Hey guys, i just done a Calflash with the 12212156 OS and a crank relearn... Now i have a flashing battery light.. WTF?
Code P1638 "Generator F-Terminal Circuit"

Whats all this about???
I need help fast because i have to drive tom...

 

no big deal man, just disable the code! it wont hurt anything.

 

OK i was fixin to get mad agina... haha thanks bro.. fixin to disable it right now... and then start on the tuning...
got to install a 2 bar map and fix up a COS...

 

The reason it's on....99-00 trucks are 2 wire alternators. They have the main charge wire and the L-terminal to "turn on" the alternator and tell it to start charging. In 01 they also started using the F-terminal, which is a field sense wire that provides some sort of feedback from the alternator to the PCM. Since you upgraded to a newer OS, your PCM is now looking for the F-terminal signal. As DLH said above, you can just disable that code and you'll be fine.