2002 M3 Key Issues

I recently bought a 2002 M3, and got 2 remote keys with the car. they both lock and unlock the doors ect, but only 1 will start the car continuously. if i start the car with the "good" key, and turn it off, and put the "bad" key in, it starts, but if i turn it off, and try to restart it with the "bad" key, it wont work. whats going on???

Have you tried driving around for a while while using the "bad" key?

i drove around for about 30 min but that didnt help. maybe i should drive longer??

The keys contain a battery, I was thinking maybe it wasn't charged. I suppose the battery could have gone bad. This doesn't explain the sometimes starting though.

does the key pass an electronic code to the security system(ECU)?

it could be alot like a CMOS battery of a pc....where it has to have 5 volts to keep stored settings in memory when the PC is turned off...

Originally Posted by dawgbone

does the key pass an electronic code to the security system(ECU)?

it could be alot like a CMOS battery of a pc....where it has to have 5 volts to keep stored settings in memory when the PC is turned off...

AFAIK, that is correct.