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Used Porsche Cars for sale in Slough, Berkshire | RSJ Sports Cars

PCM not working after shock.

G

goldblum

New member
Joined
10 Dec 2017
Messages
6
Hi all! :)

Please can I get some advice.

The battery went dead in my 911 carrera s - and I read on the internet to get the bonnet open - connect a car battery up to the door And it releases the catch "” this worked great!

BUT...

It stopped my PCM 2.1 from working. No life at all. The multi cd changer still moves - nothing on pcm screen, or no sound.

I've checked the fuse at the back of the pcm - and it's fine.

Porsche themselves have quoted £2.5k for a referb replacement - but at my last mot the mechanic said it might need a 'code" putting in by the dealer to make it work again - but Porsche never mentioned this as an option on the phone.

Can anyone offer any help/advice?

Thank you! :)
 
Hi goldblum sorry I can't help with the coding but 2.5k for a unit :eek:

If you go down the replacement route I would try to find a second hand one from eBay or Porsche parts dealer the money OPC are asking is crazy. If you want to keep the same unit there are places that will repair it

https://m.ebay.co.uk/itm/Porsche-Pcm-2-1-/142613424357

https://m.ebay.co.uk/itm/Porsche-PCM2-1-navigatino-radio-CD-Headunit-repair-service-/182903009117

Let's also see your car we all love a photo of new members cars :thumb:
 
There is also a fuse in the fuse board in the drivers footwell have you checked this.
 
Thanks guys :)

Yes - I should have mentioned - I've checked fuses in footwell - all fine :(

I cannot see anything physically wrong anywhere. That's why I was hoping it might be a software fix.

Does anyone know if a pcm will power up if I plug it into another cars audio connector?

Even if it's just an error message - just so I can see there's still some life in the pcm :)
 
Surely this is a great excuse to throw your PCM 2.1 in the bin and get something decent instead? I might need to take notes on this PCM sabotage to expedite my upgrade!
 
You will need to check the plug at the PCM for 12 volts permanent , 12 volts ignition on and an earth .. if it has those but wont turn on then i expect the unit has died im afraid .


Yes you can plug it into another car to test but quicker just to check the feeds/earths on your car.

Normally it blows the fuse in the PCM but i have seen dead PCM,s after jump starting before.

There are companys out there that can refurb your PCM if it is dead so maybe research that first .


EDIT

Technically you could code off the PCM in the gateway controller but i have a feeling it will still power up so i dont feel that its going to be a coding issue but theres no way of proveing with out connecting a tester .

My guess is if you do you will just be unable to talk to the pcm which would indicate its dead .
 
Thanks again for the replies! :D

I think I'll try and buy a second-hand unit from eBay. To be honest - I never even thought about that. D'oh.

Does anyone know if they are locked to the specific car? Or will it just be plug-and-play straight swap?

@tom_nieto I did look into a new system - but to get it to work with the optical cable and the bose system was just beyond me.
 
Demort said:
Normally it blows the fuse in the PCM but i have seen dead PCM,s after jump starting before.
Click to expand...

Out of interest Demort - do you have any idea why doesn't the fuse blow?
 
Im afraid im no electronics expert but i belive there are several members here that are .

Ive spiked my amp meter before which has a 10 amp fuse in it .. i hit 15 amps and it didnt blow on a spike / surge .. not a permanent feed .. another time i briefly saw 26 amps on said meter before the fuse blew .. thats a Cayenne alarm tripping btw .

So a fuse can allow a higher voltage through but is designed to fail as soon as possible to try and protect components or wireing.

My best guess is a high amp spike has damaged the PCM but was such a short burst that the fuse didnt have time to heat up and melt .


Any component that has a permanent feed going to it is susceptible to a surge on a jump start but the PCM is the main one that can suffer.

A reverse polarity of the battery will also kill it along with several other control units .. basically thats bad !


Edit..

Personnely in your shoes then i would see about getting your one repaired .. also we have not yet proved you have x2 feeds and an earth needed to make it work :)
 

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goldblum said:
Thanks again for the replies! :D
Does anyone know if they are locked to the specific car? Or will it just be plug-and-play straight swap?
Click to expand...

The PCM2.1 is not locked or coded to a specific car - if you buy an ebay like for like replacement it will fully work no problem in your car.

It is only from the PCM3.0 onwards that Porsche started coding and locking the PCM's specifically to each individual car via the Vin No.
 
Demort said:
You will need to check the plug at the PCM for 12 volts permanent , 12 volts ignition on and an earth .. if it has those but wont turn on then i expect the unit has died im afraid .
Click to expand...

It's the first chance I've had to check this - I've got a permant live - but no ignition 12v "” is there a hidden fuse somewhere? Or any way to fix this?

Thanks again for the help everyone!
 
My pcm connector doesn't seem to match up to the image I could find online. Could anyone advice which lead should be the 12v ignition

Thanks for the help! :)
 

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There isn't a 12v switched ignition in the hu wiring loom!
I don't really understand it but it's all to do with canbus and clever electronics.
There is just a permanent power feed.
I know this because I installed an aftermarket hu and had to run a 12v switched feed from the fusebox.
 
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