Hi,
After getting new tyres fitted on my fiat punto (2006), and the allignment checked and adjusted a fault plays up. The speedo stops working after having driven a few miles and several warning lights pop up (esp, pas, engine warning and some others). I have checked for faults using the OBD port and cleared all codes, but the P0500 indicating a faulty vehicle speed sensor 'A' reappears.
having sensors on all 4 wheels i assume it has ABS.
I came across some threads with similar issues, but they all concerned non ABS cars, where the VSS is in the gearbox, but a ABS car uses the sensors on the 4 corners. Is there any way I can check which one gives trouble? Issue is that the problem only appears after some driving, and not immidiately, and from the error code I can't see a specific sensor that gives trouble.
many thanks for the advise.

Hi (Who ?), and welcome on board !

the speed is computed from a sensor at the gearbox output (differential), as an absolute value; the 4 corners sensors provide the ABS ECU with info of the four wheels angular speed, combined with other signals (throttle, brake pedal, ...) it gives an estimation of what wheel is doing what under various circumstances. The resulting "average speed" is compared to the GB sensor to insure they match within certain margin, if not the system will throw an error flag.

My bet is the GB sensor, since you didn't get ABS fault and your speed stoped working ...

BRs, Bernie

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