Hi

I have a strange fault with my PCM unit in my '04 Cayenne. About 6 months ago the radio reception went and then I noticed that the brightness on the screen had dropped, I had the radio ariel check with a confirmed working unit but still the same.

I had decided to change the headunit and then randomly last night the radio reception and the brightness returned to normal and all was working fine. This morning all still fine and then whilst driving it went again.

Any ideas if this is a PCM unit fault or may be a loose connection somewhere.

Thanks

Tan

 

Hard pin down at this point, historically PCMs have mostly been reliable but there have been failures. Intermittent failures you describe are not that common so I would suspect some circuit board issue like a dry joint. Take it out and put it back next time it happens to see if movement has any impact.

otherwise prepare to replace

 

This reminds me of GM's move to lead-free solder in all Delco-Remy radio products back in the '80's. As mudman said, loose solder joint likely the culprit. Nothing like a trained hand slap to the side of the console to see if the problem comes back... ;-)

 

The initial fault developed last winter after the rear washer tube came off, so I was wondering if the fault / connection issue is at that end (rear of car) or actually in the PCM itself?

 

If the antenna booster got doused with washer fluid, your problem may lie there. However, this doesn't explain why your display unit dims. Water and electricity definitely don't mix well. Hopefully, nothing shorted.

Try swapping your antenna booster with a working unit bearing the same part number, as there have been several production variants since 2004.