Hi From The Netherlands & AHC Issues (1 Viewer)

[YvesNL]

(Edit 9 October 2017, Problem found in post #44)

Hi All,

I’m Yves from the Netherlands, a 22 years old electronic engineer and I as most people on here I love Toyota Landcruisers. I found one I could afford, so a few weeks ago I purchased a Toyota Landcruiser 100.

The exact model on paper is a : “LANDCRUISER 100 4.2TD EXEC AUT SW” (with AHC). I know the system can be removed, but I drove a few AHC cruisers and actually like the system.

I have some fabrication skills (metal, wood & plastics), (CNC)machines & electronic skills. I'm planning on fixing, modifying and maintaining the cruiser myself.

It used to belong to a farmer and it is a very unloved model. It has been standing still outside for two years because he had bought a “new” 200 series. The car was very dirty and has some minor damage and scratches, but that is a concern for later.

According to the man I bought it from the AHC was fully functional when he put it away. When he charged up the batteries and started it again the rear end was lower than the front (front normal, rear low). I also noticed this when I saw the car for the first time. Here is a picture of the height difference:

Before I purchased the car I did a bit of searching on the internet and I found this beautiful forum. After an hour of browsing I was convinced that it would be the rear height sensor.

After I bought the truck and drove it home. With the rear as low as it could be this was quite a bumpy ride. But this was also the only technical thing that was wrong on the car that I knew of.

At home I took the rear height sensor off the vehicle and checked it with a 4.5v supply and a multimeter (like in FSM). The rear height sensor seems to work just fine. I bolted the sensor back to the vehicle and ordered a techstream adapter. (I'm also searching for a FSM with AHC).

Meanwhile I checked some things, started the car without the rear height sensor, without the pressure sensor (the one at the pump) and also lifted the rear again. At this point the front also lowered to the lowest position possible and never came back up again. see picture above & below.

If I power the pump from an 12v source, or short out the relay connectors, the pump runs. I have never heard the car switch the pump on by itself.

One thing I noticed is that the rear door lights never turned off. And for AHC to function all doors must be closed. It was the left rear door switch, the lights now went off, but the AHC still doesn’t work.

At this point I received my techstream (china) adapter cable and got techstream up and running. The first thing I did was connect my laptop to the vehicle, and started to lift the frond and back with the forklift. All height sensors give “normal” numbers throughout the whole range.

All the pressure sensors (Front, Rear & accumulator) are at 0,0 Mpa-g. If I try to run an active test the system gives a warning. Something like: “make sure all conditions are met and try again”. And all conditions were met.

There were two fault codes: C1713 “Rear Height Control RH Circuit Malfucntion” and C1718 “Pressure Sensor Circuit”. I believe these codes came from unplugging these devices and starting the vehicle after. After removing the codes from the system they never came back.

After all this I tried to do the “manual active test”. Next to the air filter I found the diagnostics connector. I connected TS & E1 with a jumper cable, pushed down on the AHC control switch five times within five seconds after starting the car and the “off” light was blinking in 0.25 second intervals. (the ABS was also blinking at this point). But no matter what buttons I pushed, the car did not raise, and the pump did not start.

I also checked the AHC Fuses, they are good. The relay also switches nicely (when applying 12v manually). If I take my multimeter to the switching side of the relay, I only measure 0.0v. The relay does not get switched on.

Is there anyone that could point me in the right direction of what to do next? Any help would be appreciated. And of course, I also try to help people on the forum and want to be part of the community.

 

[RayW]

Hello Yves. Nice to have you here.
I too had issues with my AHC not functioning and a rear sag. I went through all of the same steps as you. Checked connections, bought techstream, pulled fuses, checked voltage, got pissed off, etc. I spent hours and hours. Everything seemed to check out fine.

A Toyota tech told me the systems are, for the most part, bullet proof and very reliable. He said most issues are caused by the ride height sensors.

Keep in mind, I had very low rear sag and the front was very stiff. So this was puzzling.
My system had power.
All fuses were good.
Pump had fluid.
Pump would run.
No obvious damage anywhere.

