ABS issue only when cold - ideas please

[JMC 0]

On my G60 (so very limited VagCOM) the ABS has recently started playing up, but only when cold. When cold the light comes on and stays on. Then once it has been driven (typically for 10-20 miles), if I switch her off and start her up again the ABS light goes out as normal. Then if the car sits for a couple of hours and cools down again, the ABS light comes on again. First things that come to mind are ABS pump plug, take off, clean and WD40, and the relay to make sure the contacts are ok. Any other ideas welcome (could it be to do with the spacing between the sensors and the slotted disks/drums on the wheels changing with temp for example)?

[seanl82 23]

Give the sensors and reluctor rings a good clean before anything else, see how you get on. Intermittent ABS faults usually point to those mate.

[robdriver 10]

I had the same issue and it turned out to be one of the rear wheel speed sensors.. the cold increases the restistance which sets off the warning lamp

Get a printout from VAG when lamp is on and if it show a rear speed sensor (like mine) get one on FleaBay to seventeen pounds....it was a perfect part with same connectors and fittings.....problem now fixed

[JMC 0]

Cheers for the ideas guys - it does definitely seem to be temp related, so will see what happens if we (ever) get a warm day as well.

[James. 9]

Test the resistance on the sensor with a multimeter. A reading of 1 is about right.

[ChrisL 18]

Sorry to Hijack the thread but I have my rear sensors off the car and with a multi-meter set on the 2k ohms setting I get 1.1 for both sensors, do these seem OK? should the reading chamge much if I move the sensor ring closer to the sensor?

[James. 9]

That seems fine Chris. There's usually an issue if the sensor reads zero or the numbers bounce around wildly.