I took my 1997 Passatt for an MOT with no ABS problems. It failed on a split suspension gaiter that was replaced. After the MOT the orange ABS light was showing. I took it back and was told that it may be dirt on the ABS sensor due to above work. Checked, but light still on. Plugged into a hand held computer that could not give a reason for light showing . Taken to a VW dealer by the garage and a bigger computer found both sensors faulty and needed replacement (£105 plus vat each).This is put down to a coincidence by the garage.
1. Surely both sensors going at the same time is rare
2. Surely the above happening after going into a garage is more than coincidence
3. Is it possible the sensors were affected by computer checks that were done during the initial Mot?
Any direction I could get on this would be most helpful.
James
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James
When you say suspension gaiter i take it you mean the driveshaft cv joint gaiter. If so its very easy to damage the abs sensor when refitting the driveshaft on a4, a6 and passats.It is advisable to remove the abs sensor before removing or refitting the driveshaft on these vehicles.
Nothing during the MOT test should damage any part of your car.
Was the abs warning light on when you left the MOT station? If the answer is yes question why it didnt fail its retest.
You won't know the answers until the sensors are removed and you can inspect them for damage.
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The ABS sensors on this vehicle are all monitored by the management system.
If the front drive has been running with the ignition on then the rear sensors will record a fault due to them not turning.
Before you go to the expense of replacing sensors, have the ABS fault code cleared by the VW garage or a local mechanic with the diagnostic equipment.
If that does not clear the warning light then you can start to look for a fault. Hope this helps.
Tom
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Remember on the MOT your brakes are tested individually,end by end and side to side;this could trigger the ABS light but should go out later.
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Thanks for your replies.
Both nearside and offside front constant velocity joint gaiter were split and so replaced.
2 Lower wishbone arms were also replaced
If there is a chance of the sensors getting damaged in this process the evidence is pretty compelling as both sensors that were working prior to the MOT have now allegedly failed after the above work. The fact that there were no problems is surely proved by the fact that brakes were not an issue during the MOT.
I have the car at present as the parts have been ordered. Should I take it to VW?
If they are damaged, would I be able to evidence that they damage resulted in the above work being completed?
Regards
James
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To address the point raised on whether the light was on when I left the MOT station.
No - not until I pressed the brake pedal. It remained on until the engine was switced off and remained off after engine turned on again until the brake pedal was pressed again.
I doubt whether a full re-test was carried out after the cv joint gaiters and lower wishbones were replaced. The fail was on the cv joint gaiters only and the lower wishboines were repalced after I asked about the suspension clunking. Now improved.
James
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As they took it to a garage to identify the problem it is clear they they induced the problem either by damaging the sensors or the cabling. The chenged the wishbones and the gaiters which means they removed the drive shafts. giving plenty of opportunity to do the damage. Be firm and stand your ground they broke it they can fix it. The MOT proves it did not have the fault when you gave it to them. Good Luck. Regards Peter
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James,
This reminds me of a fault with an ABS unit on a SEAT I previously owned. Again after MOT but no work done in the area
of the sensors. At first diagnosis o/s rear sensor failed - replaced.(£80+) On journey home ABS light permanent glow. Next diagnosis the electrical connector plug on the ABS unit itself. One or more terminals had corroded badly for some unknown reason. Contacted SEAT after being told that some ABS units had had problems. (possible recall) but the VIN of the vehicle apparently proved that a faulty ABS unit had not been fitted. Total cost £400ish if I recall correctly. About 3 yrs later problem reoccurred.
Hope this may help.
don111
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Likely that MoT place damaged them during repair - but very difficult to prove!
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