2014 Sierra won’t fire after transmission rebuild

[thedream craftlife]

I had a local transmission shop rebuild the transmission on my 2014 Sierra 4.3. The engine ran when I had it towed to the shop. After the rebuild they said it wouldn’t fire. They said they do not program the tecm til the engine runs and haven’t added fluid. The spark plugs were really bad so they put new one, changed the engine oil and filter, put new rocker gaskets and a new brake vacuum pump. Said the engine is worn out (283,000) miles. It ran before it was sent to the shop. I am going to tow it home and work to figure it out. Any ideas of what can be wrong is really appreciated. Thank! George

[davester]

They disconnected something and didn't reconnect it, and/or pinched some wires somewhere, and/or the battery is dead, and/or they did try to flash the transmission computer and somehow botched the job badly (as you can flash the trans computer w/o the engine being capable of running).

 

[thedream craftlife]

Does the engine start and run without the transmission computer being flashed. I also heard that if the transmission computer and battery were disconnected it would cause a logic lock in the ecm which will keep the engine from firing. Supposedly disconnecting the positive and negative battery cables and holding them together will solve this logic lock.