HELP! multiple trans codes!
 

Hello,I have a 2006 hummer h2. I've had it for around 3 months,no problems out of it until recently. Was driving and the engine light started flashing then went steady. It started missing when it was flashing then smoothed back out once steady on. The engine light went off completely on start up for our next drive and drove perfect. Got the old codes checked and it was a random misfire code. Didn't state which cylinders. Then later than evening after getting them checked we filled up on gas,got in started it up and engine light was on again. This time the truck was in limp mode all the way home.like it was stuck in 2nd or 3rd gear. We got home called onstar and had another diagnostic ran and it came back with p0758, p0740, p0785, p2761. I've read it could be a torque converter clutch solenoid causing the other codes? Any help on what this could be would be greatly appreciated as we are supposed to be driving it on a 6-7 hour trip 1 week from today. I can do most of my own work,just need to see what to start with. Also what fuses to check? Thanks in advance!

Have you checked the fluid level? Is it clean or burnt?

If fluid is OK it sounds like an electrical harness issue or ignition switch issue.

Google all your codes at once and you will find some voltage tests.

Tim