I took a gamble and my plan was to begin replacing sensors one at a time since I couldn't find any other issue. Luckly for me I hit on the first try. When I replaced the passenger side front sensor, the system returned to its normal state and works properly now.

Since your 100 has been sitting so long, my bet it that you have some corrosion somewhere that is causing the issue...probably inside one of the sensors.

Good luck on finding the issue.

 

[mkivtdi]

Will follow this as i have similar symptoms, but in the front. Front low, rear high. No warning on the dash, no pump sound when hitting H or L, just blinking green...

 

[YvesNL]

Hello Yves. Nice to have you here.
I too had issues with my AHC not functioning and a rear sag. I went through all of the same steps as you. Checked connections, bought techstream, pulled fuses, checked voltage, got pissed off, etc. I spent hours and hours. Everything seemed to check out fine.

A Toyota tech told me the systems are, for the most part, bullet proof and very reliable. He said most issues are caused by the ride height sensors.

Keep in mind, I had very low rear sag and the front was very stiff. So this was puzzling.
My system had power.
All fuses were good.
Pump had fluid.
Pump would run.
No obvious damage anywhere.

I took a gamble and my plan was to begin replacing sensors one at a time since I couldn't find any other issue. Luckly for me I hit on the first try. When I replaced the passenger side front sensor, the system returned to its normal state and works properly now.

Since your 100 has been sitting so long, my bet it that you have some corrosion somewhere that is causing the issue...probably inside one of the sensors.

Good luck on finding the issue.

@RayW Were your techstream height readings on the "broken" sensor correct?
Also, did your pump run automatically, or did you applied manual power?

Will follow this as i have similar symptoms, but in the front. Front low, rear high. No warning on the dash, no pump sound when hitting H or L, just blinking green...

Same with me, blinking light (HI) but no errors.

Today I did some work on the Cruiser. I will post some pictures of my sensors and techstream(errors).

 

[Matserelli]

Ik wist neit dat deze in Nederland waren! Dat moet groote zijn naast alle kleine auto's!
Welkom bij de club. Blij om een andere Dutchy te zien. Als u hulp nodig hebt, ben ik altijd blij om te helpen!

 

[YvesNL]

Ik wist neit dat deze in Nederland waren! Dat moet groote zijn naast alle kleine auto's!
Welkom bij de club. Blij om een andere Dutchy te zien. Als u hulp nodig hebt, ben ik altijd blij om te helpen!

They are one of the biggest cars in the Netherlands. But that is the fun part and, thanks nice to find another Dutchy aswell.

Yesterday I pulled all the height sensors off the truck for inspection. Here is a picture of all the sensors opened up just after removing them from the truck:

Below is a picture of the rear height sensor:

The sensor and screws had a lot of corrosion on the outside, but was acutally very clean inside. Measurements were also good (I think), Somewhere from 0.6 KOhms to 3.2 KOhms (I believe).

Below is a picture of front height sensor 1:

This sensor did not have a lot of corrosion on the outside. The inside was also very clean. Measurements fron 0.6KOhms to 3.2KOhms.

Below is a picture of the front height sensor 2:

This sensor also did not have a lot of corrosion on the outside. Hovever, the inside was quite dirty.
After a quick clean it looked normal again. This sensor reads from obout 0.6 KOhms to about 4.2 KOhms.

I assumed the Cruiser uses the height sensors (aka "potentiometer") as a resistor devider. In this case there shouldn't be a problem with the "front height sensor 2". Or can it be?

I also measured the traces on the backplate like in the picture below:

On the rear sensor this was 4.21 KOhms
Front left sensor was: 3.75 KOhms
Front Right was 4.19 KOhms

 

[YvesNL]

Below is a picture of my techstream:

At first there were three trouble codes:
- C1711 Front Height Control Sensor RH Circuit Malfunction (Because I had driven the car for a few metres with the sensor off)
- C1712 Front Height Control Sensor LH Circuit Malfunction (Because I had driven the car for a few metres with the sensor off)
- C1718 Pressure Sensor Circuit
After clearing the codes C1718 reappeared.
After clearing the codes again no codes reappeared.

