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2003 996 CDR-23

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CDR-23 (or later):

These radios do not have a security code - that is, not that the user enters.

These radios are security tested on the MOST (fiber optic bus) system to see if they are the "programmed" radio. The radios are programmed and recognized by the car’s DME and can only be replaced by a shop with a PST2 or PIWIS. These radios will not request a code when battery power is disconnected.

Not sure if this is the right place for this question, but I'll give it a try.

I have a 2003 996 with a CDR-23. It is the base stereo system, no amp, no upgrades.

The fiber port on the CDR-23 has nothing connected to it, just a dummy plug in the hole, so obviously in this case the radio isn't communicating with anything over the optical bus, and works fine after power is disconnected.

  • Does this mean that this particular CDR-23 has no security programming requrement?
  • Will all CDR-23's work without a car specific programming as long as it is in stand-alone mode not communicating with anything else on the MOST bus?
  • If this radio was used to replace a CDR-23 on another vehicle that did have a bose amp / MOST bus, would this head unit, which works fine in stand-alone mode,then need dealer reprogramming to work once connected to another vehicles MOST bus?

Thanks in advance for any info on this.

Edited by pfbz
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  • Admin

The code for the CDR-23 is programmed into the control box using a Porsche (only) tool.

If the radio comes on then you have nothing to worry about.

If you try and swap a CDR-23 from one car to another it will not work. Each radio must be programmed for each car (just like your remote key).

It does not matter what options were on the car it came from if it has been programmed to your car. Again, if the radio comes on then you have nothing to worry about.

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Thanks for moving my post to the correct place.

I understand your description of how the CDR-23 programming works, and it makes perfect sense for units that are connected to the MOST bus, as I assume most CDR-23's are.

But if the head unit is not connected to the MOST bus (my factory config), I don't get how it could either be programmed by a dealer or detect the s/n of the vehicle it is installed in...

Edited by pfbz
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The security code stored in the CDR23 is matched with a code programmed in the DME. If the two codes match, the radio comes on.

The codes are not transmitted by the MOST bus. They are transmitted by the diagnosis line. This is a white/red wire connected to the green plug on the CDR.

Edit: There are companies who can remove the security codes, so that it can be used in any car. I know of 2 or 3 in the UK, but none in the US, I'm afraid.

Edited by Richard Hamilton
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The codes are not transmitted by the MOST bus. They are transmitted by the diagnosis line. This is a white/red wire connected to the green plug on the CDR.

Thanks... That makes sense. And presumably if the diagnosis line is not connected, it goes into lock mode.

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  • 1 year later...

I have a 2003 996 cab. The cdr23 suddenly stopped producing sound even though it visually appears to be working fine. I have read that this problem can be a bad head unit or a bad amp. Is there a way to determine which of these two is the problem? I do not have BOSE or CD changer but do have an amp and believe I have MOST. Any help with this problem would be deeply appreciated.

Thank you,

Roy Parnell


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