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Mike Noc · 9th September 2020, 19:32

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 looking something like this:

If any gaps are in the same place each revolution then likely a damaged reluctor, and if in random places suspect the sensor.
Other common failure causes are cable damage to the sensors, flakes of corrosion interferring with the sensing, or corroded plug pins at the ABS modulator.

You connect the positive probe of the multimeter to the signal wire, and the negative to chassis earth:

I made up a cable from some old bell wire and a scrap ABS plug and socket to save pinning through the cable insulation. Here it is testing a hub prior to fitting:

9th September 2020, 19:32	#4
Mike Noc This is my second home Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009 Location: Hampshire Posts: 11,550 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	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 looking something like this: If any gaps are in the same place each revolution then likely a damaged reluctor, and if in random places suspect the sensor. Other common failure causes are cable damage to the sensors, flakes of corrosion interferring with the sensing, or corroded plug pins at the ABS modulator. You connect the positive probe of the multimeter to the signal wire, and the negative to chassis earth: I made up a cable from some old bell wire and a scrap ABS plug and socket to save pinning through the cable insulation. Here it is testing a hub prior to fitting: Last edited by Mike Noc; 9th September 2020 at 19:36..