Yesterday I experienced low voltage that was not enough to engage to start.
I had to disconnect the 12 volt battery and reconnect after 30 second, and then It showed 15 volts. Today it's back to 13 volts.

Does any one know how the hybrid modular work. knowing that I have already addressed the transmission wiring harness recall, updated the hybrid modular. but not the later clutch adjustment recall.

 

So, to clarify, your Yukon would not start, then you disconnected and reconnected the battery, then it started?
Was there a message that the battery was too weak? What made you decide to disconnect the battery?
Very interesting fix. I wonder if you are missing one of the software upgrades they did for the battery issue.

 

some needed a 12v battery REPLACEMENT (mostly early cars)

 

Could it possible be a bad ground?

 

Good idea Ken: Check the engine to body ground straps for good connection.

 

The engine body ground straps is checked. Could this be related to the transmission wiring harness recall? Mine was mnfg in Dec/07 and I had the old one repaired and I'm still waiting for a new one to arrive on the 8th. dose any of you know if the replacement have a different electric rout or its just about the bad connection.

 

I would say that if the tech does not follow the exact instructions of the TSB, then yes, he could have routed the cable differently. But I don't see how that could cause an issue unless it is subjected to heat or electromagnetic interferrance in the new location. More than likely, the cable would not reach if it were routed incorrectly. Just my thoughts but I am just guessing on this one.

 

In the early 2008 production run there were more than a "normal" amount of problems with the 12V batteries not holding charge. Frankly a battery supplier problem. There should be a bulletin out to replace the 12V battery with a newer and/or even larger capacity one if yours fails the load test... a standard 12V battey test.

The Dec/07 is in that early batch.

The transmission (internal) harness has nothing to do with 12V power distribution to anything other than the transmission controller inside, but it does carry important (position sensor) signals from the motors to the hybrid controller.

The position circuits are very sensitive. They send the position of the motor rotor to the hybrid controller for maximum efficiency. By knowing the rotor angle relative to the stator, the electric slip angle can be controlled exactly.

 

now that make since. so if the wiring harness is less than perfect, it could send the wrong message to the hybrid modular and cause it to shut down the system to protect the motor rotor from any damages.

I'm getting the harness shipped to me from the US on the 8th. I will have it installed by the dealer.

I'm going to have the mechanics test the old one and report back to the thread.

 

The 12V battery passed the load test. (12.7 Volt). did I mention I get 12V when the ignition is on, and when I start it moves from 12 to 13 then 14 and it get to 15 before it get down back to 13V. every one I talked to gets 14v at all times!