But this does give me something to look for. So I tried testing the front pressure sensor.
As you can see in my techstream photo the front pressure is 0.0 Mpa-g.

Since the front pressure sensor is located before the solenoid valve it should give different values when the pump is running.
Please correct me if I'm wrong on this.

So that's what I did. I took out the AHC pump relay and shorted it out with a wire. The pump now runs, but I do not see a change in the front pressure.

I also tried performing the active test by shorting out TS & E1. Pushed dows five times within five seconds of starting the car. Ran the pump manually. But again, nothing (no movement & nothing in techstream.

After this I got the AHC relay back in and tried the active test "main relay" in techstream. And I got this error again:

My next step will be to check the pressure sensor without the cables attached. Supply 5V (have to check that) and a GND and measure the output with and without the pump running.

Thanks for comments and reading so far.
If anyone has any ideas or suggestions it would be very much appreciated.

 

[PADDO]

Couple of observations:
The pump output pressure is not constantly displayed, one sensor (on the pump body) reads and monitors the pressures for the entire system. Pressures are populated into the ecu and displayed as a sequence when a height transition occurs. Just hooking up Techstream without completing a height transition displays 0.0.

Techstream is showing vehicle speed, are you parked or moving?

Stop Light Switch should be OFF if you don't have your foot on the brakes. Also foot on brake for more than 4 or 5 seconds puts the system into a movement inhibited state.

Your front and rear Step values should both be 8 if you're not moving, I've never seen 0 - they range from 1 -15 for your dynamic damping. Even if you are moving at 7 km/h at such a low speed I'd expect the Step values to be 6, 7 or 8 but not 0.

Check your AHC ecu is properly connected to the three harness'. Pull the 15 and 20A AHC fuses and see if that resets the ECU, I've encountered a weird fault that wouldn't rest until the ECU had its power removed. It's easy to get sucked into a confirmational bias situation chasing height sensors or imaginary pressure faults but I'd be looking at why your ECU seems to be outputting unexpected values.

 

[YvesNL]

Couple of observations:
The pump output pressure is not constantly displayed, one sensor (on the pump body) reads and monitors the pressures for the entire system. Pressures are populated into the ecu and displayed as a sequence when a height transition occurs. Just hooking up Techstream without completing a height transition displays 0.0.

Techstream is showing vehicle speed, are you parked or moving?

Stop Light Switch should be OFF if you don't have your foot on the brakes. Also foot on brake for more than 4 or 5 seconds puts the system into a movement inhibited state.

Your front and rear Step values should both be 8 if you're not moving, I've never seen 0 - they range from 1 -15 for your dynamic damping. Even if you are moving at 7 km/h at such a low speed I'd expect the Step values to be 6, 7 or 8 but not 0.

Check your AHC ecu is properly connected to the three harness'. Pull the 15 and 20A AHC fuses and see if that resets the ECU, I've encountered a weird fault that wouldn't rest until the ECU had its power removed. It's easy to get sucked into a confirmational bias situation chasing height sensors or imaginary pressure faults but I'd be looking at why your ECU seems to be outputting unexpected values.

Thanks for your reply @PADDO .

I now understand the pressure of 0.0 Mpa-g.

Sorry I was unclear. The picture you see is from a moving vehicle (But I was breaking and about to come to a standstill).
The picture below is from when I was standing still. The "Stop Light Switch" is now "off"

In this picture the Front & Rear Wheel Step is also 0 step.

This afternoon I will pull the fuses and check if the AHC ECU is properly connected to the wire harness and report back on here.

