Hi, we are working on a LMM Duramax/Allison conversion over here in Australia (GMC powertrain into a Nissan Patrol - a common mod) and have just one bothersome code we cant resolve. As you would expect we dont have any tapshift with this code active.
Any assistance or tips would be very welcome, as this is not a common code to us at all.
We have thoroughly checked all the harness connections and general integrity, all pins in good condition each and every one inspected (harness is custom made from GM donor by an experienced conversion shop - done approx 40 with no issues).
Checked CAN circuit, 60 ohms and good continuity, twisted pair still intact.
Verified continuity from Trans to TCM and ECM.
Verified all pin connections to BCM (we only use a small portion of this).
Swapped TCM, BCM, ECM and GPCM from a working LMM conversion (one at a time, no change to active code)
Removed Trans control valve and fitted new harness and NSBU, no change.

We did read one random piece of info that indicated this code may be induced by unmatched operating systems in TCM and ECM?
any thoughts on that one please is it possible?
(if so our swapping of ECM/TCM still may have resulted in a mismatch).
We appreciate any thoughts or areas to check!