ABS Sensor fault

Hi everybody,
the ABS warning light has come on and the diagnostics are saying front left senor faulty. I changed it but the light is still on and the diagnostics wont clear the fault. Ive tested the sensor I took out and the one I replced it with and Im getting about 600 Ohms on both which I think should be ok. To go further I wander if someone could clarify some things:

1) When Lexia says left side does it mean gearbox or cambelt side? I thought its the gearbox side but it would explain a lot if left is the cambelt side, lol.
2) The ABS light aluminates as soon after the car starts and before you move, does that suggest anything to anyone?
3) Im guessing once the fault is fixed the fault will clear itself, and Lexia wont clear a persistant fault?
4) Im guessing its unlikely to be the Bearing Encoder as that would only register as a fault after the car moved?
5) I do have a worn left tyre, but Im guessing its unlikely to be that as that would only register as a fault after the car moved to?

any help appreciated,

cvloenen wrote: ↑Thu Feb 27, 2020 8:26 pm Hi everybody,
the ABS warning light has come on and the diagnostics are saying front left senor faulty. I changed it but the light is still on and the diagnostics wont clear the fault. Ive tested the sensor I took out and the one I replced it with and Im getting about 600 Ohms on both which I think should be ok. To go further I wander if someone could clarify some things:

1) When Lexia says left side does it mean gearbox or cambelt side? I thought its the gearbox side but it would explain a lot if left is the cambelt side, lol.
2) The ABS light aluminates as soon after the car starts and before you move, does that suggest anything to anyone?
3) Im guessing once the fault is fixed the fault will clear itself, and Lexia wont clear a persistant fault?
4) Im guessing its unlikely to be the Bearing Encoder as that would only register as a fault after the car moved?
5) I do have a worn left tyre, but Im guessing its unlikely to be that as that would only register as a fault after the car moved to?

any help appreciated,

Hi

2) suggests that there is a short or open circuit to the sensor, or there is an internal ABS ECU fault (lexia will tell you)
3) lexia can't clear persistent faults because they need to be repaired before clearing. temporary faults, by their nature have repaired themselves.
4)Yes, it sounds like part of the boot-up self diagnostics of the ABS ECU, to test all inputs for a sane state.
5)Yes, also the ABS ECU is designed to factor in mismatched tyres, it is really looking for a locked-up wheel.

C3driver52 wrote: ↑Thu Feb 27, 2020 8:52 pm

cvloenen wrote: ↑Thu Feb 27, 2020 8:26 pm Hi everybody,
the ABS warning light has come on and the diagnostics are saying front left senor faulty. I changed it but the light is still on and the diagnostics wont clear the fault. Ive tested the sensor I took out and the one I replced it with and Im getting about 600 Ohms on both which I think should be ok. To go further I wander if someone could clarify some things:

1) When Lexia says left side does it mean gearbox or cambelt side? I thought its the gearbox side but it would explain a lot if left is the cambelt side, lol.
2) The ABS light aluminates as soon after the car starts and before you move, does that suggest anything to anyone?
3) Im guessing once the fault is fixed the fault will clear itself, and Lexia wont clear a persistant fault?
4) Im guessing its unlikely to be the Bearing Encoder as that would only register as a fault after the car moved?
5) I do have a worn left tyre, but Im guessing its unlikely to be that as that would only register as a fault after the car moved to?

any help appreciated,

Hi

2) suggests that there is a short or open circuit to the sensor, or there is an internal ABS ECU fault (lexia will tell you)
3) lexia can't clear persistent faults because they need to be repaired before clearing. temporary faults, by their nature have repaired themselves.
4)Yes, it sounds like part of the boot-up self diagnostics of the ABS ECU, to test all inputs for a sane state.
5)Yes, also the ABS ECU is designed to factor in mismatched tyres, it is really looking for a locked-up wheel.

Another possibility is a corroded or broken ABS ring.

