O7 Tahoe LT 4dr 4wd. 5.3 Flex. Check engine light on. Comes back with Codes UO100 UO101 comes back as miscommunication between ECM, TCM with possible causes open harness , corroded, or faulty ground code in either ECM or TCM. I can wiggle specifically what appears to be harness in the TCM. Photo below blue plug. I’ve been told to make sure I unhook battery, turn key into on and let be for 10 mins. So that way any capacitors, transistors etc holding any possible power are drained complete. Then to unhook clean harnesses from ECM, TCM check all connection points inside harnesses for corrosion, bent pin (highly unlikely but still mentioned) check wiring into harness etc for any possible bad spots aswell as all engine fuse panel grounds. Replug harnesses. Reconnect battery and pray. Is this correct way of doing this? Any correction or otherways to make sure ECM, TCM do not fry would be helpful! Thanks in advance!

Plug on back side no real play or wiggle room blue shown some.

 

disconnect battery, disconnect module.
if you want to discharge capacitors (I've never done it and never had a problem)...step on the brake pedal for 10 seconds after disconnecting the battery.

what modules are setting the codes and what module do they say is offline? ie code set in ecm for lost com with tcm
while the battery is disconnected but with the module still pluged in; you should be checking bus termination resistance. find the CAN bus wires in the dlc connector and check the resistance across the 2 pins(its a16 pin connector...find the 2 bus lines). you should have near 60ohms. if it read OL or 120ohms...the bus line is open

 

ecm for lost communication with tcm. Is exactly it. Seems to be an off in thing. Possible causes loose grounds corroded connection, open harness. They all make sense seeing how it’s an off on thing. The little bit of wiggle in that plug. I do have others that come back as same. Faulty ground on transfer case motor or faulty transfer case motor. aswell as front shaft speed sensor. All possible causes are open harness or faulty ground, bad connection. Ty!

 

Tech2. I Missed your point of wich module is sending codes. That I cannot be positive as Advanced read them jotted them down. Went in guy had time to quickly actual search causes. I have a code reader now doesn’t seem to be 1 appearing. When you say open can bus line do you mean as in wire somewhere maybe melted or corroded, chunk of dry cracked wire fell out. I think it was both. The TCM loosing communication with ECM and back and forth. Along with a faulty front prop shaft sensor, faulty rear abs sensor. Same as with faulty transfer case motor or ground. All possible causes seemed to come back as faulty ground open harness. Let me ask this. Seems as tho there is a main ground in diagram under main fuse box. Corroded under it appears. Would that be possibly it. I haven’t time to even pull battery cables yet or test. oHms out of can bus line. Before even unhooking battery Id like to get as many of the possibilities it may be. Then work one by one and do them all anyways. Doing it myself. Not to worried about labor obviously and rather just test all, clean all, possibilities and put back together and be done hopefully. Thanks man!