All,

The ABS light is coming on and staying on if I reverse the car? It won't come on if I drive forward first? Could this be a dirty sensor?

Thanks.
Alan.

 

Yes quite possible.

The rear sensors are inside the drum/disc,any rust or metal cant escape and atach themselves to the sensor (magnetic) this gives an inacurate reading to the ABS ecu so you will get a light coming on.Do you get a juddering brake pedal at low speeds?

On the other hand,one of the sensors might be buggered.

I would clean all the sensors,with brake cleaner, before anything else.

You can use a multimeter to test the sensor.A duff sensor will give you an open circuit reading when its shot.

I can help with a sensor if you need one.