I've been trying to get in to this ECM and TCM for awhile now. Its a 2008 5.3L and 4L60E (E38 and T42) in a custom built Jeep. I've tried all the tricks I know, I have ohmed the class two wires, there 120 ohms resistance between the two of them, ALDL port has power, and good grounds, I've tried swapping TCM's with no luck. I can't scan the Jeep with it running, and it tells me the same thing, unable to connect to to VCM. We have tried other computers with hp tuners installed on them and the only one that seems to work is the one that origanaly flash the ECM for deleting emission codes and programming fans and tire size and gear ratio. He want to start tuning on it but we don't have access to that other computer anymore and we want to tune it.
Any Ideas would greatly be helpful.
Thanks,
Holden