BlackPAAT4
New member
First, I love my AT4. I am typing this to help others until GM decides to put out a service bulletin or a recall on the problem. The only reason I put up with this is because I travel a great deal and was able to leave the truck at the dealer for extended periods of time. This is a brand new 2023 1500 AT4, 3.0 Diesel. Ordered in August 2022, received Jan 2023. What happened each time was the craziest thing I ever saw. Usually at a stop sign then accelerate or on a turn at speed suddenly everything in the truck would reset, check engine light, full dash reset, even turned the heater fan on, transmission warnings, on and on and on and on. The first time it happened it scared the hell out of me, left me dead in an intersection in Philadelphia. Horns beeping all around me, and people yelling. Turn it off/on and I can get it to move in a kind of limp mode. I drove it home at 20 MPH, it would only shift to 2nd or 3rd gear. The thing is re-setting all the way.
I get it to the dealer, they call the next day and tell me and I quote "We cant help you. The truck has too many error codes. We reset it and cannot get it to happen again, sorry." They basically ask me to take it home and let them know if it happens again. To make a long story short I had the truck back to the dealer 4 times 1st time, 1 week. 2nd time 2 weeks. 3rd time 3 weeks, 4th time 3 weeks. In between I can only test the truck on the weekends because I travel during the week. They would drive it for hours and hours trying to reproduce the problem, They put a lot of miles on the truck, guessing over 1400. They replaced many, many parts, transmission control module, brake control module, etc. They pulled the truck appart, dash, everything, connected/reconnected as much as they could find. Had a GM local field engineer out several times - tons of recommendations. Still failed after various amounts of time. There is much more to this story, not worth typing.
The problem and the fix:
Bottom line the issue was a wiring harness on the Diesel versions of the AT4, maybe others, that is pulled too tight around the engine block and the alternator bracket. Truck/engine motion wears away the cloth wrap. This happened to me in under 400 miles the first time. Digs into the wires and causes a short. In my case it dug into the white, main communications wire and shorted the communications between all the computers on the truck and it went crazy. The only reason they found it was because they had what I think is a 2023 Denali Diesel with the same issue and through pure dumb luck stumbled across the issue. They then checked mine and found the exact problem. I can understand how it was missed, There is only a pin hole visible and it is buried. To correct the problem they go through the wheel well and because it is a communications wire have a special procedure to repair it.
I am hoping this post helps someone else if they are experiencing strange electrical problems. I was told there are more trucks out there with the same issue. I let them hold onto my truck for an extra few days so GM can come back out, document the problem, examine the repair and re-routing of the wiring harness, then later decide what to do in the future. Pictures below.
I get it to the dealer, they call the next day and tell me and I quote "We cant help you. The truck has too many error codes. We reset it and cannot get it to happen again, sorry." They basically ask me to take it home and let them know if it happens again. To make a long story short I had the truck back to the dealer 4 times 1st time, 1 week. 2nd time 2 weeks. 3rd time 3 weeks, 4th time 3 weeks. In between I can only test the truck on the weekends because I travel during the week. They would drive it for hours and hours trying to reproduce the problem, They put a lot of miles on the truck, guessing over 1400. They replaced many, many parts, transmission control module, brake control module, etc. They pulled the truck appart, dash, everything, connected/reconnected as much as they could find. Had a GM local field engineer out several times - tons of recommendations. Still failed after various amounts of time. There is much more to this story, not worth typing.
The problem and the fix:
Bottom line the issue was a wiring harness on the Diesel versions of the AT4, maybe others, that is pulled too tight around the engine block and the alternator bracket. Truck/engine motion wears away the cloth wrap. This happened to me in under 400 miles the first time. Digs into the wires and causes a short. In my case it dug into the white, main communications wire and shorted the communications between all the computers on the truck and it went crazy. The only reason they found it was because they had what I think is a 2023 Denali Diesel with the same issue and through pure dumb luck stumbled across the issue. They then checked mine and found the exact problem. I can understand how it was missed, There is only a pin hole visible and it is buried. To correct the problem they go through the wheel well and because it is a communications wire have a special procedure to repair it.
I am hoping this post helps someone else if they are experiencing strange electrical problems. I was told there are more trucks out there with the same issue. I let them hold onto my truck for an extra few days so GM can come back out, document the problem, examine the repair and re-routing of the wiring harness, then later decide what to do in the future. Pictures below.
