Hi From The Netherlands & AHC Issues (1 Viewer)

[uHu]

It's time to locate the ahc ecu and check the connections to the different actuators. With the amount of corrosion under there, it wouldn't be surprising to find a missing connection.
Another piece of advice is that trouble codes and symptoms are not always logical on the ahc system. Because of a faulty rear sensor, I've had 1: front at max height, 2: front on bump stops, 3: a number of different codes that all disappeared with a new sensor, just as an example.
What is the production month of your cruiser? The FSM pages differ a bit over the years. And also the Active Test, iirc.

 

[YvesNL]

I've located and taken out the AHC ECU. The PCB looks very clean, no signs of damage or corrosion at all.

Here is a picture of the PCB:

Microscope closeup of fine pitch pins:

Microscope closeup of some diodes:

Microscope closeup of some mosfets:

As you can see, PCB is in good condition. No signs of moisture at all.
Soldermask is ok, solder is ok, waterproofing is ok.

I might just plug it in and watch it with the thermal camera to easily spot broken components if any.

@uHu thanks for posting. I've read some posts of you before about the different codes and symptoms.
I am going to check the connections on the "globes" next and have also acuired an FSM on DVD, it will be sent to me.

 

[wildsmith]

Isn't there an AHC rear harness fault that can develop on some models / years ? I've never experienced it but I'm sure I've read about it a few times on forums.

You're probably not as stupid as me but I once killed an AHC pressure sensor by trying to test it with jumper wires while it was still on the truck and accidentally touched two wires together and there wasn't even any magic smoke but the sensor never worked again! I didn't have Techstream at that time so don't know if it gave error codes but you'd think it would.

 

[YvesNL]

The first time my LandCruiser was registered in the Netherlands was on 7 Januari 2003.

So it is from January 2003 or slightly before, Transport etc.

It is the four speed and standard black grille. So I believe it is known here as 2000+ model and pre 2003.

 

[Wilsil]

Any luck Yves?

 

[YvesNL]

No luck yet.

I have put the AHC ECU back in, tested the system again. Techstream values (step) didn't change.

Have sprayed the bolts of "globe" connector caps for two days to get them loose.
Today or tomorrow I'll check those.

I received three new heigth sensors, just the sensors not the linkages.
Will be replacing these in the following days aswell.

Also received my FSM, so I'll have some reading to do.

I will keep you updated.

 

[YvesNL]

Today I checked all connector on the damping units. The connectors were under a load of mud.
Suprisingly clean on the inside though. Cleaned everything and reconnected.

I also coupled my new height sensors onto the connectors. I didn't installed the linkages yet as I derusted & painted (still wet) these.

Step values still 0 in techstream, car on lift, wheels off, car off ground.

Will put it on the ground tomorrow and test the functionality.

 

[YvesNL]

Yesterday I fitted the new sensors to the linkages.
FIrst I removed the rust, then painted a layer of rust protection, then two layers of matte black paint:

Fitted the sensors to the car, got it on the ground, has not solved the problem as expected. But at least I'll have new sensors so we know those parts are ok.

Next step is to check the four dampeners/actuators. In the FSM (and online) I found the "Damping force controlling condition check". Page DI-213 in my service manual.

I'll have to:
A - Short out Ts to CG in DLC3;
B - Start the engine. The damping force control actuator position becomes 1 position (it is 0 on front & rear right now);
C - Press & depress the brake pedal to change this value to 2, 3, 4, ..., 16.

I can use techstream to monitor the values and see if the system is working.

If yes, Nice!

If no (what I expect) I know I'll have to look at the wiring from the ECU to the four damping force control actuators & the actuators themselves. Like @uHu mentioned.

 

[YvesNL]

Two days ago I did quite some measurements and checked a lot of components. I printed out the AHC part of my FSM and started work on page one.

After every measurement I wrote the value Ohms/Pass/Fail in the FSM and went through the pages. I will post my progress and page numbers as it could help others.


First thing, check DTC’s: None.


After that I wanted to perform the “INPUT SIGNAL CHECK”. I hooked up techstream, selected the input signal check and got an error: 0x91020324 “It’s possible the requested function will work if you try again. If the problem persists please submit an error using the F12 key”

So… that didn’t work.

