My 2008 997.1 occasionally has a right rear brake light failure alert in the instrument cluster as well as being physically out. The failure typically self corrects either when the brake is depressed or after 5-10 minutes. I think the problem started a few months after I swapped out the factory radio with a newer Alpine Head unit. Is this a build up of failure codes or is something else causing this and how can it be fixed? Thanks.

 

.1s have old school bulbs. Dirt, corrosion and wear can affect the contacts. First thing to do before getting to complicated is take them all out and give everything a through cleaning. Better, grab some new ones beforehand and replace any that look funky.

 

I've also seen where when you plug the taillight into the connector harness instead of all the pins going into their slots, one is a little off and it will actually push the wire loose from the taillight connector that's supposed to hold it in position. This will cause an intermittent connection instead of the pin fully seating into the receptacle. Take that connector apart and look down in the end to see if all the pins are at the same height. If not, grab some thin nose needle nose pliers and pull the pin back up until you feel it seat into the connector properly. Then where all the wires exit the plug, wrap a wire tie around them as a bundle and pull it as tight as you can get it - this prevents that one wore from being able to get moved on its own. Then when putting the connector back together, do it slowly paying attention to feel for any resistance as the pins start going in. Once it feels like they all all slid in properly then squeeze the connector together until it clicks.

 

I had this happen once and it turned out that the filament inside the bulb was broken but in such a way that most of the time it made contact.

 

x2- 1/2 broken filament. Worked most of the time, and threw the odd code. Took the bulb out, it looked fine. But if you shook it, the filament would come loose. Then reattached itself.
I had a bulb out on my X5 in the fall. Replaced the bulb. Then the other side went out. Then the turn signals, then a reverse bulb. I just changed everything. They have served their service life.
I'm sure doing all the rear bulbs is 10-15 bucks. Good isolation job.

 

X3. Also happened with an old-style headlight I had on my 1975 Toyota Corolla. I got pulled over in TX for having a headlight out. I asked the highway patrolman to show me, so he let me get out of my car and walk to the front. While he was looking away, I hit it with my fist, and it came back on! I showed the officer it was working, and he gave me "that look." I told him I would stop in the next town and buy two new headlights (they were pretty much universal then, remember?) and change them both, which I did. I didn't get even a warning.