ABS malfunction Lamp

Hello everyone!

I've tried to find an answer online, but I did not, so I am here to ask for help.

I drive a 2011 c3 1.4, and recently I've decided to replace front brake discs and pads.

The screw that holds brake calliper in place was extremely hard to unscrew so I used an jackhammer to beat it and loosen it.

I replaced both discs and brake pads on front wheels and when I started up the car, I've got an ABS malfunction lamp light up. NOTE: I did not have that problem before replacing the discs.

I've driven the car for a day and light disappeared, but then after two days it lit up again.. I went to an mechanic and computer said it is problem with the left abs sensor so I went to buy new one, replaced it, but problem appeared again when I started up the car.

Sometimes it does not appear immediately when starting the car, but after driving over 20km/h it lights up.

What to do?

You only said left sensor. Front or rear?

If the light only comes on when the car is moving then the problem is probably not the sensor or wiring. Besides, you said you replaced the sensor. The problem seems that the ABS system in not getting a proper signal or no signal at all (when it is getting a signal from the others) but it knows the wiring is OK.

Not familiar with the later model C3's but my guess is a problem with the bearing. The bearings contain the magnets that the sensors pick up to detect the wheel speed. It could also be corrosion or mud buildup inside the wheel knuckle between the bearing and the sensor.

Another suspect is the big electrical connector that plugs into the ABS module on the bottom of the hydraulic block. This can get corrosion in it. Remove the connector and spray with electrical cleaner.

questions-about-a-citroen-c3-not-relate ... t4513.html

Topic showing rear abs sensor ring fix. ABS sensor fault - not due to the sensor itself being faulty. (P0500)

Ozvtr wrote: ↑Mon Aug 16, 2021 12:21 am You only said left sensor. Front or rear?

If the light only comes on when the car is moving then the problem is probably not the sensor or wiring. Besides, you said you replaced the sensor. The problem seems that the ABS system in not getting a proper signal or no signal at all (when it is getting a signal from the others) but it knows the wiring is OK.

Not familiar with the later model C3's but my guess is a problem with the bearing. The bearings contain the magnets that the sensors pick up to detect the wheel speed. It could also be corrosion or mud buildup inside the wheel knuckle between the bearing and the sensor.

Another suspect is the big electrical connector that plugs into the ABS module on the bottom of the hydraulic block. This can get corrosion in it. Remove the connector and spray with electrical cleaner.

Sorry, I forgot to tell exactly, but it is the left front sensor that computer shows..

I will go and change wheel bearing tomorrow morning to see if it solves the problem.

Thanks for the reply!

BrtMarkan wrote: ↑Mon Aug 16, 2021 9:28 pm

Ozvtr wrote: ↑Mon Aug 16, 2021 12:21 am You only said left sensor. Front or rear?

If the light only comes on when the car is moving then the problem is probably not the sensor or wiring. Besides, you said you replaced the sensor. The problem seems that the ABS system in not getting a proper signal or no signal at all (when it is getting a signal from the others) but it knows the wiring is OK.

Not familiar with the later model C3's but my guess is a problem with the bearing. The bearings contain the magnets that the sensors pick up to detect the wheel speed. It could also be corrosion or mud buildup inside the wheel knuckle between the bearing and the sensor.

Another suspect is the big electrical connector that plugs into the ABS module on the bottom of the hydraulic block. This can get corrosion in it. Remove the connector and spray with electrical cleaner.

Sorry, I forgot to tell exactly, but it is the left front sensor that computer shows..

I will go and change wheel bearing tomorrow morning to see if it solves the problem.

Thanks for the reply!

The wheel bearing magnetic ring won't fail.

It will more likely to be interference of the signal due to dirt or dust.

Try cleaning first, changing a good bearing may not be necessary.

Update


I've tried cleaning it but ABS lamp lit up again when I started the car, and we noticed a small dent in the bearing outer side (the one that sensor points to), I have no idea how did it appear there.

So we decoded to change the bearing, and after attaching everything back on the car, wheel, etc. I start up the cat and bang, ABS lamp lights up again, but luckily it turned off as soon as I drove out of the garage.

So that was the problem, bearing.

Thanks everyone!