ABS sensor?
 

Hi all, just a quick question, is there an easy way of determining the abs fault without being able to plug it in to a T4? Since I had new trailing arm bushes fitted last year, the abs light has been on. The driver side rear has a newish back plate and sensor, so was assuming it was probably the passenger side rear, but as it’s a pain to do, I’m hoping there’s a way of finding out before going all through changing it, only to find it was the other side.

Cheers.

Can’t think of anything easier than plugging it into TOAF, takes less than 5 minutes including the walk to the garage.

Of course it won’t tell you if it’s the bearing or sensor but will tell you which corner.

Regards

Courtesy of French Mike you can check all the ABS sensors and magnetic reluctors in the wheel bearings using a voltmeter.

The signal voltage changes from 1.7V to 0.7V as each magnetic segment passes the sensor, so jack each wheel in turn and slowly rotate it marking the switch points on the tyre wall with chalk. You should end up with 48 chalk marks.

If any gaps are in the same place each revolution then likely a damaged reluctor, and if in random places suspect the sensor or possibly a slightly too big air gap.

Other common failure causes are cable damage to the sensors, a build up of corrosion on the backplate of the rear wheels, or corroded plug pins at the ABS modulator.

Here is a front hub being tested prior to fitting. I use an extension cable made up from some old speaker wire and ABS plug and socket which saves pinning through the ABS cables. It also doubles up to allow any sensor to be plugged in to the OSF so that the speedometer can be used as a diagnostic.

https://i.imgur.com/W0VviKD.jpg?1

Thanks, I’ve had an offer of a local T4 to check which it is, so will hopefully be using that, but if not I’ll have to dig out the multimeter.

Cheers.