2004 D3 ABS issue from bad to worse
 

Some of you know from another thread that for sometime now my D3 has had issues with the ABS controller ECU and a single wheel speed sensor failing to report once the car warms up, and generates an electrical fault in circuit error.

So today, I dove the car to an as yet unnamed establishment although at least one forum member knows where to get the ABS ECU removed and repaired.

Fast forward a couple of hours and the car is started in the workshop having been put back together but its obvious something is wrong. They then spend at least two more hours taking things apart and rechecking.

Things are now a lot worse than before, I've gone from having an intermittent (the car needs to warm up) ABS wheel speed sensor fault to a hard ABS error as soon as you start the car.

I've now got this error

http://wiki.ross-tech.com/wiki/index.php/01200

along with

Invalid being reported against all the wheel speed sensors in VCDS

The ABS, traction control light and a flashing red (!) in the speedo and one flashing in the top left of the widescreen DIS

plus when I get to 20mph I get a parking brake error which remains on until I slow to a stop only to beep and return again at 20mph.

I've not named the establishment yet as they are working with me to fix the issues. As they are 1.5 hours from me, I needed the car to get home otherwise they would have carried on working on it tomorrow. They are going to call me when they have some news to get the car back in, but they are currently saying the electronic module may need replacing but they did not know about the parking brake error.

I'll attach a VCDS scan once I have redacted the VIN number. I have cleared all the faults from this scan, only the ABS fault and parking brake return.

I drove the car home, leaving them at 5.30pm.

Here are two full scans

One is a scan once I got the car home, obviously tainted by the removal of the ABS ECU

The second one is a scan after a code clear but before starting the engine, the 01200 error returns once started.

I think they've borked the ECU, heck I've even tried disconnecting and reconnecting the battery since to see if that clears the fault.

Tomorrow I am going to take the connector off the ABS module and check they have not bent any pins.

Stupid question, but the fuses have been checked ?

Supply voltage is a pretty distinct fault. It means, there isn't +12 where there should be. There aren't too many reasons for that. (bent pin at a push, but you're way more likely to kink a thin data pin than a thick power one ?)

If the ABS module was toast, you'd likely not be able to talk to it.

ABS, is also responsible for generating the main speed signal in the car which is used for virtually every other module - Air suspension raise/lower, Sat Nav speed pulse, Steering for servotronic, parking brake to know when to release, PDC to auto switch off, ACC for obvious reasons !

So, I think it could look way worse than it actually first appears....

I've had a faulty ABS module before, and the parking brake bleated every time I set off (very annoying) but its just being over cautious as it knows there's an ABS fault and it may not know (or trust) the current speed of the car. That fault went as soon as I had the ABS module 'reconditioned' (which basically involved breaking it open, and resoldering all the dry solder joints on the board that occur as a result of it being physically located right next to the coolant header tank for the last decade or so, is my understanding..... This is why it works when cold, but once the coolant warms up and expands the joints again, it fails I believe)

There is a 60amp fuse that feeds the ABS module, in addition to other, smaller feeds.... I suspect that juicy feed it want makes the ABS pump and valves dance when needed.

I would defo be checking all aspects of that 60 Amp feed, its quite probably that could be at fault, but the electronics of the module could be powered and happy.

IT, you were spot on with the fuse hunt.

They did check fuses, but I did not remember them going into the passenger side end of dashboard one. I know they did the drivers side as there is grease on the cover.

In the passenger side fusebox is a 25 Amp fuse labeled as Electronic Stability Control, it had blown to pieces. Luckily I had a spare, so replaced it and fired up the car. Result no faults showing on dashboard, I then left the car idling to see if the fuse blew again and it did not so I took it for a drive. Normal service resumed, a clear dash with no fault lights even after going for a drive.

They are familiar with most VAG group cars, and I think mine was the first A8 that issues with. I guess they did not know about the other fusebox, so did not check that side.

I'll email them shortly and let them know my findings, and save them trying to source a replacement module.

A perfect example of why this forum is fantastic, and such a vital source of information and experience for us A8 owners :love:

I could sense your despair mannyo after the disappointing visit to the unnamed establishment, you'd been looking forward to them being able to resolve your ECU "issues", and it appeared they'd failed miserably.

Share your findings on here, along comes IT armed with his extensive knowledge and experience...a short while (and no more expense) later all is good in the world again ++++++

Thanks

I was a little worried yesterday, until Ians post, and now quiet relieved to have a normal looking instrument cluster.

What a great result, so happy its up and running properly again +++