Parking sensor fault after MOT

[faddy]

Had my C5 X7 MOT'd today at Halfords (I know, I know, but the test was free) and the first time I reversed after collecting the car the parking sensors were in fault mode (exclamation mark and four bars on the display, and continuous tone). Anything obvious that they might have inadvertently disconnected during the test?

[faddy]

I'm now desperately trying to remember whether I heard anything from the sensors when parking, forwards, at Halfords. I suspect I may not have done which would rather let them off the hook.

[GiveMeABreak]

If you have one sensor out it can affect the the whole system.

If you have a Lexia, connect up and run a global test and it will tell you which sensors are faulty (or whether there is another fault).

Before I tell you the manual test, I suggest you go into the boot and check you have not had any liquid spills of any sort! Lift the boot mat and check the unit to the right of the spare tyre that is mounted thereabouts. 5 Litres of Halfords screenwash decided it was going to leak and emptied itself in my boot - happened to be purple blackberry smelling stuff - but ended up soaking the ECU. Took me a week to dry the boot and the ECU out and a lot of electrical cleaner!

If all is well there, then with the ignition on, put the car into first gear and go round each front sensor in turn and very gently place your finger near to the sensor - if it is operating, you will feel a very slight tingle. Repeat for the others and then put the car in reverse and repeat. Any sensors that aren't giving a slight 'pulse' will be duff and probably the cause. This can be due to water getting splashed up the sensor cables and then running back down into the sensor plug and corroding the contacts.