Finding that mystery fault.

[backtothe80s]

98 Volvo V70.

No fault codes or lights. ABS randomly kept kicking in the other week at low speeds with the pump clicking.

Got it recovered to the Volvo specialist. Road tested fine. Did not repeat the fault. No damage to the rings, sensors etc.

Drive home absolutely fine. They did mention it could be the OSF sensor stating to go but tested ok. Nothing needed doing.

Any experiences? Bit reluctant to press her back in to daily duties.

I know the solder joints on the module can go bad but there's no lights or issues symptoms to a bad module.

Anyone else experienced this? Not specifically Volvo just in general?

[astranaut]

My brothers e39 had this fault, it was either a cracked ring or the pad wear sensor at fault, I cant remember which. It did it all the time though not intermittent.

[homersimpson]

The only time i've ever seen this on an ABS system (kicking in at low speeds) is when there is a crack in the sensor ring which makes the gap between two of the teeth ever so slightly wider than the others, at high speeds the car doesn't see the difference but at slow speeds it can pick it up and cause the ABS to kick in as you come to a stop.

Sometimes it takes a bit of looking to find the crack.

[mk2cossie]

Jan 15, 2021 23:19:38 GMT homersimpson said:

The only time i've ever seen this on an ABS system (kicking in at low speeds) is when there is a crack in the sensor ring which makes the gap between two of the teeth ever so slightly wider than the others, at high speeds the car doesn't see the difference but at slow speeds it can pick it up and cause the ABS to kick in as you come to a stop.

Sometimes it takes a bit of looking to find the crack.

Definitely this! Had loads come in to work of various manufacturers, and the cracked reluctor ring is the most common cause of the faults described

[backtothe80s]

Update.

I've put 3-400 miles on the Volv now and aside from when it's first trip out of the car park it hasn't repeated.

It was being sat for a week or so at a time so may be something to do with lack of use? Baffled.

Starting to gain a bit if trust back in the brakes...!