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I had a big lock up at a Club Track Day on Saturday.

The ABS light was on and no codes were read with a reader, fluid level was on the high mark. Resetting the ECU by disconnecting the battery also failed to clear the ABS light.

Luckily I had Daniel Deckers on hand to offer advice which was, clean the rear ABS sensors.

This is a very easy job. The rear sensor is held in position by one 10mm bolt on the rear hub.
Undo the bolt, pull out the sensor, it’s magnetised, check for metal filings standing out from the sensor.
If the filings are there, grab a cloth and wipe/pinch them off. Reassemble. Job done.

The front sensor is on the inside face of the hub and doesn't seam to be made from the same magnetised material but a check once in a while would still be a good idea.

It’s probably worth while checking the sensors at every pad change. It has taken 160,000 kilometres for this problem to occur on my car but it’s not fun flat spotting V70A’s. They’re not cheap.

That's for the heads up

ahh yeah the fuzz on the sensor. when I do coilover install on mine of other cars I clean the sensor

Just a quick follow up on my original post.

After cleaning all the sensors the problem reared its head a week later with the ABS light coming on intermittently.

I pulled all the sensors out again to check they were still clean, which they were and refitted them. The ABS light then stayed on permanently. So I went and bought a multimeter, something that I’d been meaning to do for a long time, to check the sensors. They all read the same zero resistance.

A quick phone call to Chris Gough revealed that the ABS module rarely fails and it’s probably a sensor. A bit of reading on the subject indicated that the only way to check is to rotate the wheel while reading the meter or connect the system to a diagnostic reader. YouTube has a bit of information on this.

I decided it was easier to find a workshop with a reader to check not only the sensors but the ABS module, as parts were expensive if I made a wrong call on which part I needed. (ABS module $450 second hand!!)

It took some time to find a workshop that would just do the test without wanting to do the repair job. In the end ABS at Kirrawee carried out the test ($130) and gave me the print out which indicated the right rear sensor was the problem.

Another phone call to Chris resulted in a second hand sensor being put in the post that day and into the car the following day, problem solved. Thanks Chris for the fantastic service and advice.

My ABS problems are having more come backs than Dame Nellie Melba!!!

The saga continues.

The latest has been the ABS kicking in on light brake application at low speed in the dry plus the ABS light coming on for no apparent reason.
Again I turned to Chris Gough, the master of all NC problems. He decided that it couldn’t be another sensor cable but rather a variable reading coming from the front magnetic hub ring, as the ABS light would come on with no brake pedal application. The rear hubs have a toothed ring so that ruled them out.

Chris said that the magnetic coating on the hub ring can crack or crazy, similar to rotors, or the coating be of variable depth, and this would give a false reading to the sensors triggering the ABS. He has seen this happen in high kilometre NC’s before.

So I removed the sensors and armed with a torch checked the ring but all looked fine, so I cleaned them up with some metho, reassembled and tested the system to find no change.

Back to Chris, this time I mentioned that I’d replaced the front left hub with an aftermarket one back in May. Chris indicated that maybe the magnetic ring was out of tolerance with the Mazda spec and the only way to fix it was replace the hub.

So to test the theory on the weekend I removed the “new” hub and refitted my old one. Two days later and the ABS is working fine (can't say the same about the hub bearing), so I have dropped the supplier of the aftermarket hub a note and hopefully will be supplied a new one under warranty.

All fixed? Only time will tell.

Finally determined my ABS problem. The aftermarket hub’s ABS ring is faulty. Refitting my old hub resulted in the ABS problem going away.

Another hub was sent by the supplier under warranty, but that’s another unfolding unfinished story.

Glad you got that sorted. So, only use OEM hubs if replacement is necessary?

I had a similar issue on my Clio.
The fix for me was to just swap the abs ring from the old worn rotor onto the aftermarket one as the aftermarket one just caused abs issues.
The rings are on the brake rotor and bearing.

I have not seen a NC ABS ring, I assume it is not removable in the same way??

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