head unit continually cycles

[ericinboca]

2003 C4S

CDR-23 head unit with multi CD changer in front trunk

No PCM stuff installed

The head unit cycles on and off, over and over again, showing only PORSCHE on the display and then going away, coming back, etc.

I pulled the head unit out and checked the connections to be sure they were seated correctly - they were. I also checked the radio fuse in the panel and the 10 amp fuse in the back of the head unit. And I checked the connections to the multi CD player thing.

Durametric gave me an error code that pointed the blame at the receiver, saying it is faulty. I don't remember the fault number with certainty, but think it was 54...would check it, but I am in Calif at moment and car is in Fla.

I have an identical CDR 23 head unit out of my 04 986S (turned into a race car).

Couple questions -

• How do I know it is the head unit and not the amp? In this car, is the amp part of the CD changer? (My 986S had an amp, but no multi CD unit.)
  
• If I replace the head unit, will I need a PST2 or PIWIS to tell the immobilizer the new head unit is OK? If I install the new head unit in my garage without a PIWIS or PST2, will the car start?
  

[judgejon]

2003 C4S

CDR-23 head unit with multi CD changer in front trunk

No PCM stuff installed

The head unit cycles on and off, over and over again, showing only PORSCHE on the display and then going away, coming back, etc.

I pulled the head unit out and checked the connections to be sure they were seated correctly - they were. I also checked the radio fuse in the panel and the 10 amp fuse in the back of the head unit. And I checked the connections to the multi CD player thing.

Durametric gave me an error code that pointed the blame at the receiver, saying it is faulty. I don't remember the fault number with certainty, but think it was 54...would check it, but I am in Calif at moment and car is in Fla.

I have an identical CDR 23 head unit out of my 04 986S (turned into a race car).

Couple questions -

• How do I know it is the head unit and not the amp? In this car, is the amp part of the CD changer? (My 986S had an amp, but no multi CD unit.)
  
• If I replace the head unit, will I need a PST2 or PIWIS to tell the immobilizer the new head unit is OK? If I install the new head unit in my garage without a PIWIS or PST2, will the car start?
  

Loren has commented on this issue in the past. I think it should be classified as a pinned topic, under "mysterious Porsche issues." This happens occsionally to me. It's solved by either putting in cd, then removing the cd once it begins to play, (this works if your driving along), or stopping the engine, removing the key, and starting up all over again. I'm not sure there is any real answer, and I'd wonder if you really need to replace the head unit. good luck

Edited January 22, 2010 by judgejon

[juniinc]

replace the head unit

[Loren]

I have no problem (and any moderator can also pin) - but I would prefer a "known" solution before pinning.

I think you kind of need to have PST2 or PIWIS actively running on the car at the exact time this occurs. Then look at the fault and potential causes.

[ohhh my]

i'm currently having this exact same problem on an 03 Boxster S with Bose. I haven't tried inserting a cd to see if it fixes it yet, but it's been 2 days and the only thing my screen displays is PORSCHE.

[ericinboca]

i'm currently having this exact same problem on an 03 Boxster S with Bose. I haven't tried inserting a cd to see if it fixes it yet, but it's been 2 days and the only thing my screen displays is PORSCHE.

My problem ended up being a bad fiber optic cable from the CD changer. Replaced that cable and have had no trouble since.

First I sent the head unit off for a bench test and it pased. The shop that tested the head unit felt pretty strongly it was going to be the cable, and he was right.

Edited August 16, 2011 by ericinboca

[ohhh my]

Thanks for the follow up post. I did go out to the car earlier and tried sticking in a CD and it did not fix the problem.

Is it the fiber optic cable from the CD changer to the amp? or CD changer to the headunit? and is this something I can replace myself?

Thanks in advanced for any information you can provide. cost would also be greatly appreciated.

Take care,

[ericinboca]

Thanks for the follow up post. I did go out to the car earlier and tried sticking in a CD and it did not fix the problem.

Is it the fiber optic cable from the CD changer to the amp? or CD changer to the headunit? and is this something I can replace myself?

Thanks in advanced for any information you can provide. cost would also be greatly appreciated.

Take care,

In my 03 996C4S, the CD changer was a dealer installed option, using Porsche stuff. The CD changer is in the front trunk, as is the amplifier. If I remember correctly, there was a cable that ran from the amp and a cable that ran from the CD changer and they both merged to make a Y shaped cable which then connected to a single cable running to the head unit. The connection to the cable that ran to the head unit was under the carpet somewhere around the brake fluid reservoir. I replaced the Y shaped cable. It was easy. I might even still have the bad cable with the part number. I'll take a look this afternoon.

[ericinboca]

Faulty memory - the cable does not have the part number on it. I've attached some images, though, that might help you locate the cables.

First image is of the Y cable I replaced. This solved the problem for me, although I suppose if this didn't work, I would have next suspected the CD changer and sent it for a bench test.

Second picture is of the front trunk of an 04 986S which has been stripped of all the carpet etc. (it is a race car) You can see circled the end of the fiber optic cable where it used to connect to the amplifier, and the arrow shows where that cable connects and goes into a protective plastic conduit before heading off into the cockpit. It is at this place where the CD changer and the amplifier came together in my 996.

Third picture is of the front trunk of my 996. The circle is the general area where I found the connection for the Y cable, and the arrow just happens to be showing where the amplifier cable is showing a little bit.

Hope the problem ends up being a cable for you too - while not cheap, it is less expensive than the head unit or the CD changer.

[ohhh my]

Thank you so much, very helpful! This setup is similar to mine! I'm going to call the local dealer to purchase the cable and will replace. Thanks again!!!

[ericinboca]

You might want to ask about returns and restocking fee up front in case the cable it doesn't do the trick. Like I say, it worked for me, but I imagine it could be the CD changer, the cable, the cable to the head unit or the head unit itself. Good luck!

[ohhh my]

Will do. I have the part number 996-622-705-00 and it's about $292!!!

[coleta]

Eric, did you replace the cable just based on the feedback from the shop or did you see something physically wrong with it?

What shop did you use?

Thanks

[ericinboca]

Eric, did you replace the cable just based on the feedback from the shop or did you see something physically wrong with it?

What shop did you use?

Thanks

I first checked the cables using a light - did it transmit the light. The cables transmitted light. I checked all the connections, power supply, etc.

I pulled the head unit and sent it to beckerautosound.com

They did a bench test and called me back to give me the results. I talked to the tech about the problem and he said he really believed it was the cable. So I tried, and it worked. I figured if the cable transmitted light, it worked, but maybe not. Bench test was $70. I forgot the cost of the cable (listed above) but I do remember my reaction - "holy sh*t"

In retrospect, I should have sent the CD changer off for bench test too, just to absolutely ensure it was a cable. But I got lucky.