Pug306HDi - ABS warning light

Honest John Back Room » Technical matters
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Sat 3 Sep 2005 14:45
Pug306HDi - ABS warning light - MikeC
Hi, car is a 2000W 306 HDi.

My ABS warning light is coming on, it does the ignition check for a few secs and goes out ok, but will then come on when I drive, some times as soon as I start rolling but others it takes up to 5 miles. Also braking hard (ie stabbing them at 30) will make it come on as the brakes are released. Onces its on it wont go off until you switch off and restart.

My question is could a difference in wear of the front tyres (one is brand new the other is nearly at the end of its life so there is probably ~5mm difference (195/55/15)) be enough to throw the sensors as the wheels will be rotating at slightly different speeds?

I've booked it in to get the ECU read but just thought it could simply be the tyres. To add further complications the car was involved in an accident recently (some one drove into the side of me - front nearside wheel area took the initial impact) - hub/wheel bearing/suspension etc was replaced so it may be related but I don't want to jump to conclusions yet.

Any advise would be appreicated. Mike.
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Wed 7 Sep 2005 01:49
Pug306HDi - ABS warning light - boab67
The abs wheel sensor may have been damaged in the shunt or the wiring leading to the sensor may be broken,an ECU read would probably show this up.
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Thu 8 Sep 2005 01:00
Pug306HDi - ABS warning light - Cyd
Damaged sensor or split reluctor ring. Front left I'll bet!
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Thu 8 Sep 2005 23:52
Pug306HDi - ABS warning light - MikeC
Thanks for the advice so far. I'll report back on monday with the fault found. Light is now triggered by speed bumps and reversing. Local tyre outlet suggested 'in theory' the difference in wear could cause the problem but very unlikely. I feel another trip back to the accident repairer coming on!
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Fri 9 Sep 2005 10:44
Pug306HDi - ABS warning light - Cyd
Differences in tyre wear WILL NOT 'in theory' cause the ABS to either cut in or the light to come on. ABS systems are designed to account for these differences in wheel rotation. Anyway the ABS system is looking for rotational deceleration of the wheel not its speed. That mechanic doesn't know what he's talking about.

If you can lay your hands on an ohmeter, measure the resistance of the front sensors from the connector nearest the ecu (usually on the inside of the inner wing somewhere). You should get about 1000 to 1500 ohms. Also check the wiring and the sensor visually for damage before you go back to the garage - you never know the fault may be obvious.
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Mon 12 Sep 2005 21:34
Pug306HDi - ABS warning light - MikeC
The fault, as we guessed, is the NSF wheel sensor. Thanks for the advise guys.
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