My wife was using my 991 today. She was using the nav and radio and all was working. She stopped to run an errand, got back in and the PCM was totally dead. It won't power on at all - no phone, no radio, no navigation. The screen is black. When I flip through the menus in the instrument panel, the screens for radio, phone and navigation all say "radio off", "phone off" and "navigation off". Anyone have this happen? I've looked for a way to turn the system back on but it looks like a trip to the dealer is in my future.

 

She may have pushed the left PCM **** and held it. This turns the PCM completely off. When the car is running push the left **** again and release it. Hopefully this will turn it back on...

 

Thanks - we both tried that to no avail (She's had a Cayenne for the last 2 years and is better with PCM than me). I even tried holding the **** in for a minute seeing of it would force a reset - no such luck.

 

Fuse maybe?

 

Only two thing left that I can think to try before going to the dealer but likely low probability--- easy one, use the other key to start the car and see if the PCM comes on; a little more work-- pull one of the battery cables or the fuse for the PCM (I don't know if they are labeled) and then replace and see if the PCM comes on. And yes, PCrazy's idea of just checking the fuse is a good one.

 

Thanks for the suggestions. I am going to just stop by the dealer tomorrow morning on my drive in to work.

 

your first mistake was letting the mrs, drive your car. ARE U NUTS???

 

yes, better dealer check it vs. trouble shooting...good luck and keep us posted.

 

On the 997 cars the PCM would occasionally go blank if parked in an area with high technology or security interference . For instance parked in a garage in an area where there are banks wiped mine out once . I also noticed that in busy work hours the the PCM wiped out moreso than at night . Also once its wiped out the car has to be shut off and restarted but if still in the same area the problem might repeat itself .

 

This morning when I started the car I got some kind of low battery/power interuption message on the dash. The car started right up and the PCM was working again. I am baffled by the low battery thing. The car is not a garage queen and I drive it several days a week - including all day on Saturday. Yesterday when the PCM died, my wife had been out driving the car for a hour, turned it off to stop to provide assistance after witnessing a bike accident and when she got back in and restarted it a few minutes later, the system was dead.

I put a call into the service manager at my dealer.

 

My next Porsche gets ordered without PCM...so may have to be a Cayman

 

apologies for reviving this old thread ...

@caveatesq ... did you eventually figure out what was wrong ? i have a 2014 Cayman PDK with PCM 3.0 ... and its doing something similar to what your cars doing ... i can start up and drive the car 30 times with no pcm issues ... and then randomly it will not come on when i start the car up ... it only occurs on start up and very random ... but what i noticed is that when it does do it, switching off and turning on again does not help ... its almost like i need to wait for it to work again ... if i pull a fuse out and replace the fuse then its all ok again ... battery voltage is 13.5V - 14.7V (stationery to driving)

 

I charged the car's battery fully and it never happened again.

 

+100

 

thanks caveatesq ... will get Porsche to check the battery for me ... BTW when the car is switched on and idling with no load besides the pcm being on ... what voltage is your battery voltage according to the cars MFD?