This one's strange. I 've had the 04 545i for about 3 months, the PDC always gave the flashing PDC malfunction error. At the dealer , they said I need a new front bumper PDC harness and that someone had painted the front bumper and the sensors, that maybe sanding off the paint would work but they wouldn't do it. Total for a new harness and labor $1200.00 US. So I went ahead and sanded the sensors, no difference. Then one morning I started the car and viola! The PDC was working, but by lunch time no more PDC. It has happened several more times and it seems to be right after there is a strong rain storm they start to work. This morning they weren't working , went out at lunch right after a short but somwwhat strong rain shower and bam! Its on!. Washing the car doesn't do it. I live in South Florida, its always humid, could it be a contact problem? Anybody ever heard or seen this? really wierd. Thanks guys!

 

Is that an old E34 speedo in your sig? or is it a E36? I cant make it out...

 

Probably a connection/corrosion problem. When the connection gets wet, it conducts. It probably is in the harness. I'd be looking in a junkyard for a used harness or fixing it myself using an ohmmeter after having a second pair of helping hands to remove the bumper. I once fixed an intermittent front fog light on my E46 by cleaning up the corrosion due to a crack in the housing. I fixed the housing by wrapping it with duct tape. Worked like a charm.

 

Isn't duct tape an amazing solution to everything ?