[MattTPE46]

The below opinions are based on my experience from my E39, which should be similar, as I have not had any problems with my E46.

If a sensor fails then when you engage reverse you get a continuous tone.

Sensor failure is most common followed by wiring/connectors.

If not that then possibly the module.

Hooking up the car to a laptop with diagnostic is the best way to trouble shoot. You can see a the faults on the system and run tests.

Replacement sensors from BMW are very expensive. On ebay they are cheap but some are good and some not so. I know which ones to buy on UK ebay but that won't be any use to you so others may be able to recommend.

Yo can you give me the link ? people say ebay sensors only work on the 2 middle i brought one from there and my pdc still not working