that the AHC relay was a success in that I can control the AHC from the cockpit now. As soon as I pushed the HI mode, she sprung to life and lifted up pretty quickly......

Unfortunately, it's now stuck in HI.
When I pushed the button to go back to neutral position, the HI indicator stayed lit and the neutral indicator was flashing which, I believe, is how its supposed to show. But the system was not lowering the vehicle back to neutral. I tried turning the vehicle off and back on. No dice.

The HI indicator was still solidly lit and would not return to neutral and the vehicle would not drop down. I knew there was a speed override for the AHC so I decided to try to make the vehicle override the HI position by hitting the override speed which, if I remember correctly, is 15mph.

When I hit the correct speed, the AHC height indicators began flashing like the vehicle was dropping back down and the Neutral indicator stayed lit solidly. I thought that might have worked, but the vehicle is still physically in the HI position, but the vehicle thinks its in the Neutral position. I tried lowering the vehicle with the switch in the cabin, but it won't move. The indicator shows Neutral, vehicle is physically in HI, and when I push the down switch, the LO position indicator blinks but the vehicle doesn't move.

I did a quick search and saw a thread in which the responses said this may be a mechanical or electrical issue with the height control sensors.

I do like the way it looks rolling down the road in the HI position. But, it definitely rides much stiffer.

I'm glad I tested it in the HI position before testing the LO position first!

I have not yet connected the vehicle to TechStream to see if any DTCs are being thrown. There are no lights on the dash that aren't supposed to be on.
 
Hi all!
I'm back from my road trip and picked up the new relay on my way home. I figured, since it's so easy to install, I'd do it in a parking lot. Well, I can confirm that the AHC relay was a success in that I can control the AHC from the cockpit now. As soon as I pushed the HI mode, she sprung to life and lifted up pretty quickly......

Unfortunately, it's now stuck in HI.
When I pushed the button to go back to neutral position, the HI indicator stayed lit and the neutral indicator was flashing which, I believe, is how its supposed to show. But the system was not lowering the vehicle back to neutral. I tried turning the vehicle off and back on. No dice.

The HI indicator was still solidly lit and would not return to neutral and the vehicle would not drop down. I knew there was a speed override for the AHC so I decided to try to make the vehicle override the HI position by hitting the override speed which, if I remember correctly, is 15mph.

When I hit the correct speed, the AHC height indicators began flashing like the vehicle was dropping back down and the Neutral indicator stayed lit solidly. I thought that might have worked, but the vehicle is still physically in the HI position, but the vehicle thinks its in the Neutral position. I tried lowering the vehicle with the switch in the cabin, but it won't move. The indicator shows Neutral, vehicle is physically in HI, and when I push the down switch, the LO position indicator blinks but the vehicle doesn't move.

I did a quick search and saw a thread in which the responses said this may be a mechanical or electrical issue with the height control sensors.

I do like the way it looks rolling down the road in the HI position. But, it definitely rides much stiffer.

I'm glad I tested it in the HI position before testing the LO position first!

I have not yet connected the vehicle to TechStream to see if any DTCs are being thrown. There are no lights on the dash that aren't supposed to be on.

Congratulations on success so far!!

It is too late here to comment in detail but remembering the very large differences in previous Height Control Sensor readings, and given the current behaviour, suspicion falls on these Sensors and/or their adjustment.

Let's see what Techstream says. By the way, a faulty Sensor may or may not throw DTC.

I recall that the Front Sensors are new. Was the Rear Height Control Sensor replaced at the same time?
 
Congratulations on success so far!!

It is too late here to comment in detail but remembering the very large differences in previous Height Control Sensor readings, and given the current behaviour, suspicion falls on these Sensors and/or their adjustment.

Let's see what Techstream says. By the way, a faulty Sensor may or may not throw DTC.

I recall that the Front Sensors are new. Was the Rear Height Control Sensor replaced at the same time?
The rear height sensor is not new. It has not been replaced. I never bothered with it because it was showing good readings.
 
First time I've heard of AHC getting stuck in "H" almost all the cases I've heard of get stuck in "L" or "N"

It might sound dumb, but is there any evidence that someone spliced or played with the wiring at the AHC ECU? the photos you posted showed the empty bracket, but I couldn't really see the harness at the ECU to see if someone played with any of those wires. maybe I missed some other photos you posted.

The fact that the relay was removed is a clear indication that there was a known issue and that was the simple fix for someone else.
 
First time I've heard of AHC getting stuck in "H" almost all the cases I've heard of get stuck in "L" or "N"

It might sound dumb, but is there any evidence that someone spliced or played with the wiring at the AHC ECU? the photos you posted showed the empty bracket, but I couldn't really see the harness at the ECU to see if someone played with any of those wires. maybe I missed some other photos you posted.

The fact that the relay was removed is a clear indication that there was a known issue and that was the simple fix for someone else.
I can't see any obvious alteration in the wires or ECU. If there has been tampering, it was extremely cleanly done.

So, I let the car sit for a while in my driveway and when I started it back up, the indicator showed neutral but the vehicle was obviously in HI.

I selected the down button, at which point the vehicle was physically in HI but was showing Neutral at the indicator. The indicator showed LO selected and it was flashing. The front of the vehicle physically came down to the Neutral position, but the rear physically remained in HI. However, the indicator showed the vehicle was locked in Neutral.

To me, this sounds like an ECU issue or a sensor issue. I still haven't had a chance to connect to TechStream. I've been pretty busy just getting back home today. I'll have to do it tomorrow. I'm wondering if there is a disconnect somewhere with the rear height sensor. I never did do an actual check of all its connected components. I've only seen the readings in TechStream, which show within normal limits and visually it looks in good condition.
 
Will jumpering the right pins force the truck lower?
 
Not sure, never had to do it myself. It's the procedure Indrocruise posts
 
Not sure, never had to do it myself. It's the procedure Indrocruise posts
Then that would be the one. Connecting the correct terminals in the diagnostic port in the engine bay. This is the "manual" active test. I will try this tomorrow.
 
Then that would be the one. Connecting the correct terminals in the diagnostic port in the engine bay. This is the "manual" active test. I will try this tomorrow.

Yes "Active Test" per posts #41 and #74 in this thread.

However, I really think that the Rear Height Control Sensor needs to be come off for testing per FSM. See discussion and attachment at Post #88 in this thread.

As explained in Post #88 in this thread, a Height Sensor with problems does not always throw a DTC.

A DTC only arises under the very specific fault conditions specified in the FSM.

Absence of a DTC does not provide assurance that all is well.

Given its age, suggest be highly suspicious of the Rear Sensor.

If Techstream still shows you widely different Height Sensor readings, then there is a problem with either

.. Front cross-levelling of the vehicle (in your case 'front cross-level' was fine at your Post #21 in this thread, Right and Left hub-to-fender reported equal within one-eighth inch, better than FSM tolerance which is "equal within 10 millimetres or 0.39 inch"), so go to,
.. Sensor adjustment, or,
.. Degraded Sensor internals, or,
.. Damaged linkage, or,
.. Faulty connector, or,
.. Faulty harness.
 
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