I walked up to my 2007 A3 this weekend and the remote wouldn't unlock the doors -- that's never happened before. I assumed the battery in the key fob was dead, so I used the physical key to open the door then start the car. The car ran for a few seconds and died.

Audi Roadside Assistance told me it sounded like the car lost the signal from the key so when I used the physical key, it thought it was being stolen and disabled itself. They said the car would have to be towed to the dealer and reprogrammed with all of the keys.

The dealer called me the next day and told me the radar detector I connected to the fuse box was the source of the problem. Initially he said he "thought that might be the problem" but by the end of the call he said he was "100% sure that was the problem." He didn't understand exactly what he was talking about, but said that the car saw an unauthorized electronic device connected to the harness and that was the cause of the car going into "Default" (or anti-theft) mode. He didn't sound confident: at one point he told me it was the connection to the fuse box that caused the problem and later told me radar detectors can interfere with the [immobilizer] signal.

Is that possible? The car has been running fine for months with that radar detector installed. I've never had a problem with remote entry or starting.

I'm not sure this information is relevant but: (i) I keep the valet key in the glove compartment and (ii) the key that failed was purchased aftermarket and I had the same Audi dealer program it.

Sorry about the long post. Any thoughts would be appreciated.

 

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