Random ABS warning.

[Ken Long]

On our trip to Scotland last week we had the ABS warning go off. We were driving in fairly unpleasant conditions at the time. The photo below was taken at Sandbach services, it was probably only 15 minutes after setting off again that the warning sounded.

After pulling off the M6, switching the engine off and restarting the warning had cleared. The weather improved as we headed north but the warning went off again as we approached Carlisle, having passed the turning for @timmus ironically! Again a stop/start reset it. We pressed on and the warning made no reappearance until we within 500m of our accommodation in Laggan. My brother in law had also had ABS warnings on his 21 plate A class Merc so we wondered if the weather early in the journey had caused an issue with the ABS sensors.

We used the car all week, probably doing about 500 miles with no reoccurence of the issue. On our journey home yesterday, it suddenly came on, just as we were approaching our lunch stop. On setting out again, we completed the rest of the trip (maybe 220 miles) with no issue.

On occasion during the week I had to pull up sharply on less than perfect surfaces and the ABS seemed to work fine. The brakes pulled up evenly and the car at no point felt unstable. Is it likely that the snow/ice has affected the ABS sensor? Where is the ABS sensor mounted? Is it front or rear? I ask because the day before we set out the rear shocks and springs were replaced and I wonder if something was disturbed during that process?

Any insight very gratefully received.

 

[Robin_Cox]

the ABS sensors are in all four bearing housings. If you are able to see the front bearing housing, the sensor is screwed into the top of the casting so that the end of the sensor is located adjacent to the magnet ring on the bearing itself. Then the wire for this runs up the suspension strut and into the loom - I wonder if you've maybe got slight damage to the wire on one of the corners that was transiently causing the ABS system to get unhappy because of a short to earth or similar owing to the amount of water and slush in the driving conditions? On the rear I think the sensor wire goes into the back of the drum backplate adjacent to where the brake pipe is joined to the rear of the brake cylinder.

control unit for abs; speed sensor Audi A2 (A2) 2003 year Audi EUROPA 927000

control unit for abs<br/>speed sensor Audi A2 (A2) 2003 year Audi EUROPA 927000 spare parts

audi.7zap.com

the location where the ABS sensor screws into the front casting can be seen on the left hand bearing housing in my image below :

https://www.a2oc.net/community/index.php?attachments/img_0794-jpg.78636/

 

[dj_efk]

I wonder if a VCDS scan would reveal which wheel sensor / wiring was the issue - if it’s that. Anyone know?

 

[birtyA2]

On our trip to Scotland last week we had the ABS warning go off. We were driving in fairly unpleasant conditions at the time. The photo below was taken at Sandbach services, it was probably only 15 minutes after setting off again that the warning sounded.

View attachment 105845

After pulling off the M6, switching the engine off and restarting the warning had cleared. The weather improved as we headed north but the warning went off again as we approached Carlisle, having passed the turning for @timmus ironically! Again a stop/start reset it. We pressed on and the warning made no reappearance until we within 500m of our accommodation in Laggan. My brother in law had also had ABS warnings on his 21 plate A class Merc so we wondered if the weather early in the journey had caused an issue with the ABS sensors.

We used the car all week, probably doing about 500 miles with no reoccurence of the issue. On our journey home yesterday, it suddenly came on, just as we were approaching our lunch stop. On setting out again, we completed the rest of the trip (maybe 220 miles) with no issue.

On occasion during the week I had to pull up sharply on less than perfect surfaces and the ABS seemed to work fine. The brakes pulled up evenly and the car at no point felt unstable. Is it likely that the snow/ice has affected the ABS sensor? Where is the ABS sensor mounted? Is it front or rear? I ask because the day before we set out the rear shocks and springs were replaced and I wonder if something was disturbed during that process?

Any insight very gratefully received.

As others have stated it may be that you have an intermittent wiring related fault, but looking at the conditions it’s just as likely that damp in one or more sensor connectors or indeed slush getting in there could have caused these sort of issues. Will be worth a scan just to see what was reported as a first step

 

[Ken Long]

I'll try and get a scan sorted I think!

 

[Sylvester]

I've had similar issue, but the abs and epc light came on at once, along with 1 time randomly activated abs, which wasn't fun of course, apart from looking at the warning lights though, the car didn't miss a beat. I always have the scanner in the glove box, and it'd showed the YAW sensor intermitten fault, so I know it's need changing.
But as mentioned above, scanning is the first step. Also don't be surprised if a lot of fault codes will show, as the cccu can store old codes, if they weren't deleted before. So make notes of them, then delete, then scan again.

 

[PlasticMac]

I've had similar issue, but the abs and epc light came on at once, along with 1 time randomly activated abs, which wasn't fun of course, apart from looking at the warning lights though, the car didn't miss a beat. I always have the scanner in the glove box, and it'd showed the YAW sensor intermitten fault, so I know it's need changing.
But as mentioned above, scanning is the first step. Also don't be surprised if a lot of fault codes will show, as the cccu can store old codes, if they weren't deleted before. So make notes of them, then delete, then scan again.

Tip, when the scan is complete, click on the "Copy Report" button, and open word pad, and "Alt v" to paste the report into the text document, then "save as"
Mac.

 

[Kyojitsu]

Former Land Rover owner here - I only mention it because ABS lights were often triggered on my Discovery due to very slight variances in voltage detected from the sensors especially off road. Mud and road crud/slush could easily trigger the ABS warning with no permanent fault recorded. It's probably nothing to worry about but as others have said get a scan if it reassures you.