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Hi All,

Having a few problems with my '09 R56 Cooper S and not sure where to start from based on my initial diagnosis, looking for any thoughts what to try first. :nerd:

Problems / Errors experienced:
Intermittent - The DSC / ABS / TMP system lights (Systems disabled, drive moderately etc).
Intermittent - 5D8D - DSC wheel speed sensor, signal, front right, high
Intermittent - 5E11 - DSC wheel speed sensor, signal, front right, voltage range
Intermittent - 2FF6 - DME - Vehicle Speed Signal
Very Rare - Multimedia system restart (twice so far in probably 4-5 months) - No error messages associated with it.

Thoughts/Observation (Diagnosis):
1.) Wheel speed sensor on it's way out. It seems the front right sensor registers 255 km/h on occasions but I can't figure out exactly when as it's intermittent. BUT there seems to be a correlation between low battery levels / start/stop traffic and the problematic sensor.
2.) Due to this correlation, I thought perhaps it's the battery or alternator causing the issue. Battery is a Bosch AGM battery which was only changed last year so I doubt it's that. Volts across battery are around 12.4-12.6V when engine is off and around 13.5V-14.6V when engine is on indicating alternator is probably still working okay. On load test (All electrical components on incl heated seats, windscreens etc) at idle, volts drop to just under 13V, which could indicate an alternator issue on the other hand, I'm not sure the load I put was a lot to ask from the alternator at idle.
3.) This morning I was sitting in the car talking on the phone over bluetooth, engine off and monitoring the battery volts through the ECU. They started at 12.6V and slowly dropped to 12.2V (reasonable as I was on the bluetooth) but then they suddenly dropped to 0.4V and immediately the wheel sensor issue came up. I continued the teleconference for about 10 minutes and then started the engine, the battery gave me no problems and car started first time. Wheel speed sensor continued showing 255 km/h and then after an engine start cycle it dissapeared.

So given the above, not sure what to look into first other than just checking the connections are clean, change the speed sensor or alternator? On the other hand could it be the ABS module? Do you have any further tests to recommend?


Cheers,
Chris
 

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It seems the front right sensor registers 255 km/h on occasions ????? thats 158 mph nope you would struggle to get all 4 to do that lol. can use a multimeter set to mirco volts as all the abs sensors are a electric generator,, so by turn the road wheel ie on a jack wheel off road you will receive a voltage for the same amount of force on all 4 sensors,, ie restate wheel read it then read another one at same speed,, or could jack car up run in 1st gear on idle read the sensor outputs, they should all be the same,,
something like autocom cdp plus diagnostics os handy will help diagnose the system cab buy them on ebay £40 ish good tool for money p-codes
 
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