LMM: 09 LMM Weird No Start Issue

[duramaxnate]

Got a weird issue.

Truck is a 2009 Sierra, Truck had dead batteries when it came into the shop, so I charged them up fully, Good voltage to the truck, Go to crank it, Nothing but clicks to the starter, BUT when I put a diagnostic relay in (dummy relay with a switch) truck cranks.

Throwing the following DTCs:

P0633
(I will post any other ones in a few when I go check the truck again.)

Truck has the xx8594 Cal in (actually flashed a new one from GM).
The Vats light is NOT lit up on the cluster. Just the TPMS light and MIL light.
Key is already learned according to the tech 2.

Has anyone seen this? I always seem to get the troubled children..

I have been lacking in my visits lately, I promise to visit more often , Shop has been busy and growing.

[NC-smokinlmm]

Check grounds and reseat ecu connection.

[duramaxnate]

Originally Posted by NC-smokinlmm

Check grounds and reseat ecu connection.

Grounds were cleaned at the terminals and the had the ECM out to clean everything. Same results. Next thing I am doing is checking fuses for bad connections (could be something as stupid as that)

[gmduramax]

Originally Posted by duramaxnate

Got a weird issue.

Truck is a 2009 Sierra, Truck had dead batteries when it came into the shop, so I charged them up fully, Good voltage to the truck, Go to crank it, Nothing but clicks to the starter, BUT when I put a diagnostic relay in (dummy relay with a switch) truck cranks.

Throwing the following DTCs:

P0633
(I will post any other ones in a few when I go check the truck again.)

Truck has the xx8594 Cal in (actually flashed a new one from GM).
The Vats light is NOT lit up on the cluster. Just the TPMS light and MIL light.
Key is already learned according to the tech 2.

Has anyone seen this? I always seem to get the troubled children..

I have been lacking in my visits lately, I promise to visit more often , Shop has been busy and growing.

Just had something similar happen to my dads LMM. Was down for headgaskets went to start and batteries were dead. Charged batteries and wouldn't crank, gauges wouldn't work either. Disconnected the batteries and undid the bale connectors checked for bent pins. Hooked everything back up and it started fine and everything worked. No codes.

[duramaxnate]

Truck cranks with the key now!! Had a brain fart, forgot this truck had a battery under the passenger door on the frame, I thought it only had one. Well that battery was dead dead. Swapped both batteries out and everything is good. Going to finish it up tonight or tomorrow morning and she will start for the first time in a while. Btw, It's Black Mamba.