Jim @ EuroWerks

Anyone that knows can help, but adrian I am looking forward to getting your book. Where do I order one? Meanwhile back at the shop I've got an 89 C4 the abs light comes on while driving intermitantly. Usually easy straight line driving brake warning does not come on. My concern was that my cust. brakes may fail with this light on. However I think that since the brake light isn't coming on then that should not be the case. Also the light won't go off unless you cycle the ignition switch while driving. I ck'd for faults however the pst2 did not even recognize the system as being there. Sometimes the light won't come on for miles and miles. Some times it comes on every 3 minutes. I've checked alot.Any help would be appreciated.Sorry if this seems like you just talked about this but the symptoms seem different.

Adrian

Dear Jim,
www.bentleypublishers.com
Are you just getting the ABS light? No PDAS light? Try engaging the traction control program when the ABS light has come on. This should bring on the PDAS.
The most common cause of this fault is the longitudinal accelerometer in the centre tunnel forward of the gear stick. Access via a small panel on the right side of the tunnel.
This WILL NOT affect normal braking. If either the PDAS or ABS fails the corresponding system is disabled completely. For the ABS the three solenoids are closed and power is removed so they cannot open.
If the problem occurs whilst driving along as you suggest as against when you start up you are looking at a dynamic component problem. In the C4 that means the wheel speed sensors and the accelerometers. If the wheel speed sensrs go both the PDAS and ABS come on at the same time. If just the ABS then it is more than likely the accelerometer which only feeds the ABS circuit.
The brake light is a pressure problem or fluid level problem. The ABS does not use pressure it relieves it and does not care about fluid levels.
I cannot help you with your test equipment problem I am afraid. You may need an adapter cable for the control unit in this case. I am not actually familiar with a pst2.
Ciao,
Adrian
964C4

JoeW

Jim, the "Encyclopedia" is available through the publisher, Bentley (www.bentleypublishers.com), or Amazon or Barnes & Noble.com, etc. I got mine from B&N for $55. Worth a lot more, imo. In fact I haven't been posting much of late .... reading and trying to grasp it all w/o a car to look at! J

Jim @ EuroWerks

Thanks Adrian I'll talk to my cust shortly and you will get credit. I'll order you book monday

Adrian

Dear Jim,
You are the fixer no need to credit me for it. Thanks for the kind thought but it is not necessary. You are using resources available to help in the diagnosis. That is what good troubleshooting is all about.
Ciao,
Adrian
964C4

Jim @ EuroWerks

To late it's already done!

Jim @ EuroWerks

Did you know that this sensor retails for 808.00 us dollars?

Jim @ EuroWerks

I assume the arm inside this sensor should not be hanging up as it is. I have bent the arm to make its travel free now lets go test drive.

Adrian

Dear Jim,
No it should not hang up it must move freely backwards and forwards measuring acceleration.
Ciao,
Adrian
964C4

Jim @ EuroWerks

No light yet!

Jim @ EuroWerks

Adrian, once today after repair, the antilock and allwheel drive light came on and stayed on at start up. stayed on till the phone rang. When I got back the light didn't come on. I'll keep digging. Thats the first time its come on without the car moving.

newmoe

Sorry to barge in on this but what size tires are installed on the customers car?
Are they within the size limits to avoid triggering the ABS sensors?

Just a thought..

(yes Adrian i really did read the whole thing)

Adrian

Dear Jim,
Was the little yellow led inthe centre console also on or just the two warns.
Battery voltage can play a role here.
If the systemis failed without moving off it is telling you that either the control unit has a problem or the dual solenoid valve has failed or you have a voltage problem.
The accelerometer still could be the problem because if it is shorted out somehow the 5V supply line from the control unit will be down and the control unit will detect this and fail itself.
I am not sure if you have had the control unit connector off but I would remove it and check for corrosion on the unit pins and in the connector.
I used to get this every start until I found and clean the corrosion off the pins.
The PDAS/ABS can take a lot of punishment including being filled with water but it is very sensitive to voltage monitoring.
Have the seats been replaced or removed and reinstalled?
I would still have the accelerometer as my number 1 suspect. It is easy to check the 5V supply from the control unit.
Next time you get the lights on and they stay on, go for a short drive, see if they go out under acceleration. If they do that is voltage related or the accelerometer still playing up.
Ciao,
Adrian
964C4

Jim @ EuroWerks

Adrian, the seats havenot been pulled that I know of. However, the alt was just replace and I understand the shop that installed it not only had trouble but now the cust. is also complaining of voltage spikes. I have been monituring this with a volt meter while driving and have not wittnessed it. Also, I ck'ed the term 61 (blue) wire into the ABS controller and noticed no spike or drop in voltage when the light came on. I am still thinking about the alt. can you tell? I will ck on the sensor some more I really appreciate you trying to help but realize the car is in my hands and you are across the big pond. Thanks for the effort I will keep trying!

Jim @ EuroWerks

Thanks newmoe, I ck'ed the tire sizes 1st. And, pulled and ck'ed all the sensors for debre.Debre, is that a french word?