Fault Codes stored on Key fobs
I have been chasing this issue for a while now. It started with transmission failure safty program light, and a 4x4 light when I started the truck on cold mornings (45 degrees or less) So I replaced the battery with a new 720 CCA battery from BMW dealer. Truck worked fine for about a year on the the second year with the new battery same proble came up. So I bought a Bently Service Manual and start chasing this issue. I checked the alternator with a voltmeter at the battery terminals with the engine running at idol and got an accpetable reading according to the manual. Also the alternator was charging fine at least in the warming weather. By the way this never happens in the Spring Summer and early to mid fall. After checking the alternator and checking the battery which were both good, I decided to get a mega-tron 900CCA (cold cranking amps) 1000 AMPs 1000 cranking amps battery. Did so the problem, with during cold starts but not only do I get the transmission failure safty program light, and a 4x4 light but also the ABS and Brake light come on. So I diconnected the negative battery post overnight in hope to reset the ECM. Still no luck same issue happened during a short test drive (1/2 mile run) Then as I am going to work i just so happen to use the orginal key that came with the vechile and no lights, NOTHING! at all works fine.
So I plan to use the old key for a week or two and see what happens. But my questions is could it be that the New Key Fob has stored fault codes and can't release them and or could it be that the Old Key Fob can't remember fault codes? I reflect back to times taking my 335i into the dealership for warranty service and they could read information just from the key and I think the 2004 X5 E53 has this capability as well.
Anybody have any comments or suggestion about this issue?