2021 1500 2.7 weird issues

Tigerbend225 · December 23, 2021

Hello all, thought I would share some problems I have recently started having with my truck and curious if anyone else has seen or heard of these problems. I have a 2021 1500 custom with the 2.7 and absolutely love this motor and truck but earlier this month I started the truck like normal and pulled about 10ft and felt loss of power and a strong vibration. I got all kinds of codes and lights pop up including CEL, service brake, traction control turned off, serve TCM. I noticed the indication for the shifter was gone and the truck would barely drive. It would slam in reverse when I would try to cycle the shifter. When I turned it off and restarted it acted the same. I noticed I could not get my key to go all the way back when off so it would not come out. It would drive but never shift like it was in limp mode. I pulled up to a safe spot and turned the truck off again. Looked over battery and fuses then tried cranking again and nothing would happen. 2hours later when tow got there, truck cranks right up like normal. Got it towed to dealer and they said it was wiring harness problems and ordered parts. Fast forward 2 weeks they call and say everything is good to go. Pick the truck up and not even 1/4 mile down the road I stop at a red light and bam, all the same lights and codes pop up. Same problems I had before but this time I could hear a slight grinding noise under the truck. Get it towed once again to dealer and truck still would not crank for them. Next day they tell me they have a torque convertor on order. Got the truck in May and only have 11k miles on it and have never had an issue with it until now. Sorry for the long post.

jpogue · December 23, 2021

My son in law had a problem that sounds like yours. He had a custom with the 2.7. The dealer never could fix it and finally replaced his truck. He had about 1500 miles on it. They tried several things, including the wiring harness, but never found anything that worked.

customboss · December 23, 2021

They didn't find all the chafing areas and repair. Hope this link helps you get help. I have a 2022 LTD and I am inspecting that they corrected these contact points myself.

https://gm-techlink.com/?p=15518

newdude · December 23, 2021

1 hour ago, Tigerbend225 said:

Hello all, thought I would share some problems I have recently started having with my truck and curious if anyone else has seen or heard of these problems. I have a 2021 1500 custom with the 2.7 and absolutely love this motor and truck but earlier this month I started the truck like normal and pulled about 10ft and felt loss of power and a strong vibration. I got all kinds of codes and lights pop up including CEL, service brake, traction control turned off, serve TCM. I noticed the indication for the shifter was gone and the truck would barely drive. It would slam in reverse when I would try to cycle the shifter. When I turned it off and restarted it acted the same. I noticed I could not get my key to go all the way back when off so it would not come out. It would drive but never shift like it was in limp mode. I pulled up to a safe spot and turned the truck off again. Looked over battery and fuses then tried cranking again and nothing would happen. 2hours later when tow got there, truck cranks right up like normal. Got it towed to dealer and they said it was wiring harness problems and ordered parts. Fast forward 2 weeks they call and say everything is good to go. Pick the truck up and not even 1/4 mile down the road I stop at a red light and bam, all the same lights and codes pop up. Same problems I had before but this time I could hear a slight grinding noise under the truck. Get it towed once again to dealer and truck still would not crank for them. Next day they tell me they have a torque convertor on order. Got the truck in May and only have 11k miles on it and have never had an issue with it until now. Sorry for the long post.

Got a list of any of the codes they found?

Tigerbend225 · December 27, 2021

No I do not have a list of codes at the moment. When I get them I'll post on here. They told me the computer will not talk to the torque convertor module after an attempt to reprogram, so they are waiting for a new module to come in. This will be this dealers second attempt to fix the problem. guess ill get it towed to another if they can not figure out the problem. At what point should I contact GM about it since this is attempt #2 and almost 30 days in the shop.

newdude · December 27, 2021

3 minutes ago, Tigerbend225 said:

No I do not have a list of codes at the moment. When I get them I'll post on here. They told me the computer will not talk to the torque convertor module after an attempt to reprogram, so they are waiting for a new module to come in. This will be this dealers second attempt to fix the problem. guess ill get it towed to another if they can not figure out the problem. At what point should I contact GM about it since this is attempt #2 and almost 30 days in the shop.

Dumb question but a valid one. Any modifications to the truck? Aftermarket devices like a speedo calibrator?

Tigerbend225 · December 27, 2021

No sir. Truck is stock with no after market mods.

Tigerbend225 · December 31, 2021

Just an update. Picked my truck up today. They replaced the TCM and did a reprogram. Drove home and the truck did fine so I'm happy and hopeful no more issues. The code they were getting is U0100 when they diagnosed it.

Tucker · February 4, 2022

On 12/23/2021 at 12:32 PM, customboss said:

They didn't find all the chafing areas and repair. Hope this link helps you get help. I have a 2022 LTD and I am inspecting that they corrected these contact points myself.

https://gm-techlink.com/?p=15518

Was just looking at the techlink. Someone posted end Jan. still an issue on some of the 2022's with the 2.7. Good idea to give this techlink a lookup.

matienzone · February 9, 2022

I'm at around 2500 miles so far, drove it off the lot 12/31/22. I bought the 2.7L Custom LTD. Now that I've read over this thread, it really makes me thing about the few times that my 2.7 custom shifted really hard into second gear or when shifting into reverse. It's been pretty random. I did also notice this afternoon while rolling in traffic that there was some slight hesitation and jerking for a second or two...