Has anyone ran into this problem?
Problem, Vehicle shows no codes but TCM will not command anything but 2nd Gear.
History, Customer has a 2009 GMC 1500 2WD with a Upgraded 6.2L. Customer shelled the 240k mile trans and decided to have a shop install a 4L80E. They got it installed and asked me to come by and help after a no crank no start symptom. Reviewed the schematics I found the original 4L60E transmission had an internal mode selector switch and the 4L80e of course has an external switch. I reviewed the 2009 GMC schematic and pulled the necessary pins from the Transmission Connecter and spliced them into an external harness wired IAW a 4L80E transmission and plugged that into a new external mode selector switch, the truck now starts and goes into gear. Also the instrument cluster position indicators work properly and all status data in HPtuners reflect properly. Used HPtuners to perform a segment swap from a 2009 Chevy Express Van which has a 4L80E and same TCM to the current TCM. Tested transmission and only gets 2nd gear, no codes. Continued reviewing the schematics and conversion adapter and identified the 4L60E for this 2009 year does not have an internal MPS, Manifold Pressure Switch assembly and wiring going to the TCM. I reviewd the 2009 Chevy Express 4L80E wiring schematic and it does utilize this switch and inputs. These are the only differences in the wiring between the two model vehicles I have identified.
My next TS step was to contact the MFG of the harness the customer bought, possibly they know of any known issues and could advise, the 4L60E to 4L80E adapter harness used is from ICT Billet. P/N WATRA31-18
I contacted ICT for tech support and they advised every time they had this problem it was caused by a improper segment swap. I brought up the missing MPS circuits and they said that most likely isnt the problem. I performed the segment swap again and still the same result, it will only command 2nd gear. Since I was getting the same result with HPtuners I decided to flash the TCM with my Snap-On PassThrough Pro with the Chevy Express 4L80e flash file and unfortunatly I get the same results. As far as I can tell, those three missing MPS circuits are the only difference between my current 4L80E installation and a factory Chevy Express Van.
If anyone knows if the MPS circuits are necessary or has any additonal information to add I would appreciate any feedback. Regardless, I have already ordered new pins to repin the TCM connector and run the missing circuits to the 4L80E. If this does fix the problem then I will provide an update just in case someone runs into this problem.
Thanks in advance.