I had the car out last week on a green laning day, did 160miles in total, drove 60miles there on normal a roads, no issues, and another 25ish miles of lanes. towards the end of the day the ABS fault appeared. It appeared on startup, not while driving.

This issue plagued me last winter, and something i noticed back then was it only ever appeared upon starting the engine. NEVER when driving. If you started the car without the fault, you'd be fine for hours. Usually if it appeared, a quick reset with nanocom and power cycle and you'd be fine. Occasionally it would stick around but would clear later. I should mention this is a Wabco D system with the black ECU.

I had a hunch there was something battery/power related, my battery was very weak/old/knackered. I was having starting issues at the same time. A short drive to get some juice in the battery then it would reset was my thinking... In the spring i swapped the battery and added a solar charger. After that, i've never seen the issue again until now.

The fault code itself is Front Right Sensor - Short to Another Sensor. It ALWAYS says it has occured 012 times.

If you check sensor voltages in the live data, all sensors are reading about 2.2v, including the front right.

So this time it seems worse. It appeared on that green lane, i reset it and it reappeared immediately on restarting the engine. Tried another few times on the way home, didnt get anywhere. Left it until today as i had a dump run to do with the trailer. Popped out earlier, reset the code and sure enough it came right back. I left it running for 10minutes while i pumped up the tyre, and while i was waiting on the compressor i pulled the three connectors out of the ECU and checked them for corrosion, all looked fine. With everything plugged in, there was now a zillion fault codes as to be expected.

Cleared codes, drove it down the street, lights all went out. Great stuff. Quick loop of the block, parked back in the drive to hook up the trailer and when i restarted it the fault came back.

Has anyone seen anything like this before? I'm tempted to swap the battery again, with a brand new one this time, on the vague idea that maybe the poorer weather means the solar panel isnt doing much and this battery is also a bit tired... But i also dont want to waste money replacing a battery which seems to crank up the engine just fine, if its actually a faulty ABS ECU or something!

Found mention on another forum of similar issue, although rear left, indicating a problem with the ECU.

Marty seemed to have a fix, but not sure if hes still around these days? I've done some SMD work before, so i'd give repairing it a crack given the price of used ones on ebay!

The ABS system does two self checks, the first when you initially turn the ignition on when it checks for the correct resistance on each wheel sensor, the second once you start moving when it checks for the same speed from each sensor. If it comes on when starting the engine and not with the ignition, that would suggest the battery voltage is dropping during cranking. Although that usually brings on a Gearbox Fault not ABS Fault.

I remember Marty saying something about ECU faults on the Wabco D system as he was offering a repair service on them. I assume you've done the C to D upgrade as a pre-99 car would have originally have had the Wabco C system with 2 wheel TC rather than the D with 4 wheel TC.

Yeah I converted it to D last year when the ABS modulator broke. I have a feeling this issue has been niggling ever since I converted it.

I will maybe need to try and get hold of another ECU, but being able to fix this one would also be a big bonus.

Just no real info on what the fix actually is. Bad filter caps maybe?

Afraid I've no idea what the fault or fix is, but a logged error of one sensor short to another is the symptom.

Unfortunately Marty managed to crash his own website and hasn't got around to writing a replacement yet but his old one did detail the problem.

I had pretty much the same symptoms on my 02.
It would come and go and could be cleared with Nano.
Drove me round the bend for several years.
Finally faulted out permanently on an icy road at 2am....on Christmas Day!!
Lots more trouble shooting and it turned out to be the RT front wheel bearing.
It was very worn out but showed no odd symptoms and made no noise.
Hitting the ice, it must have really twitched hard over and it dislodged and pushed back the sensor!
New wheel bearing and problem gone.
The sensor shorted to sensor fault was a red herring for me.
Usually it would come up with an abs fault and show no errors on Nano.
Live readings showed signal, resistance was fine.
Jack it up and give the front wheel a good wiggle ( a piece of timber under the wheel to pry it up and move it sideways worked for me)
Good luck!

Gilbertd wrote:

Afraid I've no idea what the fault or fix is, but a logged error of one sensor short to another is the symptom.

Unfortunately Marty managed to crash his own website and hasn't got around to writing a replacement yet but his old one did detail the problem.

What is the URL? A copy of his old website should still be accessible on the Wayback Machine just like you can access all the useful guides on rr.net that were deleted by the owners https://web.archive.org

Bolt wrote:

I had pretty much the same symptoms on my 02.
It would come and go and could be cleared with Nano.
Drove me round the bend for several years.
Finally faulted out permanently on an icy road at 2am....on Christmas Day!!
Lots more trouble shooting and it turned out to be the RT front wheel bearing.
It was very worn out but showed no odd symptoms and made no noise.
Hitting the ice, it must have really twitched hard over and it dislodged and pushed back the sensor!
New wheel bearing and problem gone.
The sensor shorted to sensor fault was a red herring for me.
Usually it would come up with an abs fault and show no errors on Nano.
Live readings showed signal, resistance was fine.
Jack it up and give the front wheel a good wiggle ( a piece of timber under the wheel to pry it up and move it sideways worked for me)
Good luck!

I did actually buy a new sensor last year, its sat on my desk still. I can certainly check the bearing ofcourse.

However the reason i never changed the sensor is i realised the issue never occured when driving. If it was a sensor issue (or a bearing issue as you describe) you'd expect the fault to come up when driving along. Instead it only ever appears at startup. As the other week while green laning, it was totally fine for hours of tracks and whatnot. We stopped on one particular track for a while as someone had managed to slide off the edge and needed recovered. It was only upon restarting the car after having been sat for a while did the error appear. But since then its been particularly sticky.

I suppose i could just fit the sensor anyway, should be a quick job, and i can check the bearing etc while in there.

I've ordered some new ground straps and battery terminals. I'm going to replace the battery and fix the tired bits i've been meaning to sort for a long time. Even if it doesnt fix it, it will rule it out and hopefully permenantly sort the battery issues i've been having.

I may well have to bite the bullet and just buy an ECU from ebay, my MOT is due next month so i dont have endless time to investigate the possible repair of the existing unit.

nigelbb wrote:

What is the URL? A copy of his old website should still be accessible on the Wayback Machine just like you can access all the useful guides on rr.net that were deleted by the owners https://web.archive.org

www.p38webshop.co.uk