abs problem

[roverbeast75]

a month ago my brake pedal started pulsating during low speed braking. abs light would come & go until one day it permanently stayed on. Whenever the light stays on the brake doesn't pulsate

scanned the car it said that both front sensors were faulty, replaced them both but the light still stays on

I replaced the sensors a second time but still no luck, light still stays on

anyone that has had this issue aswell?

[vitesse]

Originally Posted by roverbeast75

a month ago my brake pedal started pulsating during low speed braking. abs light would come & go until one day it permanently stayed on. Whenever the light stays on the brake doesn't pulsate

scanned the car it said that both sensors were faulty, replaced them both but the light still stays on

I replaced the sensors a second time but still no luck, light still stays on

anyone that has had this issue aswell?

Then if the sensors are ok (no guarantee) then the problem is probably the magnetic pick-up strip within the bearing(s), usually caused by a build up of rust from the back plates.

Regards

[Mike Noc]

The scanner isn't clever enough to tell you that a sensor has failed.

Which sensors did you change?

If you are handy with a multimeter you can check each wheel in turn by slowly rotating it and measuring the voltage from the sensor - it should switch between around 0.7V and 1.7V as each magnetic segment is passed.

[roverbeast75]

Scanner said the 2 front ones were bad so I changed the fronts .. twice

[ZedTeeT]

More likely to be one of the rears. You should check for rust and a build up general debris around the sensor area. Easy enough to do even if it's just to rule that known issue out.

[trikey]

It will be a rear wheel bearing.

[Mike Noc]

Originally Posted by roverbeast75

Scanner said the 2 front ones were bad so I changed the fronts .. twice

Like I said the scanners ain't that clever. I have had aftermarket sensors fail from the start though - reading twice the voltage and confusing the ABS modulator.


With the ABS system it is better to correctly diagnose the fault before changing anything, as it is easy to add faults.


As mentioned, you can check the voltage output from the sensor and then narrow the problem down. There should be 48 changes of voltage from 0.7V to 1.7V in one wheel revolution, so check each wheel in turn - you can mark the tyre with chalk at each voltage change.


If any gaps are in the same place then suspect the magnetic reluctor in the bearing, and if in random places then suspect the sensor, or with the rears, too big an air gap between the sensor and reluctor.


Other common failures 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 before fitting:

[Arctic]

and most likely the OS rear, don't know why but 95% times it is always that wheel bearing but do let us know the out come.

[roverbeast75]

Originally Posted by Arctic

and most likely the OS rear, don't know why but 95% times it is always that wheel bearing but do let us know the out come.

My car is left hand drive so which wheel bearing will it be?

[roverbeast75]

can someone explain to me how it can be one of the rear bearings? why does the computer tell me it's the 2 front sensors?