PCM 2 CDC 4 Problem

[Glenn 911]

We have a 2004 996 TT.  Our CDC 4 changer died.  We started getting TV,  CD changer, AMP, errors on the PCM 2 headunit. Of course the MOST loop

is not completed so we have no audio.  We purchased a replacment CDC 4 and assumed that when we installed the unit all would be restored.  The

new unit appears to be dead on arrival. I'm hoping that's not the case, but afraid it may be. My questions are :

 

There are three cables in the power connector  that attaches to the CDC 4, I believe I saw somewhere that ground is through the chassis which of the

three cables provides power, I'd like to connect the suspect DOA unit to an external power source to see if it's functional. (note : I verified the CDC 4 internal glass fuse

was intact)

 

Is there a fuse on the back of the PCM 2 that could have blown.

 

I do not have the Radio code for the PCM 2 if I remove the Radio is the only way to recover a PCM 2 code via the dealer ?

 

Would a MOST fibre loopback restore audio to the car ?

 

Any help would be appreciated !

 

Thanks

 

 

[JFP in PA]

We have a 2004 996 TT.  Our CDC 4 changer died.  We started getting TV,  CD changer, AMP, errors on the PCM 2 headunit. Of course the MOST loop

is not completed so we have no audio.  We purchased a replacment CDC 4 and assumed that when we installed the unit all would be restored.  The

new unit appears to be dead on arrival. I'm hoping that's not the case, but afraid it may be. My questions are :

 

There are three cables in the power connector  that attaches to the CDC 4, I believe I saw somewhere that ground is through the chassis which of the

three cables provides power, I'd like to connect the suspect DOA unit to an external power source to see if it's functional. (note : I verified the CDC 4 internal glass fuse

was intact)

 

Is there a fuse on the back of the PCM 2 that could have blown.

 

I do not have the Radio code for the PCM 2 if I remove the Radio is the only way to recover a PCM 2 code via the dealer ?

 

Would a MOST fibre loopback restore audio to the car ?

 

Any help would be appreciated !

 

Thanks

 

Welcome to RennTech :welcome:

 

Unless mistaken, I think you need to have the system recoded (PIWIS) when you change this unit out.

[Glenn 911]

 

We have a 2004 996 TT.  Our CDC 4 changer died.  We started getting TV,  CD changer, AMP, errors on the PCM 2 headunit. Of course the MOST loop

is not completed so we have no audio.  We purchased a replacment CDC 4 and assumed that when we installed the unit all would be restored.  The

new unit appears to be dead on arrival. I'm hoping that's not the case, but afraid it may be. My questions are :

 

There are three cables in the power connector  that attaches to the CDC 4, I believe I saw somewhere that ground is through the chassis which of the

three cables provides power, I'd like to connect the suspect DOA unit to an external power source to see if it's functional. (note : I verified the CDC 4 internal glass fuse

was intact)

 

Is there a fuse on the back of the PCM 2 that could have blown.

 

I do not have the Radio code for the PCM 2 if I remove the Radio is the only way to recover a PCM 2 code via the dealer ?

 

Would a MOST fibre loopback restore audio to the car ?

 

Any help would be appreciated !

 

Thanks

 

Welcome to RennTech :welcome:

 

Unless mistaken, I think you need to have the system recoded (PIWIS) when you change this unit out.

 

Thanks for the Welcome and the response, are you saying I may need a recode to have the new CDC4 unit accepted or

that if I eliminate the CDC4 and do a loopback that I may need a recode ?

[JFP in PA]

 

 

We have a 2004 996 TT.  Our CDC 4 changer died.  We started getting TV,  CD changer, AMP, errors on the PCM 2 headunit. Of course the MOST loop

is not completed so we have no audio.  We purchased a replacment CDC 4 and assumed that when we installed the unit all would be restored.  The

new unit appears to be dead on arrival. I'm hoping that's not the case, but afraid it may be. My questions are :

 

There are three cables in the power connector  that attaches to the CDC 4, I believe I saw somewhere that ground is through the chassis which of the

three cables provides power, I'd like to connect the suspect DOA unit to an external power source to see if it's functional. (note : I verified the CDC 4 internal glass fuse

was intact)

 

Is there a fuse on the back of the PCM 2 that could have blown.

 

I do not have the Radio code for the PCM 2 if I remove the Radio is the only way to recover a PCM 2 code via the dealer ?

 

Would a MOST fibre loopback restore audio to the car ?

 

Any help would be appreciated !

 

Thanks

 

Welcome to RennTech :welcome:

 

Unless mistaken, I think you need to have the system recoded (PIWIS) when you change this unit out.

 

Thanks for the Welcome and the response, are you saying I may need a recode to have the new CDC4 unit accepted or

that if I eliminate the CDC4 and do a loopback that I may need a recode ?

 

 

It is my understanding of the PCM of your vintage that when components are replaced, like the CDC 4, the system has to be recoded to accept it.

[Loren]

As JFP in PA said there are requirements for different options in a MOST system car.

For your model year you need the correct cables and cable end points for your car's exact configuration.

Once those are correct the system must be re-initialized to find all the correct components - this can only be done with a Porsche specific diagnostic tool (PIWIS or PIWIS 2). 

 

(Click images to enlarge)

 

[Glenn 911]

Thanks for the responses guys I really appreciate the information !

 

I'm still concerned that the replacement unit was DOA as I don't believe the PCM would cut power

to this device and I am unable to feel/see/hear any indication of life when I hit the eject button.

 

I'll have to verify that with an external power system test before I make the trip to the dealer.

 

Thanks Again !

[wross996TT]

 

Is there a fuse on the back of the PCM 2 that could have blown.

 

I do not have the Radio code for the PCM 2 if I remove the Radio is the only way to recover a PCM 2 code via the dealer ?

 

Would a MOST fibre loopback restore audio to the car ?

 

 

There is a fuse on the amp.  The radio code is stored in the ECU for your year.  Loren & JFP covered the other.

[Glenn 911]

Problem Solved !

 

What I learned along the way :

 

With the cd changer out of the loop the MOST bus was interrupted.  I was getting a tv, cd changer amp fault.  I built a Digital audio loopback connector and was able

able to restore audio.  Still getting the TV and cd changer fault.  I was testing the input leads and could not detect power coming to the cd changer.  I found a blown

fuse in the E row 6 or 7 I believe a 7.5 amp fuse.  I replaced the fuse and connected the new changer power and MOST bus, started the car and everything worked. 

I didn't have to get a recode on the swapped out cd changer it worked fine. 

I still get the TV fault, I have no idea what that is indicating based on what I've learned and from everyone's input possibly a backup camera was coded into the system.

I'm having issues with the NAV not finding satellites and Clocks not setting , which I've had since we bought the car but those issues are for another day.

 

It's amazing how much fixing the radio cleared up the "static" generated when the passenger seat is occupied ....... ;)

 

Thanks to JFP in PA, Loren and wross996TT for your assistance !