AHC sensors

[Zeusv8]

Ok I now drive a low rider and probably won't get a proper reading but I'll try anyway! I have downloaded a Ecu terminal guide and realised that engine idling is controlled by this Ecu as well!!!!!!!! That was problem number 1! Am I right to conclude that this Ecu is on its last???? It is now got the LO light on and is still flashing off and the car is on its arse nearly !!!!IH8toyota!!

 

[Zeusv8]

I have 1.99 volts on s8 no2 can't really see where sensor is sittin due to it being low! Next???Thanks.James

 

[Zeusv8]

The connector block near to the bulkhead with the black and white and blue and white cables in it is dead 0.00 volts engine off/on. Any ideas?? Checked fuses too! I'm finding it difficult to "Hotwire" the pump as its awkward to get to and the connector pins are very close together close enough for me to short something or me!!!

 

[uHu]

Ok I now drive a low rider and probably won't get a proper reading but I'll try anyway! I have downloaded a Ecu terminal guide and realised that engine idling is controlled by this Ecu as well!!!!!!!! That was problem number 1! Am I right to conclude that this Ecu is on its last???? It is now got the LO light on and is still flashing off and the car is on its arse nearly !!!!IH8toyota!!

The t0yota ECUs don't normally fail unless there is some external influence, like water.
I don't think this ECU controls the idling. That is done by the engine ecu behind the gloves compartment. Are you at the right one?
How come the tail end is low now? what happened.

 

[uHu]

The connector block near to the bulkhead with the black and white and blue and white cables in it is dead 0.00 volts engine off/on. Any ideas?? Checked fuses too! I'm finding it difficult to "Hotwire" the pump as its awkward to get to and the connector pins are very close together close enough for me to short something or me!!!

Have you checked the 50 A ahc fuse, and the ahc relay? Those two supply the juice to the pump when the ecu gives a signal to the relay.
There is also the AHC-Ign fuse and the AHC-B fuse.

For checking the pump motor with 12 V "direct injection", you have to find test leads or plugs that fit the tiny pins in the plug. The conductors supplying the pump motor have the colours blue with black and white with black. (that's for RHD mfg date 2000/10 to 2002/7)

 

[uHu]

I have 1.99 volts on s8 no2 can't really see where sensor is sittin due to it being low! Next???Thanks.James

Hard to say what's next. I don't have any info on what volt means what height, but this probably means that the sensor says the rear is a bit low.
It works like this:
At Normal height it is supposed to be 2.5 volts, and at 1.99 volts the pump and valves would kick in to bring it to 2.5 volts. Since it is not doing this, there is either some kind of input to the ECU saying "don't do anything" - like, e.g doors are open, terrain is too un-even (big difference between left & right sensors), brakes are on continuously, erroneous input from some sensor or valve, etc; OR there is something wrong with the pump or power supply.

We have established that there is some kind of signal from the rear sensor at least. That's good. From the front sensors it looks like there is an ok signal according to the info from the diagnostics.
Now I believe the easiest next step is to verify power supply to the pump motor, the motor itself, and if that runs, that the pump actually pumps.

You could also check the fluid pressure and temperature sensors, as a malfunction could tell the ecu that those values are too high.

 

[Zeusv8]

It went to low on its own and won't go back to normal even at speed over 30kph. I checked the 50amp at the main box in engine bay I'll check the rest in the morning. I'll try to get some thing that will plug onto connector and try getting 12v to the pump. The other two plugs on the pump which I presume are sensors both read around 5 volts so they are getting juice at least!Thanks,James

 

[Zeusv8]

All fuses intact and the pump works ! Is it time to phone Julian for an OME kit??

 

[Graham]

Hi,

You certainly are not the first to throw your hands up in dispair at the 100 series AHU.

Even guy's where the AHU is working normally, have decided to remove it all in favour of a more traditional set up.

If you up Scotland way, perhaps a call to Paul, at West Coast 4x4 would be OK, as I am sure they will be a whole lot closer, just in Southport area, NW England.

Gra.

 

[uHu]

In the FSM, under "diagnostics > Active Height .... > Terminals of ECU" you can find all the voltage values for the different inputs to the ecu. And further on you find the fault finding procedure specific for each sensor or input signal.

Better check the front gate solenoid first then. If you unplug 5-pin plug of the valve assembly, you can measure continuity of each of the four solenoids. Pin # 2, Blue w Yellow, is the common, and each of the other four pins should have continuity (low ohm) to # 2. Front gate is pin 1, Violet.
When you unplug the valve assembly, you might find that the problem is in the plug, although the t0yota plugs normally keep up very well.

You can find the same signals/leads up at the ahc ecu, at plug S9, pin 24 as common, 7 is front gate, the other three at pins 8, 20 and 21. Same colours as in the 5-pin plug at the valve assembly.

 

[Zeusv8]

Ok I have no reading at no 1 on the 5 pin plug but have a reading of about 150 on the rest if I have used the multimeter right! There is a reading at the Ecu for pin 7 of about 150 same as the rest of the points mentioned. What does this mean?? Thanks for your help!

 

[uHu]

It means that it doesn't make sense. I would do it again, and also check the values at the S9 plug with the plug underneath out if I got the same result again. Did u have the S9 unplugged when measuring?

Another option is that either the schematics is wrong, or that I didn't read right. Have you checked yours?

But, no continuity in the front gate valve solenoid would match the diagnostics trouble code, so maybe you actually need to have it changed. Check the cable & plug again first.

 

[Zeusv8]

I not even sure I'm using the multimeter properly!! The values I'm getting keep going up the longer I leave it connected to the terminals. As for schematics I've looked through thousands of pages and links and can't see the relevant info. The plug was still connected to the Ecu at time of testing and the plug at assembly was disconnected. I take it this is wrong and both should be unplugged and tested again?? As for a solenoid , are these replaceable? I apologise for being a pain in the arse but it's like driving a go kart!!
Forgot to mention that on startup this morning it kicked in and dropped the front suspension,made an intermittent noise for 20secs and went back to usual flashing off and sitting at low.

 

[uHu]

The plug was still connected to the Ecu at time of testing and the plug at assembly was disconnected. I take it this is wrong and both should be unplugged and tested again??
As for a solenoid , are these replaceable?

Well, it depends. When checking the valve solenoids in the valve body underneath, you should check through the nearest plug, which then has to be unplugged. You should not see any variation in the reading - it is a coil you are measuring - it doesn't change unless u use ac or heat it up.

When checking up at the S9 plug, in case you find that the solenoids in the valve body are all ok, you can check the wire harness down to the valve body. That could be easier with the S9 disconnected from the ecu.

The valve body is replaceable as one unit. Most difficult part would be to get the pipes disconnected without damage.

 

[Zeusv8]

Just for closure on this nightmare!!.I have decided to rip out this system as I am getting stupid prices for replacement assemblies.£180 plus delivery for a 14 year old untested,unwarranted part is seriously taking the piss so it's bye bye AHC and hello OME. Thanks Uhu for your help and patience!Thanks to everyone else who popped in for a gander and a post! I will be removing the system to sell for parts to offset the costs a wee bit. I will post up the condition of spheres and shocks when I'm done.cheers.James

 

[Dark Dude]

James

Good luck with the change over. You're not the first and you won't be the last to kiss goodbye to the AHC.

Shame!

John