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ABS light issue, sensor replaced, voltage good

205 Views 9 Replies 3 Participants Last post by  Slimfastjohn, 
S
Hi people, I've searched the forums and not found an identical problem so looking for ideas...
My 2009 mk4 mondeo's ABS light is on. As the common fault seems to be a wheel speed sensor, after a bit of searching online, I checked I had voltage to all 4 sensors which I did so I replaced one of the rears. By this time, the handbrake light had also come on, but went off again after changing the sensor. Unfortunately the ABS light stayed on, so I replaced the other 3 sensors to rule them out.
Light still on so I bought a code reader, and that told me it was the right rear wheel. I cleared the code but it lit up again straight away without the wheels turning so quite sure it's not the bearing or tooth count that's the issue. I've checked the wires on that corner for continuity and they're fine from centre connection to wheel. What's my next step guys? Many thanks in advance for even a nudge in the right direction! 🙏🙏🙏
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TheAntman
Codes, codes, codes.
These cars have an on-board diagnostic system that is there to help you locate faults rather than firing up the parts cannon and throwing money at it.
The very first thing you should do is connect Forscan or similar and scan the car for codes. If the ABS light is on, then there will be ABS fault codes stored.
It may well be a defective sensor, but may also be something else entirely.
I had a similar issue on my Yank many years ago - Once I'd cleared the wheel sensor fault I discovered a corroded earth connection and once I'd sorted that, everything was fine.
I can't stress enough the importance of scanning for codes.
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S


Thanks for the reply The Antman, but where do I go from here please?
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PURPLE_2L_LX
Test not complete is because you reset the codes and have not driven long enough for them to reset.

You want the live data from each wheel sensor to see what data each wheel is giving. It maybe an intermittent
figure where all wheels match then suddenly one skips or drops out and then picks up again or it may start
off with no reading and then correct itself.

Live data would be useful.
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S
That makes sense. I'll have a look at doing it on my days off this week thanks 👍
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S
Ok so I've read again after some driving and just get this (see attached pic). If I run live data whilst driving, I
It doesn't seem to show any wheel speeds at all, so unsure if that's a software issue (as in, the app I'm using), or the ABS control module is knackered completely and simply not reading anything 🤷🏻‍♂️

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PURPLE_2L_LX
Will your device work with the Forscan app?
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S
I'll download the free app to check it's compatible, and pay for the proper one if it looks promising 🤷🏻‍♂️
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PURPLE_2L_LX
Yeah I think the free version only allows one sensor. I bought it with a google discount and it was cheaper
back then also so only paid £1 or £2.

The other option is the Windows version if you have a tablet or laptop. Free and more features.
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S
Doesn't seem to be compatible as it won't connect to it unfortunately 🤷🏻‍♂️
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