Don Brew,
I didn't have the TCM unplugged, just remove from tray and folded back out of the way. Unless there is a connection through the top plug on the ECM which was unplugged.

 

I suggest you try checking the TCM connector and look for damage to the pins. Disconnect the battery negative terminal for 15 minutes and check the connection, tighten the four bolts in the fuse box real tight. Then reconnect the battery.

 

Got quick few minutes to look further into the TCM problem, I pulled the only connector I had unplugged off and cleaned with CRC cleaner, didn't have any grease but also chaecked for missing or bent pins and put back together with no change. I then jumped a ground wire to the TCM case and the problem went away. I didn't have any more time but I guess I need to chase the grounding for the TCM as something may have broken folding the wires harness back. Until next time, got doctors visits and gas well problems to deal with.

 

I did not say anything about the TCM. You said the top plug on the ECM was unplugged. a pin or so is probably either bent or pushed out the back of the connector.

The TCM goes to ground via the blk/whr wire on terminal 49 of the plug. That is the pin all by itself. It is on the same circuit as the ECM ground. That is the pin all by itself also. Then to the ground point on top of the trans.

I hope you can extrapolate why the ECM plug might have something to do with it.

 

Donbrew,
Sorry for the miss understanding, I did look at the ECM connector and visually did not see anything out of place. I also am not seeing the ground wire connection through the ECM. The information I have shows the ground on the TCM pin 49 going direct to ground at ground point G105. If this is not correct do you have a screen shot of the
ground routing. Hopefully have some time today to ohm a couple cirtuits to see what's going on but being awake still at 2:30 am maybe not.

 

What could cause a ground fault with the car sitting with nothing else done. Did I miss a part where something besides the ECM connector was done between "works" and "don't work"? Occam's razor says whatever changed is the culprit.
Maybe varmints or gremlins got under the hood

So, how many wires do you see on G105? If the wire goes directly there, there should be continuity from the pin, Not much chasing to do.

 

Donbrew,
Sorry but I haven't been able to get back to the ground wire issue yet. I did however get back to the P1174 error. If you remember in the early post I had changed the plugs with the wrong ones, So I pulled the plugs to change which gave a good change to read the 3 week old plugs. The plugs diffenetly showed lean by the charts I could find which lead my decision to change the injectors. With the possibility that it had different injectors in it I pulled them to get the numbers to trace down what I had. I found injector
12602480 which I found to be 2008 model year injectors( I think). The 12602480 number crossed to AC Delco 217-3158 which I was able to found at the local parts stores. So I put the new correct plugs in and new injectors and all seems to be good for now.
The fuel trim number have all come back down and vary around 0 to 3 on long term trim and -3 to 3 on short term trim in steading driving with cruise on. I will apdate on ground when I get back to it but for sure could have been a squirrel as that has happened more times then I care to remember.