Porsche Enthusiasts Club Forum

I went to de-hibernate my wife's 2004 996 Carrera 4S yesterday and found that the trickle charger had failed - battery dead. When I tried to start it there was a disco light show on the dash.

I replaced it with a new battery and it started first go. However since then there is no power to the radio/sat nav and worse, the Tiptronic is in limp mode.

Does anyone have any similar experience, or any suggestions as to what to do next?

With the battery charged, disconnect both leads to it & short the leads out, not the battery, use a spanner or similar. Then reconnect the battery as cleanly as you can. In other words get the battery lead on first hit.
That may clear it although it'll run like a bag of spanners until the DME relearns the engine parameters, may take quite a few minutes. The tip box will act strange for the same reason.
If this doesn't cure it then it'll need scanning. Sometimes if the battery goes flat it forgets which options it has & they need adding in. Needs someone with a PWIS or similar.

Update on this. Codes cleared with PIWIS and the Tiptronic is fine. I have a good amp to fit which might cure the PCM issue....

What a pain, I would be tempted to take the car to your nearest OPC and ask them to plug it in. Or take it to a local gear box specialist and see if they can reset the box. It’s a Mercedes box so fairly common.

The PCM has 3 fuses one of them is internal.