Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
U codes are communication codes which is exactly what you are experiencing with lost of GMLan. This is the communication link between all CPUs including the TCM, so yes hard shifting is also a symptom. Had this problem with the 07 almost 2 years ago and it hasn't come back. I can't tell you which of the 2 was my problem since I did all of it at once.
U2105 Lost Communications with Engine Control System- BCM, EBCM, PSCM, TCM
U2107 Lost Communications with Body Control System- EBCM, ECM, IPC, PCM, PSCM
Never drive faster than your guardian angel can fly
Last edited by Coby7; 09-11-2015 at 06:17 PM.