Quick question about AHC ride with extra weight (2 Viewers)

[ParaJake]

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.

 

[IndroCruise]

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.

To elaborate on Height Control Sensors and their connectors and harnesses ....

A Height Control Sensor DTC only arises under the very specific fault conditions exactly as specified in the FSM extract attached to Post #88, and also attached to this Post.

A degraded Height Control Sensor easily can be transmitting a voltage within the FSM-specified voltage range for the Sensor but which is the wrong voltage for the height of the vehicle.

All it takes is some internal corrosion or internal wear which increases resistance, or some tracking (which may not be visible to the eye) which reduces resistance, or some other fault, and the resistance in the Sensor will be different to what it should be at a given position. If so, the voltage signal to the ECU will be different to what it should be at a given Sensor position.

For example, a degraded Sensor might show, say, 1.5 volts at mid-swing position (which is the correct "N" height position) instead of the expected 2.25 volts which is expected at this position.

The ECU has no idea and no way of knowing anything about the physical conditions inside the Sensor. All the ECU can do is pick up the voltage sent by the Sensor and detect whether it is within the range which the ECU is designed to accept, as defined in the FSM Diagnostics section, specifically: 0.3 volts to 4.7 volts

In this example of 1.5 volts at mid-swing, when "N" height setting is selected at the console switch, the ECU still will cause adjustment of the vehicle height until the point is found at which Sensor delivers the correct voltage (~2.25 volts) to the ECU, corresponding to "N" height as set in the ECU design.

If the Sensor is degraded, this voltage will be found at an incorrect position and not at the correct mid-swing position.

In this case, to achieve the voltage expected at the "N" setting, the vehicle will be moved to an incorrect height until the required 2.25 volt signal is transmitted by the Sensor and received by the ECU.

If the voltage is in the range that the ECU accepts, then there will be no DTC.

If the voltage signals from the three Height Control Sensors are widely different from one another and outside the tolerance of the ECU, then the ECU is unable to resolve the conflicting information. Even though different from one another, so long as each of the three voltage signals individually are within the acceptable range, there will be no DTC.

This also will show up on Techstream as widely different Height Control Sensor readings, instead of the required zero inches +/- 0.2 inches suggested in the FSM. (In reality, there may be a little more toletrance than this).

In such a case of large differences, the ECU will put the AHC system into 'fail safe' mode, whether or not there are DTC's. 'Fail safe' mode will remain until the conflicting signals are resolved the Owner or Mechanic.

This means that the ECU will attempt to put the vehicle into 'standard height', meaning "N" height, which really means that it will attempt to put the vehicle into a height which is as close as possible to 2.25 volt signals from all Sensors.

If the Sensors are degraded, this attempt will not be successful and will result in very different Front and Rear heights. (The Front AHC system is hydraulically interconnected Left to Right when the vehicle is stationary or steering is straight ahead. This equalises pressures, so the Front Left and Front Right must be raised equally -- in effect averaging the effects of the two Front Sensors).

This why I always recommend that the Height Control Sensors (and their connectors and harnesses) be checked out whenever

.. there are large differences in Sensor readings on Techstream (these are more easily seen than the corresponding actual voltage signals), or

.. when there is strange actual Height Control behaviour,

whether or not there are DTC's -- especially given the age of the Rear Height Control Sensor in this case.

 

[ParaJake]

Thanks @IndroCruise
I've attempted the active test with the bridged wire in the diagnostic port. The vehicle would not move.

I have connected the vehicle to TechStream and took the picture below. (Sorry about the bad picture quality. Old Windows computers really make taking camera screenshots a challenge.)

It seems that I may, in fact, have a problem with the rear height control sensor. The height control sensors are showing:
FR. -2.8
FL. +2.6
RR. -0.2

I'd also like to add that now with the Active Suspension relay in place, the +B Power Source Voltage is reading 12.7V so that's fixed.

I'm thinking I'll pick up a rear height control sensor now and see where that gets me.

EDIT: Now that I look at it, it doesn't look like the rear has lifted much at all. The truck looks like it's got a mild Carolina Squat going on....

