Pesky Sierra Cosworth ABS fault
Discussion
Can anyone assist with a Cossy ABS fault that's proving difficult to fix ?
Symptoms are ABS light comes on and extinguishes as expected when engine is started. As soon as you start to move, ABS light comes back on. ABS doesn't work.
Have checked at the ABS ECU for waveforms from each wheel sensor, all four are present, impedance across each sensor is the same few ohms. Have swapped ECU, albeit with a used one, and same fault persists.
If you jack up the back wheels and put in gear, light doesn't come on.
Sensors look OK, and hub reluctor rings are in place, no teeth missing etc..
Ford workshop manual is of no use, no diagnostics info. We're all now a bit stumped. Does anyone have any suggestions or advice ?
All help much appreciated.
Symptoms are ABS light comes on and extinguishes as expected when engine is started. As soon as you start to move, ABS light comes back on. ABS doesn't work.
Have checked at the ABS ECU for waveforms from each wheel sensor, all four are present, impedance across each sensor is the same few ohms. Have swapped ECU, albeit with a used one, and same fault persists.
If you jack up the back wheels and put in gear, light doesn't come on.
Sensors look OK, and hub reluctor rings are in place, no teeth missing etc..
Ford workshop manual is of no use, no diagnostics info. We're all now a bit stumped. Does anyone have any suggestions or advice ?
All help much appreciated.
Which cosworth is it??
Sierra 2wd 4wd or escort?
My first suspicion would be either relucter ring (I see you have checked) but have you made sure they are secure the gaps to sensors are all equal & there is no play in bearings??Could be gearbox speed sensor fault, if it's a Sierra the connection to the ecu can be an issue that causes all sorts of problems & is normally cured by disconnecting overnight.
Sierra 2wd 4wd or escort?
My first suspicion would be either relucter ring (I see you have checked) but have you made sure they are secure the gaps to sensors are all equal & there is no play in bearings??Could be gearbox speed sensor fault, if it's a Sierra the connection to the ecu can be an issue that causes all sorts of problems & is normally cured by disconnecting overnight.
theshrew said:
Do the exciter ring teeth have any corrosion on them ? are the sensors close enough maybe you have a signal but the peaks and troffs are not big enough ?
Sounds like you have checked most things tbh and the above wont help much but its worth checking.
I think it has to be something like this. I'll take both front sensors out, clean the ring and make sure no teeth missing etc. Another search showed up someone with minor voltage difference between the fronts was causing same fault. New sensor fixed it. Thanks for the tip, I have spent hours on this with no resolution, so all suggestions welcome.Sounds like you have checked most things tbh and the above wont help much but its worth checking.
neiljohnson said:
Which cosworth is it??
Sierra 2wd 4wd or escort?
My first suspicion would be either relucter ring (I see you have checked) but have you made sure they are secure the gaps to sensors are all equal & there is no play in bearings??Could be gearbox speed sensor fault, if it's a Sierra the connection to the ecu can be an issue that causes all sorts of problems & is normally cured by disconnecting overnight.
It's a 3 door sierra. No play in front bearings, but as above on another search there was a comment about grease from the bearing or CV clagging it up and causing intermittent ABS issues.Sierra 2wd 4wd or escort?
My first suspicion would be either relucter ring (I see you have checked) but have you made sure they are secure the gaps to sensors are all equal & there is no play in bearings??Could be gearbox speed sensor fault, if it's a Sierra the connection to the ecu can be an issue that causes all sorts of problems & is normally cured by disconnecting overnight.
Didn't realise there was a gearbox sensor.. will have to look at the wiring diagrams again... The thing regularly sits for weeks with the battery off, this fault came up last summer, the car is not used much and is garaged. The MOT ran out in October, I now need to re-tax and need to MOT it. I think I'll have to SORN in the meantime, as have other more pressing car issues to deal with.
Its worth checking the gearbox sensor yes but i dont think that will be your issue.
You say that the light doesnt come on if the back end is jacked up ( presume you tested that while in gear driving above the speed for the abs to work ) If so then surely that points to the problem being on the front end or how the ecu is reading the signals from the front end.
You say that the light doesnt come on if the back end is jacked up ( presume you tested that while in gear driving above the speed for the abs to work ) If so then surely that points to the problem being on the front end or how the ecu is reading the signals from the front end.
There is no gearbox sensor on the ate teves abs system on a 3dr.
The common fault is usually the connections into the brake fluid container and the ones to the pump, these get corrosion inside due to their location in the engine bay. Wiggle off, clean out spray with electrical spray (not WD40). Next place to look is the connector from each wheel sensor into the loom. At the front these are located on the inner wing and are round, its rarely the rears though as the connectors are in the dry under the rear seats. If removing them the sensors themselves often fuse into the hubs and are a pita to get out.
Cheap tip, the system uses the same wheel sensors from a mk3 granada. Buttons from you local breaker, mention the word Cosworth and they become £100 each secondhand.
Rarely anything inside the car related to the ABS system goes wrong, its nearly always parts open to the elements.
The common fault is usually the connections into the brake fluid container and the ones to the pump, these get corrosion inside due to their location in the engine bay. Wiggle off, clean out spray with electrical spray (not WD40). Next place to look is the connector from each wheel sensor into the loom. At the front these are located on the inner wing and are round, its rarely the rears though as the connectors are in the dry under the rear seats. If removing them the sensors themselves often fuse into the hubs and are a pita to get out.
Cheap tip, the system uses the same wheel sensors from a mk3 granada. Buttons from you local breaker, mention the word Cosworth and they become £100 each secondhand.
Rarely anything inside the car related to the ABS system goes wrong, its nearly always parts open to the elements.
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