Dear Mr. Weekend,

Hope you're well. I concur with jimo: the sensor - located on the underbody, inboard of the driver's headlight - likely has failed. It is Volvo Part #1347010: MSRP is around $35.00.

The sensor's two tubular electrical contacts may be corrosion-bonded to the the wiring harness connector's terminals. That might account for the malfunction. Corrosion is likely to frustrate separation of the sensor from its wiring harness.

It might be easier to get a replacement at a salvage yard. This sensor was used on C/S/V70s (all years), 850s (all years), 960s (all years). If the part comes from afar - or if the yard doesn't allow you to remove the sensor - ask that the donor car's sensor wiring harness be cut so as to leave you six inches (150mm) of wire. You can then splice the replacement sensor to your car's wiring harness.

If you want to remove your car's sensor, saturate the connector with DeOxit or a similar corrosion-dissolver. Allow DeOxit time to work: the electrical contacts fit tightly. It will take time for DeOxit to work its way through micro-channels in the corrosion. Even then, separation of the wiring contacts is delicate work.

If DeOxit does not restore the sensor to proper operation, saturate the wiring connector with PB Blaster or similar penetrating oil (e.g., Kroil). A penetrating oil will lubricate the contacts - free of corrosion - and ease removal.

Hope this helps.

Yours faithfully,

Spook