Possible causes, elimination, notes: Elimination:

Delete fault memory, disengage reverse gear and switch off ignition.

Then switch on ignition, engage reverse gear again and read out fault memory.

If the fault reappears, check plug on sensor for open circuit.

If there is no open circuit, check for continuity with an ohmmeter from sensor connector pin 1 to pin 4 and pin 1 to pin 2. Continuity should not be measured.

If no short circuit can be detected, replace sensor.