After that I just performed the check myself. Open up the data list in techstream and checked the signals listed in the FSM (on DI-211):

All inputs were correct, and according to the table they were good. But there was a thing that was strange.

When my wheels were straight the steering angle sensor in techstream does not give 0.0 degrees but -492.75. Also when I turned to the right techstream stated 153 degrees, fully to the left was -1145.40 degrees.

I do not have or had a trouble code that included the steering sensor. But I decided to look at the DTC 1781/81 page in the FSM (on page DI-265).

There the steering angle sensor is described as a incremental encoder

Then I checked the inspection procedure on page DI-267:

When I use techstream the value changes. But when I measures SS1 and SS2 with my multimeter I got different values. On both terminals I got values of 0.33v or 10.54v, obviously not good.

So we move on to page DI-268:

There was a voltage of 12.18v on pin 1 & 2, so this is a pass and we move on to step 3.

I did not apply separate power to the connector as described, but used the plug where the power of 12.18v was present. The resistance I measured was 3.7 to 3.9MOhms and was not changing from 0 to infinite. So according to the FSM I’ll have to replace the steering angle sensor.

Is there a way that this error would cause my AHC problems and prevent the system from being active?

Like the system not functioning, no DTC’s, no running pump, no warning lights, giving step values of 0?

After this I went on with checking the separate parts of the AHC system to make sure there are no other broken parts.

We move on to the height control sensor circuit. I just replaced all height sensors and gave the linkages a fresh coat of paint after stripping the rust. I adjusted the linkages and the values that I get in techstream are correct and change accordingly. I’ll see this as a PASS.

To check the fluid pressure sensor I measured PACC (pin 4 of connector s8 on the AHC ecu). First I measured in idle state, the voltage was 0.49v. Then I started the pump by jumping the relay, when the pump got pressure I measured 4.19v. I’ll see that as a PASS.

Time to check the temperature sensor. I measured ”TOIL” (pin 3 of S8), Voltage 2.16v, that is a PASS. Max 2.4v at 20 degrees C in FSM (page DI-218 for the pinout of the ECU and DI-233 for the temperature sensor).

Now it’s time for the interesting stuff. The damping force control actuators. First of all I checked the connectors again. All connectors are nice and clean and not damaged. After that I measured the coils of the stepper motors inside. I measured as in the picture below (FSM page DI-238).

All coils on ALL motors were 12.6 Ohms, so a PASS.

Next it is time to check the cabling to and from the actuators. You can find the schematic on page DI-237 of the FSM. All cables going to and coming from the ecu to the actuators measured 0.8 of 0.9 ohms. No open or shorted connections. So all the cabling to and from the actuators is good.

I did the same thing for the control valve assembly. You can find info on this unit on page DI-239 of the FSM. The pinout of the solenoid assembly is on page DI-242 of the FSM. All coils measured 3.6 Ohms. While I was in there I also checked the solenoid on the accumulator (big single thing, not to be confused with the four damping force control actuators. This coil also was 3.6 ohms.

I also applied 12v power to all the 5 coils (valve body 4x and accumulator 1x) and they all click nicely.

All cables between the solenoids and ecu are good. They all measure 0.7, 0.8 ohms.

Next to the AHC motor relay circuit. More info on page DI-243 of the FSM. The relay itself clicks, engages and disengages and is ok. The wire running from the ECU to the relay to switch the relay measured 1.4 Ohms. And there was 12.18v on the switched contact (one side offcourse).

Same thing with the main relay. Relay works, clicks and has continuity. All cables from and to the main relay seem to be ok.

I did not have time to check more. But all the parts until now seem to be OK. EXCEPT the steering angle sensor. That gives strange values. Could it be that the ECU probibits the function of AHC because of a faulty steering angle sensor?

I’ll be sourcing this part. Maybe first prepare more checks on it or take it apart.

 

[hj 60]

You are now a ahc specialist and still no fix, bummer but it must work out.
Does the ahc works in corners because it would be stupid if in the (eland test) corner test the ahc lifts the car and makes it roll over.
So I would think there is a complete stop switch in the steering wheel but is it mentioned anywere?
Maybe a sticker next to the button mentioning to only using it when driving straight?

