iammulva

Recently my radio (entire PCM) would not power on. I checked the footwell fuse that I thought was related to the radio but it was fine. I just found out where the 10a fuse on the back of the PCM is hiding. I replaced it with a new one and immediately smelled electrons. I pulled it and it was blown. I've searched for related issues on this forum and google. I cannot find anything that is helpful.

I have a Dension 500BT installed in the glove box which gets power from the passenger footwell lighter. I assume the Dension or the install is not the issue because the power is separate and it was working for several months prior to losing power in the PCM.

What more can I do to troubleshoot/fix this myself? Do I need to send my PCM to get repaired or should I buy a used one?

All input is appreciated.

jhbrennan

Even though it sounds as if you have eliminated the Dension as the problem, you might try disconnecting it entirely and see if the same thing happens.

iammulva

Roger that. i have to get a few more 10a fuses first.

iammulva

Unplugged power from Dension unit. Put 10a fuse in PCM. Blew immediately. Checked all other fuses. All good.

Time to ship it off to repair shop?

utkinpol

PCM is not cheap. New one will cost a lot.
It may be cheaper to install something aftermarket, like Pioneer of any other unit that fits and has matching casing for 997 cars.

Alan C.

A few guys on here have sold their PCM units. There is a great article on a switch to an iPad Mini. And as has been stated a new after market unit may be a better choice. It would certainly be better than the stock unit.

chris.hanle

Make sure you rule out all of the things that are controlled by that particular fuse. It is not always logical what is controlled. My fuse 10b kept blowing and my external cooling fans were on all the time. Turns out that fuse controlled external cooling fans (radiator fans)sport chrono, vent. seats, and a couple other things unrelated controls. Turns out it was a pinched ventilated seat wire. Good luck.

Minok

The fuse blowing indicates a short in the system.. could be something shorting out on the circuit board, or a failed component on a board, or a crushed wire. Unless debris or critters got in there, a failed component seems like the most likely candidate. You could do an inspection of the circuit boards in the PCM to look for the obvious signs of a problem (if you know electronics). Beyond that, replacing the PCM with a used PCM from another car (beware options hardwired to a PCM and authorized for your VIN # from Porsche)... get a new one from Porsche, or go 3rd party. If you don't have a lot of Porsche options (like navigation, voice control, embedded phone /bluetooth handsfree, etc) then going with an aftermarket system may be a good choice.

fskof

When you had the PCM pulled out did you inspect the wire harness for a pinched wire. Any bare wire that makes contact with metal can blow a fuse. I would check that before you spend $$$ on the repair shop. I hope its something simple and easy to fix.

iammulva

Thanks for the input. I will double check PCM wiring harness for integrity. Mixed feelings about all suggestions: iPad, aftermarket, used or new PCM. : (

iammulva

Double checked the wiring harness to the PCM. No obvious signs of damage or exposed wires. Harness was in good shape and proper position (nothing bent, smashed, pinched, folded, mangled, mutilated). Researching options now. May start a new thread - I think my options are:

1. Used PCM
2. New PCM
3. Aftermarket head unit only (retain stock amp and optical connection)
4. Aftermarket system (new head unit and amp)
5. Ipad Mini

Jako

With the PCM out, dies the fuse still blow? If not, the. You have likely narrowed it down to the PCM it itself. If it still does, the problem lies elsewhere.

iammulva

The fuse that keeps blowing is the 10a fuse that is on the back of the PCM. None of the fuses in the driver's footwell fuse box are blowing - all those are fine. So, based on that behavior (and having disconnected Dension), I'm concluding bad PCM.

wc11

Dead short on the power supply in the radio most likely if the fuse is popping instantly.

iammulva

Do you know if the power supply is available anywhere?