I will start with this is a 2008 GMC Yukon Hybrid. I have within the last year replaced the motor with an $8,000 price tag. My hybrid is now while in Drive staying in auto-stop. Mainly when I start off from a stop light or stop sign, it goes into auto stop and doesn’t come out. If it does it will abruptly jerk or lurch forward or even backwards. When it is in park, it continually jumps in and out of auto-stop. My gas mileage has gone to a steady 19-20mpg to currently 12mpg which my be due to my wife using remote start due to the Texas heat but I do not believe that is the only reason. I have looked at multiple threads and I have replaced the auxiliary transmission fluid pump, added transmission fluid, checked wiring connections, took out and put back in almost every fuse, and unhooked the battery with no resolve. I took it to the shop, they stated it had to go to the dealership due to the bulletins and codes. The dealer ship read the codes p079ac1 slip, po797pcs3 on, p9715pcs4 off, p0796pcs3 off, p0756ss2 off. The dealership gave me only two options, replace the transmission for $6000, or tear it apart for $1000 and that’s without fixing anything. He stated the codes were internal transmission codes. However we can drive the vehicle in M mode with absolutely no problems. It drives just fine in manual mode. It seems to have a higher pitch whining noise and I’ve noticed the drivers rear tire area has a creeping Boise after I turn the car off that I didn’t notice before. A few door locks have stoped working and the clock on the touch screen seems to get stuck on a time and then all of a sudden will jump to the right time. I haven’t tried the control module because I don’t want to just throw $1000 at it here and there guessing. The battery voltage stays about 13 or 14 volts. The hybrid display still states that it is using hybrid power. I have another appointment at a different dealership for a second opinion. I have also considered the drive clutch motor, and suggestions would be greatly appreciated. I really would like to get out of spending another $6000 on this thing.

 

I have also tried starting suv with the hood open. The suv stays out of autostop whole the suv has the good open but once closed, it continues to go in and out of autostop. Also continues to get stuck in auto stop while driving. If it gets stuck in auto stop and I switch to manual mode, it will with a little delay jump back to the ICE.

 

I've dealt with this issue, it's most likely one of two things: the automatic transmission fluid pump ATFP or the automatic transmission fluid pump control module. On the one I was working on it was the module. I ordered both the pump and the module just in case (cannot get new ones at this point). The parts came from an 09 Tahoe, I put it in a Yukon, but it required swapping the harness connectors because even though they had the same color and number of wires, the connector was different. Put that in and problem was solved!

 

These GM two modes are complicated and have unique systems that most dealers and independent shops have a hard time diagnosing the issues.
Do you have any vehicle history that you can share with the forum. we all love to make guesses.
Did you buy this new? What DTC codes are set? Why the engine swap and who did the work and what was the engine source? What other work has been done on this unit over the years? How many miles currently on this unit? Other info that you might have or that you can think of (even if it may not seem to be related to the current issue) that might help..........
This could be a lot of fun. Once everyone is quarantined inside their homes for the Covid-19 we will be needing some vehicles to diagnose on over the internet to keep us from getting bored. Hopefully the virus cannot be spread over the internet!