Finding faulty ABS sensor

[mnkiboy]

I have a 2003 Volvo V70 with a failing ABS / Wheel speed sensor. The traction control keeps cutting in even when driving gently. All wheel's and tyres are identical and the car was performing fine up until about a week ago. Tyre pressures have been checked and double checked, so i'm sure it's a sensor.

Question is how do I determine which of the 4 sensors is at fault? The issue originally only occurred when going round tight right hand bends eg roundabouts. It's now getting to the point where even in a straight line the TC is cutting in. The ABS light hasn't lit so i'm guessing no faults are stored.

[b2hbm]

I used a multimeter to find the faulty sensor on the wife's Puma a couple of years ago. In that case it was quite simple, I just went round the wheels, unplugged the sensor and put the meter across each one.

But the ABS light was on permanently which is usually the first indication of a failed sensor. If yours isn't coming on, then the problem could be elsewhere, maybe a corroded or loose connection ?

Brian

[stevieturbo]

I assume the ABS lamp does sill turn on for a period when you key on ?


ie, someone hasnt removed the bulb ?

It could be a sensor, wiring, trigger wheel, ecu etc etc

It should have some form of self diagnosis if you can find someone with a suitable scanner. It should also allow you to view the signals/readings from each corner

Failing that, a multimeter might give some indication, but really you'd need to scope each wheel and make sure the signal is regular and repeating with no glitches.

[mnkiboy]

The ABS light did come on this morning, but as OBD2 doesn't include ABS codes it doesn't really help me.

I'll try plugging a multi-meter in to each one and see if I can identify the faulty one. Seems to be intermittent though so might not be easy.

[Rollcage]

False activations are more likely to be a reluctor ring issue, rather than the sensor itself. If the sensors fail, then usually the AbS shuts off completely.

[TheEnd]

Yep, a knackered sensor would mean the light comes on on starting, and before moving as it spots the resistance difference.
If it needs the car to be moving, then it is plausibility of the signal that is triggering it, sometimes things like metal swarf can get in the way, or a worn or damaged wheel bearing.

[stevieturbo]

mnkiboy said:

The ABS light did come on this morning, but as OBD2 doesn't include ABS codes it doesn't really help me.

I'll try plugging a multi-meter in to each one and see if I can identify the faulty one. Seems to be intermittent though so might not be easy.

It certainly wont be easy without the correct tools.

A visual check of the trigger rings might reveal though.