The AHC system is integrated with the Stability Control System to reduce the body roll and sway.
from: site.activesuspensionsystems.com Blog / FAQ: Lexus LX470 and Toyota Landcruiser 100 accumulators.


you can remove the fuze from lower left kick panel...but when you do that (at least in the 2000 LX470) it also removes your steering angle sensor which is needed for VSC to function properly. I put it back in and my light flashes.
from: How to disable AHC dash light?

 

[YvesNL]

I read in a post from @uHu:

"With steering angle over 30 (or was it 35) degrees (and not standing still), the hydraulic connections between left and right shocks are blocked, in order to reduce roll when cornering."


And from FSM:

"And when it is judged that the steering wheel’s turning angle is large and the speed is greater than a set
value, the ECU causes the damping force to increase."

So Yes, the AHC system and the steering angle sensor are used to reduce bodyroll and pass a test like the moose test (eland test).

With a lot of faults in the FSM there is a line saying that this fault will prohibit the AHC from functioning. But not (that I can find) with the steering angle sensor.

 

[hj 60]

So did you remove the whole ahc system?

 

[YvesNL]

So did you remove the whole ahc system?

Almost, thought about it ha.

Still having problems, and no new steering angle sensor yet.

I stumbled upon another problem.

As I was busy troubleshooting the car I turned the key a few times with devices disconnected.
This resulted into six trouble codes according to the AHC datalist in Techstream.

I can open Techstream, open the AHC ECU, see tha datalist with (I guess) correct and changing data.
I also see "Trouble codes: 6". So I thought It was time to clear the codes so I go into the "trouble codes" menu.

Then it gives an error:
--------------------------------
Error code: 0x91020324

It's possible the requested function will work if you try again.
If the problem persists please submit an error report using the F12 key.
--------------------------------

So I tried again, and again, and again and I think you will get the idea by now.

I tried disconnecting the power of the AHC ECU and reconnecting, still nothing.

I thought it was the Techstream install in my Windows XP virtual machine. So I unpacked the MVCI driver and got it working on Windows 10 with another version of Techstream and tried again. Same error, same problems and just as slow as before.

A few weeks ago I could read and clear DTC's/trouble codes without a problem.

 

[NC-Grayson]

I have yet to dig into my issues yet...but am so thankful you've paved a way for me to dig into. ETA of steering angle sensor?

 

[Julian Stead]

Is your light still stuck on low with new sensors? You could disconnect the arms and move the sensors manually to see if there is any change. Move the sensors by hand and see if the light on the instrument panel goes to N or H. If you can't get this to change then I would presume your ECU can't read the data, for some reason. Broken wire, faulty software, bad connection and so on.

 

[Julian Stead]

I would hate to try and tell a electronic engineer what to do, but my thoughts with electrics on cars have been to try and test the circuit in as complete and in a working state as much as possible. That means by not disconnecting plugs and using a multimeter. Multimeters are great tools but they lie to you if you make a circuit open, you always want to try and put load in the closed circuit and test with a bed of nails as if there is resistance in the cable then you will see the voltage drop, or use a test light if measuring voltage if you need to make it open. A multimeter won't tell you if you have a bad connection or voltage drop through a cable if the circuit is open and no load is going through it.

I haven't got a wiring diagram on how the items connect together but I will presume that the height sensor signals go to the ECU. I would connect everything together, then put a bed of nails over the signal wire at the ECU, this will check every thing in the circuit other than the final connection to the ECU itself, I have a bed of nails for this, it just squeezes over the insulation and makes contact with the wire inside. If you are getting the signals back to the ECU that you are expecting when moving the sensors by hand then check the pins to the ECU are good then move on.

I suspect the software is being confused by something, this can be something like your sensors or door closed signals are not in sink. But concentrate on getting your L N H to move or even flash as if it is trying to move. If all signals and voltages and grounds are good at the ECU then try and replace with another, the problem with techstream is that it reads software, if the software is corrupt then you have no chance using this as a tool.

 

[Julian Stead]

Sorry I didn't read all the post, but the FSM gets you to test the steering wheel angle sensor at the ECU whilst connected, this is the correct way. You test everything at the ECU and go further out if something isn't right to investigate. It looks like the connections are accessible on the ECU without a bed of nails to make it easier. Good Luck and hope you find it soon.

