Abs Sensors

[Rev Jules]

My son is having trouble tracing a faulty ABS Sensor for an MOT test, what should he look for.

Cheers.

Rev

[Les4048]

Originally Posted by Rev Jules

My son is having trouble tracing a faulty ABS Sensor for an MOT test, what should he look for.

Cheers.

Rev

I was going to say a faulty ABS sensor Rev but I’ll refrain sorry mate couldn’t resist, the force was strong

[Avulon]

Firstly He'll need to connect a multimeter to test the voltage pulses from each sensor to find which one is the problem. FrenchMike's photo here show's how it should be connected. Jack the car up and spin the road wheel being tested slowly to see the meter react.



Determine which wheel gives faulty readings. He may have to resort to marking each wheel for every pulse to see which wheel is missing pulses. Hopefully though it will be obvious - I.e. one wheel not generating any pulses or very few.


Once the faulty wheel is found then it's down to whether it's the sensor or the reluctor. Not so easy to test for as removing the sensor very often is destructive anyway. The reluctors are built into the wheel bearings, so one method is to change the sensor and see if that fixes the issue, if not continue on and change the bearing.






P.S - Using T4 or Toaf could be much easier if you have access

[David Lawrence]

Originally Posted by Rev Jules

My son is having trouble tracing a faulty ABS Sensor for an MOT test, what should he look for.

Cheers.

Rev

If he has a car with cruise control, and both the cruise control and his speedo work, then the fronts must be ok. Its not too difficult then to check/replace the rears, using the methods described. The best advice i could give would be to buy only genuine oem sensors. You can get lucky with aftermarket ones, but i wasnt. Wasted a lot of time fiddling with one, eventually replaced again with oem and worked straight away.

[Avulon]

Originally Posted by David Lawrence

If he has a car with cruise control, and both the cruise control and his speedo work, then the fronts must be ok. Its not too difficult then to check/replace the rears, using the methods described. The best advice i could give would be to buy only genuine oem sensors. You can get lucky with aftermarket ones, but i wasnt. Wasted a lot of time fiddling with one, eventually replaced again with oem and worked straight away.

Thanks David. A very good point that - the speedo works off the Driver side (RH) front wheel and I believe (strangely enough because one would just expect it to use the speedo reading) the cruise controls uses the passenger side (LH) front wheel.


I should also add that especially with the rear sensors that it's known for rust flakes from the brake backplate to get between the sensor and bearing face and cause issues - sometimes just cleaning things up gets it working again.