 

[ParaJake]

Correction!: I'm an idiot.

Sorry for the rapid fire responses everyone, I'm posting as I make discoveries.

So I just realized I've been doing the active test wrong this whole time. On the procedure it says to use comfort mode. I didn't realize that meant the selector had to be all the way to the left. I had it in the position second from the left. The active test DOES move the vehicle as it should.

I have placed the vehicle height into the height that it is supposed to be at based on @suprarx7nut video and AHC cheat sheet.

I did notice that the HI/N/LO indicator on the dash did not change when the vehicle was raised or lowered. The Neutral indicator stayed solid after the vehicle stopped moving up or down. Even when the vehicle was raised and lowered to the limits.

 

[IndroCruise]

Correction!: I'm an idiot.

Sorry for the rapid fire responses everyone, I'm posting as I make discoveries.

So I just realized I've been doing the active test wrong this whole time. On the procedure it says to use comfort mode. I didn't realize that meant the selector had to be all the way to the left. I had it in the position second from the left. The active test DOES move the vehicle as it should.

I have placed the vehicle height into the height that it is supposed to be at based on @suprarx7nut video and AHC cheat sheet.

I did notice that the HI/N/LO indicator on the dash did not change when the vehicle was raised or lowered. The Neutral indicator stayed solid after the vehicle stopped moving up or down. Even when the vehicle was raised and lowered to the limits.

No -- you are not an idiot -- you are learning these AHC/TEMS systems the same way many of us did, certainly me – by hands-on personal experience!!

Yes – definitely use the video and “cheat sheet” provided by @suprarx7nut.

Just first check that Front cross-level (hub-to-fender by tape-measure) is still good – previously at your Post #21 the Front cross-level was fine. It does not matter what these measurements are at this point, they just need to be equal, with the engine OFF so that there is no possible interference from the AHC system (and because the FSM says so). Equalise with Torsion Bar adjusters if necessary, not Height Control Sensor adjusters.

When you have got the hub-to-fender ‘operating heights’ (also called ‘ride heights’) where you want them using the “Active Test” procedure, turn the engine OFF and remove the paperclip ‘bridge’.

Now it is time for one more go at re-setting the Height Control Sensors as close as possible to zero. To do this and setting out the steps which follow ….

• Hub-to-fender 'operating heights' remain unchanged, set using "Active Test" as described above,

• Techstream connected, with Height Sensor readings visible,

• Ignition ON but Engine OFF – don’t want any interference from the AHC system during this part of process,

• Jack-stands in protective positions below chassis rails if working under the vehicle,

• Use the slider adjusters to get all three Height Control Sensor readings as close as possible to zero – yes, you can ‘fine tune’ with heim bolts at the Front but suggest do that later, don’t sweat ultra-accuracy at this stage, just aim at getting the system to work properly,

• When done, start engine, select “HI” (or “LO”), wait until vehicle stops moving, then select “N”,

• This is the ‘moment of truth’! If all is well with the Sensors, when “N” is selected, the vehicle should return to the near-zero Height Control Sensor readings on Techstream AND the hub-to-fender measurements should return to the measurements at all four wheels, all as previously set at "N",

• A few iterations may be necessary to get this right, with a drive around the block in between efforts, so as to let the suspension settle in the newly adjusted positions – then check, measure, re-adjust if necessary,

• If all is NOT well with the Sensors, and it is impossible to achieve the desired Height Sensor readings on Techstream and the desired hub-to-fender measurements by tape measure, it is time to take off the Rear Sensor and test it per the FSM method, also dis-assemble, clean up and re-test. [I won’t hide my prejudice to replace this 15 years old Sensor anyway – for long term reliability – but that is your decision],

• When Sensors and ‘operating heights’ are sorted out and when the vehicle responds correctly to the “Raise” and “Lower” rocker switches on the console, it is time to check AHC pressures, and deal with any over-pressures you find – that can be a separate discussion (note that AHC pressures by themselves tell you nothing about the condition of the ‘globes’),