 

[PADDO]

Ok, moving, got it. Still expect to see 8s in your step values whilst stopped. It appears you're re on the bump stops from the height feedback but front heights of -94 and -77 have a very large delta. I suspect -77 is closer to a realistic bump stop height value. There is a maximum delta value between front sensors to a point where the system sees the delta as unreasonable and rejects it as a fault, you may reached/passed that point. I'd try and get the two values within 10mm. Stock height for the front is about 500mm (where a factory set up sensor will return 0.0mm) hub center to fender bottom so you can take some measurements and decide which is the more reasonable sensor result. Or use your forklift to get the desired 500mm front height and adjust both your sensor brackets to read 0.0 or as close to this as possible. For the rear you want it to read 0.0 at 520mm or thereabouts.

 

[YvesNL]

Correct, the vehicle is on its bump stops, sensor arms were off. Wire harness is connected correctly.

Yesterday I took some hydraulic Toyota to the Toyota and corrected the sensor arms (used a hydraulic jack in the rear).

They are all quite close now. I have pulled the 15 & 20A AHC fuses and reset the ECU (left them out for a few mins).
After powercycling the ECU the step values were still 0 & system won't operate.

After that I tried taking power off the whole car and disconnected both batteries (left them off for a few mins).
Step values still 0 & system won't operate.

I checked with techstream to see if all AHC buttons work, and they do.

What actuator controls the step values? Is there a feedback loop that could have damaged components/faulty wires?

Picture of the techstream values:

Note: took picture with door open.

What do these values mean, I have my ideas, but maybe someone can tell me the actual meaning.

Motor relay ? (AHC pump?)
Main relay expectation ?

 

[El Cid]

Yves,

Ik heb en vrouw von Nederlands, en twee kinder met Dutch naams. I was in Amsterdam last week.

First, are you an Ajax fan?

Second, if you were near Amsterdam, I'd have offered to help!

 

[RayW]

Wow. You have done quite a bit of hard work! I know everything seems to suggest the sensors are ok but my bet is still on a sensor. Once corroded, failed, dirty and/or opened up, they are just awful.
I wish I could help more but that's all I can offer. I know this is frustrating.

Best in finding the problem. The 100s are fantastic vehicles.

 

[YvesNL]

Yves,

Ik heb en vrouw von Nederlands, en twee kinder met Dutch naams. I was in Amsterdam last week.

First, are you an Ajax fan?

Second, if you were near Amsterdam, I'd have offered to help!

No problem, I'll pick you up in Amsterdam. Only a 35 minute drive ha.
Sorry, I was born in Utrecht, So I'll have to go with FC Utrecht and not Ajax.
But I do not really follow(am not a fan and do not watch) football/soccer so no problems.

Wow. You have done quite a bit of hard work! I know everything seems to suggest the sensors are ok but my bet is still on a sensor. Once corroded, failed, dirty and/or opened up, they are just awful.
I wish I could help more but that's all I can offer. I know this is frustrating.

Best in finding the problem. The 100s are fantastic vehicles.

I'm going to test some other things, maybe people will have some other suggestions and I'll check.
If it is not working out I might just order three new sensors and fit them to the Cruiser.

@PADDO How does the dampening work? Is there something thet I can check to make sure there isn't a problem in the dampening system.

My globes do have quite some rust on them (the whole bottom actually has quite some rust).
Could the globes somehow cause the 0 setp error?

 

[YvesNL]

I just checked some more things on my Cruiser.

I started with cleaning th AHC ECU contacts, reseating connectors.
It made no difference in stepvalues or anything.

I powercycled the ECU 2 times and it also didn't do anything noticable.

After that I checked the four solenoids under the car, next to the accumulator.
I figured out that top-middle was ground and applied 12v power to the other pins (in sequence).
I can hear all the four solenoids "click", so I assume they work correctly. You can see the unit in the picture below:

For what it's worth I'll also show you my "globes":

More rust than I've seen on the forum here. But I'll replace these if necessary when the AHC functions.

Another thing that I thought was strange is this:
When I had the car up on a lift (with the wheels off the ground) the AHC light moved to low.

I thought this was strange as techstream showed this data:

The picture below shows the Cruiser on the lift.

