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Bill, Technician
Category: UK Ford
Satisfied Customers: 3307
Experience:  City & Guilds
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ABS warning light stays on

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ABS warning light stays on
Good evening, I hope I can help you.

When you were told it was the sensor at fault, what you should have been told was that the signal from the osr sensor was incorrect.

The next stage would then have been to measure the resisance of the sensor, then for a short or open circuit in the sensor, then its ability to produce an ac voltage signal, the condition of the reluctor wheel at the hub, the continuity of the wiring between the sensor plug and the ecu and then determining the fault dependant on the results of those tests.

Just because a fault code says sensor fault it doesn't mean the sensor is at fault. It only means there is something wrong with its signal when compared to the others. It then has to be investigated properly to determine fault.

My name is XXXXX XXXXX if you need further help, just ask.
Customer: replied 7 years ago.
Thanks for your help with that Bill

I am no Mechanic, but i am fairly switched on, is there anything i can do, eg remove wheel, do a voltage test on the sensor (i have a multimeter), clean part of the wheel etc?


You need a multimeter that can read ac voltage and ohms.

Disconnect sensor at wheel hub and probe the two pins. It should be about 1000 ohms.

Now check one pin and earth the multimeter cable and you should get infinite ohms or OL on display.

Next probe both pins again and switch meter to acv. Spin wheel at approx 60rpm and voltage should be about 0.5acv. The faster you spin the wheel the higher the voltage. Do all these checks at all wheels. The readings should all be similar.

Next is to check the reluctor ring and the airgap bewteen it and the sensor. Check for missing, broken, damaged teeth etc.

If all these check out ok then yo have to disconnect the plug at the ecu and carry out the same tests at the pins concerned. If all the readings are still the same then it means all the wiring is ok and fault is with ecu.

If the readings are different then you have wiring fault through car.

Customer: replied 7 years ago.
Spot On, Thanks for that, i will of course accept your answer, but one last question. Where is the ecu?
It's intigrated with the ABS modulator under the bonnet.

Bill and 2 other UK Ford Specialists are ready to help you
Customer: replied 7 years ago.
Thanks for all your help Bill.

Warm Regards

Chris Rowell
No problem mate.

If you can leave me feedback also its much appreciated.