• Finally, when AHC pressures are correct, test the overall condition of the ‘globes’ by comparing the number of graduations at the AHC Tank at “HI” and “LO” heights: a difference of 14 graduations means the ‘globes’ are as new; a difference of 7 graduations means the ‘globes’ are due for replacement,

• When you feel the situation is under control, and given the AHC/TEMS systems had little maintenance by the previous Owner, it is time to focus on the possibility of unwanted air being in the system, and very importantly, time replace the AHC Fluid, [Fluid change timing may depend a bit on whether you decide 'globe' replacement is necessary -- but suggest don't leave the AHC Fluid replacement for too long -- ancient AHC Fluid leads to lots unwanted problems].

Best wishes for ongoing success with the restoration of your vehicle!!

 

[ramangain]

Ok, so the AHC pump/motor is confirmed working, again.

My rig is currently sitting on a trickle charger. You can borrow parts off my 01 LX for testing if you come to my house in Dayton and spend some time having my fresh set of eyes look at things with you.

 

[ParaJake]

@ramangain
I appreciate the hospitality! However, I believe I found the main problem!

I realized, based on my very limited electrical experience, that the height sensors are just potentiometers. Which are relatively low tech.

When I installed the new sensors I noted that the front right sensor was reading in reverse. To reverse a reading in a potentiometer, you just have to reverse the positive and negative terminals.

So, using alligator clips and wires, I reversed the red and black wires in the connectors and left the yellow wire in the same position.

I reconnected TechStream and turned the vehicle on and VOILA! The front right sensor is now reading as it should and the switch is operating as it should. Sensor readings need slight adjustment, particularly the rear. But, it works, nonetheless.

I figured, since the hood was up and I had easy access, I measured the graduations from LO to HI in the fluid reservoir. ≈10-11 graduations. So my globes are relatively good to go as well.

To be on the safe side, I ordered a new rear height control sensor because the old one is so seized up that I'm just spinning the bolt in the mini ball joint of the sensor trying to adjust it. The new one should be here next week sometime.

So I'll take the vehicle home (it's at my dad's shop right now) and cut and solder the wires from the sensor in reverse for red and black. That should solve the reverse reading from the FR height control sensor and, in turn, solve most of my issues.

Next step will be to bleed and replace the old fluid in the hydraulic system.

 

[ClassyJalopy]

@ramangain
I appreciate the hospitality! However, I believe I found the main problem!

I realized, based on my very limited electrical experience, that the height sensors are just potentiometers. Which are relatively low tech.

When I installed the new sensors I noted that the front right sensor was reading in reverse. To reverse a reading in a potentiometer, you just have to reverse the positive and negative terminals.

So, using alligator clips and wires, I reversed the red and black wires in the connectors and left the yellow wire in the same position.

I reconnected TechStream and turned the vehicle on and VOILA! The front right sensor is now reading as it should and the switch is operating as it should. Sensor readings need slight adjustment, particularly the rear. But, it works, nonetheless.

I figured, since the hood was up and I had easy access, I measured the graduations from LO to HI in the fluid reservoir. ≈10-11 graduations. So my globes are relatively good to go as well.

To be on the safe side, I ordered a new rear height control sensor because the old one is so seized up that I'm just spinning the bolt in the mini ball joint of the sensor trying to adjust it. The new one should be here next week sometime.

So I'll take the vehicle home (it's at my dad's shop right now) and cut and solder the wires from the sensor in reverse for red and black. That should solve the reverse reading from the FR height control sensor and, in turn, solve most of my issues.

Next step will be to bleed and replace the old fluid in the hydraulic system.

How in the world do the terminals get reversed inside a plug? In any case huge kudos for sticking with it and getting it worked out.

How is it doing over 6 months later?

 

[uHu]

That only means that his right sensor actually was a left sensor. The two are mirror images of each other.

 

[ParaJake]

Hi all, sorry for the constant delays. New house, new wife, and a baby on the way realigned my priorities.
I just wanted to post an update to this thread. The previous fixes all worked well and the AHC system was working fine for the most part. I was having an issue once in a while where the AHC OFF light would flash constantly as it did before. But, this only ever lasted for a few days at a time at most.