Hi,
can someone verify which side of the car Lexia refers to when it says left side, Gearbox or cambelt side? This would be good know for sure and confirm Im looking at the right side.

I would have though broken or corroded ABS ring would only set of a fault once the car is in motion? As the ABS light is coming on before motion I would think the rings are not the problem.
Does anyone know if theres a voltage I can check reaching the wheel senor? Im thinking that the wiring behind the sensors connection under the wheel arch is fauting somewhere. It looks like to access plugs in the enginge bay you probably have to remove the battery box, would that be correct?

cvloenen wrote: ↑Fri Feb 28, 2020 11:56 am Hi,
can someone verify which side of the car Lexia refers to when it says left side, Gearbox or cambelt side? This would be good know for sure and confirm Im looking at the right side.

I would have though broken or corroded ABS ring would only set of a fault once the car is in motion? As the ABS light is coming on before motion I would think the rings are not the problem.
Does anyone know if theres a voltage I can check reaching the wheel senor? Im thinking that the wiring behind the sensors connection under the wheel arch is fauting somewhere. It looks like to access plugs in the enginge bay you probably have to remove the battery box, would that be correct?

Unfortunately it doesn't. I've had this twice on rear brakes. On both occasions, there were permanent ABS fault and ESP faults on start-up without the car moving.

Unfortunately it doesn't. I've had this twice on rear brakes. On both occasions, there were permanent ABS fault and ESP faults on start-up without the car moving.
[/quote]

When you had this problem what fault did Lexia suggest?


Can Lexia differentiate between a faulty sensor, a slower spinning wheel or a non spinning wheel? Or would fault always be " ABS sensor"?

cvloenen wrote: ↑Sat Feb 29, 2020 6:09 pm Unfortunately it doesn't. I've had this twice on rear brakes. On both occasions, there were permanent ABS fault and ESP faults on start-up without the car moving.

When you had this problem what fault did Lexia suggest?


Can Lexia differentiate between a faulty sensor, a slower spinning wheel or a non spinning wheel? Or would fault always be " ABS sensor"?
[/quote]

I don't know as I ook it to a garage; replaced the rotor and all was well.

Well i now have the recirculation pump permanent fault! checked wheel sensors and their all ok. so Im looking in to getting a replacement ABS module.
I have the MK60, they seem to be hard to find second hand but I can get my hands on plenty MK70's

Has anybody tried putting the MK70 Module on the MK60 ECU ?
Ive also read that if you use a different ABS ECU it needs to be programmed in to main ECU and only citroen can do this, is this true or will it self learn? anybody tried this? Just wandering if I could just put the complete MK70 on my car and it would go no probs?
thanks Ian

So you are going to try and split the ECU(s) from the hydraulic block(s) and recycle your old ECU. Interesting.

The ECUs need to be configured with stuff like wheel diameter, if it's brand new. If you are going from C3 to C3 it wont need configuring, it's already been done. If it came from a completely different vehicle it might need re-configuring.

I don't know but I would say that different revisions of ABS units would be compatible. To my knowledge it's only the ESP units that are not compatible with non-ESP systems.

Ozvtr wrote: ↑Mon Mar 09, 2020 6:08 am So you are going to try and split the ECU(s) from the hydraulic block(s) and recycle your old ECU. Interesting.

The ECUs need to be configured with stuff like wheel diameter, if it's brand new. If you are going from C3 to C3 it wont need configuring, it's already been done. If it came from a completely different vehicle it might need re-configuring.

I don't know but I would say that different revisions of ABS units would be compatible. To my knowledge it's only the ESP units that are not compatible with non-ESP systems.

Thanks, theres very helpful.
I managed to contact a Company refurbishing ABS units and got some information. According to them MK60 & MK70 are not compatible. One differenece being one has an internal pressure sensor and the other external. Anyway, I have managed to source a second hand MK60 Unit at good price, so hears hoping that will solve all.