 

[YvesNL]

Hi @Julian Stead thanks for your comments. I have been unclear on some things, so I will address them

Is your light still stuck on low with new sensors? You could disconnect the arms and move the sensors manually to see if there is any change. Move the sensors by hand and see if the light on the instrument panel goes to N or H. If you can't get this to change then I would presume your ECU can't read the data, for some reason. Broken wire, faulty software, bad connection and so on.

I just had a few error codes, the light was then stuck on N. The light to change to L or H would blink, but no action.
After clearing these codes the light is stuck on low again. It is logical to think that the ECU can't read the values, because the H, N, L value does not change.

However, if I connect techstream and show the datalist all three sensors display the correct data. So the ECU can read the sensors.

I would hate to try and tell a electronic engineer what to do, but my thoughts with electrics on cars have been to try and test the circuit in as complete and in a working state as much as possible. That means by not disconnecting plugs and using a multimeter. Multimeters are great tools but they lie to you if you make a circuit open, you always want to try and put load in the closed circuit and test with a bed of nails as if there is resistance in the cable then you will see the voltage drop, or use a test light if measuring voltage if you need to make it open. A multimeter won't tell you if you have a bad connection or voltage drop through a cable if the circuit is open and no load is going through it.

I haven't got a wiring diagram on how the items connect together but I will presume that the height sensor signals go to the ECU. I would connect everything together, then put a bed of nails over the signal wire at the ECU, this will check every thing in the circuit other than the final connection to the ECU itself, I have a bed of nails for this, it just squeezes over the insulation and makes contact with the wire inside. If you are getting the signals back to the ECU that you are expecting when moving the sensors by hand then check the pins to the ECU are good then move on.

I suspect the software is being confused by something, this can be something like your sensors or door closed signals are not in sink. But concentrate on getting your L N H to move or even flash as if it is trying to move. If all signals and voltages and grounds are good at the ECU then try and replace with another, the problem with techstream is that it reads software, if the software is corrupt then you have no chance using this as a tool.

No problem at all, you can correct me at any time. I do also make mistakes.

You're completely right on this. It is best to have everything connected. At first I checked the cables only, and after that I measured the system with all connectors in place. I didn't write this down correctly in my previous posts.

You can measure on the back of the ECU connector without disconnecting it (as per FSM) and that is what I did. I measured things like the height sensor with the system powered on. That way I could see if the voltages supplied to the ECU are correct and changing when I move the sensor.

For places where I can't measure on the connector because they were sealed I created a loop through the device that I wanted to measure. Take for example the stepper motors and the solenoids. I could measure all these devices while they were still connected and no connectors were loose.

Then there were stil places where I needed to measure but couldn't reach. For those cables I used some insulation piercing test clips.

Sorry I didn't read all the post, but the FSM gets you to test the steering wheel angle sensor at the ECU whilst connected, this is the correct way. You test everything at the ECU and go further out if something isn't right to investigate. It looks like the connections are accessible on the ECU without a bed of nails to make it easier. Good Luck and hope you find it soon.

That's right. The tests in the FSM start by measuring at the back of the ecu connector whilst connected and powered on. This gave 10+ volts on a pin that should only be 0-5v. So the Steering angle sensor is the thing that I suspect the most.

I haven't checked this input on the ECU yet. But being an automotive ECU I presume that the input is protected till at least 12v.

When I measure on the inputs at the ECU I get 10+v or ~0.33v. But in techstream the value is somehow changing from -830.25 to 542.25 deg quite smoothly (yesterday). But according to FSM the range should only be -364.5 to 355.5.

So, I am going to do some more checks on the steering angle sensor.

The second hand sensor I found was not available anymore. So If needed I'll order one from Toyota.

 

[NC-Grayson]

how did you manage to remove the ECU? I'm having a hard time...it's pretty tight quarters up there! does unbolting the ecu brackets and leaving the connectors attached give you enough room to test on the back of the connectors? I can't figure out the upper most of the two ecu mounting brackets.....no idea how to get that one unbolted

 

[Wilsil]

Wow, there is a lot of rust under the car.
I guess that's what you get when they use salt on the roads in winter.

Did you check that all door sensors are working?
You can't change the AHC in height when one door is open.