At the current time, however, all of these fixes were in vain! It was a sad day in early July. I was driving down the road, had a tire blowout and hit a large landscaping boulder at roughly 55mph. I got knocked out by the airbag and took the word of the people in the car behind me. They said I went airborne and the Land Cruiser dropped into a 4ft deep ditch. When I woke up, there were people helping me out of the car. I had no issues from the accident... other than my 100 series was totaled. I'll be damned if they didn't pull that car out of the ditch and it started up like nothing happened. Unfortunately it was belching oil out the bottom of the engine bay somewhere. I couldn't see where from. Insurance totaled the car out.

It's not all bad news though. When the insurance looked at the car and asked me about the accident and the car's info, they had their evaluator estimate the value of the car. It was a 2006 (16 years old) with 170,000 miles. I paid 14k for it. The insurance gave me $22,500 for it after the deductable! I was blown away! I used the money to buy a 2009 200 series.

As for the 100 series, I actually have a couple parts left over that I never got around to installing if anyone is interested.
I have a new rear AHC sensor. And a transmission pan filter and gasket kit. If anyone is interested PM me!

 

[uHu]

That's a sad ending for the car, but it saved you. RIP hero.
Congrats on the 200 - not quite a 100 series, but I guess it caters for you and your family just great.

 

[augustwest]

Reading through this thread for the first time was like binging a show on Netflix! Some great folks trying to help out. Also, what an ending! OP - glad you're OK and the insurance co did right by you.

 

[ParaJake]

Honestly, I'd rather have the car than the money. But I guess it wasn't as bad as it could have been!

 

[suprasvobodea]

I checked the Voltage going to the plug for the AHC motor and I'm getting no significant voltage. Specifically 0.064V

ParaJake

Im having the same problem after installing a NEW pump assy and filling the reservoir with fluid. I cleared the 1762 pump code and when I try to run the active test , it WILL NOT WORK! I have repeated this 6 times and it immediately shuts down and throws that dreaded 1762 code repeatedly. I ALSO measured the voltage to the pressure sensor on the pump and got 0.505V as well. So I purchased a NEW sensor, which also reads 0.602V ..almost the same. The TSM says its supposed to be 1.56-2-2 V or something like that. Since the Pressure sensor gives the wrong voltage, it is telling the ECU to shut down and not let it operate.
What do you suggest I do next? I am so puzzled , I don't know what to do anymore. My LX470 has not worked in 2 months!

 

[suprarx7nut]

ParaJake

Im having the same problem after installing a NEW pump assy and filling the reservoir with fluid. I cleared the 1762 pump code and when I try to run the active test , it WILL NOT WORK! I have repeated this 6 times and it immediately shuts down and throws that dreaded 1762 code repeatedly. I ALSO measured the voltage to the pressure sensor on the pump and got 0.505V as well. So I purchased a NEW sensor, which also reads 0.602V ..almost the same. The TSM says its supposed to be 1.56-2-2 V or something like that. Since the Pressure sensor gives the wrong voltage, it is telling the ECU to shut down and not let it operate.
What do you suggest I do next? I am so puzzled , I don't know what to do anymore. My LX470 has not worked in 2 months!

95% sure you have air in the line - probably right by the pump. Code 1762 pops up *VERY* quickly and turns off power (IE voltage) at the pump. That's how it's supposed to work. It's annoying, but that's how it's supposed to work.

I've dealt with this code a good bit myself with customer cars and I've helped lots of people through it on here. If you can't get active test to work, you can power the pump directly from the battery. The pump has nice big terminals right out in the open so it's not too bad to jumper it to battery voltage.

Ultimately, you need to move that air (or nitrogen) out of the lines through the bleeders and then figure out where that gas came from. Typically, it means the pump was run dry or there's a globe that is dead and releasing gas into the lines.

Forget the pressure sensor. Forget the voltage being sent to the pump. The ECU almost never fails and I've never seen anyone have a dead pressure sensor. I've seen many dozens with gas in the lines. it's always gas in the lines...