If anybody has a idea or suggestion of a solution, or knows something that I can try. I'd like to hear from you.

Don't know what the next step is yet, I hope to get some suggestions.

 

[YvesNL]

Just ordered three new height sensors. Just the sensors, not the linkages.
Amazon won't ship the sensors to the Netherlands so they will ship from Lithuania, I'll receive them in a few days.

In the meantime I can:
- Check the pressure sensor by hand;
- Find a FSM with AHC in it.

 

[hj 60]

The FSM is the first thing you need, it might have a valid test pattern.
Does the light change when you lower the car? and if you lift one wheel with a jack does the values change?
To me it is strange the diagnose system thinks nothing is wrong, that would (probably?) only happen if something in the first or last test signal sequence is wrong.
If one of the components is faulty the computer would give an error, yours does not give any error so I don't think one component is faulty, or the fault does not arrive at the computer> maybe the computer is defect?
What does the computer do if if does not get a response?

Have you read every topic about this on the internet because you cant be the only one.
Definitive list of AHC maintenance items

Why would the computer think the ahc is low while wheels are of the ground (that should be high if anything?) maybe one main or a few (rusty?, draadbreuk?) cables are giving a lot of interference or resistance?
maybe if you place a picture of techstream circle or mark the value you think is suspicious (for fast interpretation by others)

And the previous owner claims it was parked while working fine, so then a few years of no movement (so cables are not damaged) but (moisture/rust) ? and now errors.

what helps for broken wet phones is rice and oven, maybe the computer is rusted/wet?

Can you repeat the lift and lower with the jack and does the lights repeat because I would try to drive it more, get the engine warm and lift/lower a few times with jack and hope it catches up.

If you clean the parts with a toothbrush and wd40 it will be clean for the next years, I think the rust on the compressor must be removed, also to check the lines, no leaks?

 

[YvesNL]

Thanks for your comment, I'll address some things that I haven't told yet.

I have spent a lot of hours and read a lot of topics on different forums. I did find a lot of topics on the AHC and similar issues, almost always sensors or other "simple" faults. That's why I ordered the sensors, just to be sure.

The light now stays on "LO" even when the car is lowered on its wheels or when I lift only one side.
Even after driving it back & forwards and restarting the engine. Haven't pulled the AHC ECU fuses after this yet.

Last week I cleaned the contacts of the AHC ECU, with WD40 and a brush. It didn't do anything so far.

You're right, it is strange that the AHC system passes the initialisation of the ECU but doesn't function.
I've checked numerous connectors and contacts including: fuses, relay, height sensor connectors, pump connector, pressure sensor connector, 1x solenoid connector, 4x solenoid connector, and AHC ECU connector.

I contacted some people for a FSM. If I know how the cables run I can measure the resistance of them all and make sure they are allright and there is no broken wire (draadbreuk @hj 60 ).

About techstream. According to my knowledge the values look normal. But I don't know what all of them mean. As @PADDO pointed out the "step" values are off. They are located under & left in my techstream pictures Parameter: "Front Wheel Step" & "Rear Wheel Step". Both values are 0.

The computer does register a lot. If I disconnect the rear height sensor the ECU notices. Same goes for both front sensors and the presure sensor. So the AHC ECU is not completely broken.

I might just take the ECU out and do a visual inspection of the PCB. I've got a IR and Convection reflow oven, I can heat the board to 50 or 60 degrees celsius to get any moisture out or even do a full reflow if necessary.

I will keep you all updated.

 

[Wilsil]

Welkom op dit forum Yves. Another Dutchy here. located in Australia.

I didn't read if you checked the fluid level though.
Is that still in a good condition or did you change out the fluid?
By seeing only "0" values it almost looks like there is no connection somewhere, like a broken wire.

 

[YvesNL]

You're right, I should have told you that I have checked the fluid level.
There is enough fluid in the resevoir (Above max in "LO").

I think I'll have to check the connectors on the "dampeners", take off the protection covers and check those connectors for signs of corrosion.
Haven't done that yet.