New to GM... slightly concerned!

Jake2017AT · February 9, 2020

Hey everyone, new here and new to GMs. I recently purchased a 2017 Sierra AT with the 6.2L and the 8-speed. I love the truck and have been happy with just about everything about it. I purchased the truck knowing that a slight rough idle was “normal” and that the 8 speed is notorious for a hard shift (I have an appointment next week to have the Mobil 1 synthetic trans oil put in). Now the problem is I started throwing a code for cold start, rough idle with a solid CEL (Had it reset at the dealer twice). The last few days, on the first crank of the day, I get a flashing CEL when the truck is coming out of warm up. Turning the truck off and restarting clears the flashing CEL and I go back to the solid one. After researching similar cases, I assume the flashing CEL is most likely an injector malfunction. My main question is if there could be anything else that could cause this issue. Truck only has 19k miles and I can’t believe that a $55k truck (brand new) would have failing injectors with less than 20k miles. The truck is still under Powertrain warranty, but is out of bumper to bumper by 4 months. Thanks all!

davester · February 9, 2020

Get the codes read. They'll at least give you some idea of what's going wrong.

HeySkippyDog · February 9, 2020

Flashing CEL is a major issue. But at 19,000 miles, you shouldn't have ANY CEL at all. That's odd.

Read the codes and see what's going on. These trucks are far too computer-heavy to make a diagnosis on a rough idle symptom alone.

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carnau · February 9, 2020

3 hours ago, Jake2017AT said:

Hey everyone, new here and new to GMs. I recently purchased a 2017 Sierra AT with the 6.2L and the 8-speed. I love the truck and have been happy with just about everything about it. I purchased the truck knowing that a slight rough idle was “normal” and that the 8 speed is notorious for a hard shift (I have an appointment next week to have the Mobil 1 synthetic trans oil put in). Now the problem is I started throwing a code for cold start, rough idle with a solid CEL (Had it reset at the dealer twice). The last few days, on the first crank of the day, I get a flashing CEL when the truck is coming out of warm up. Turning the truck off and restarting clears the flashing CEL and I go back to the solid one. After researching similar cases, I assume the flashing CEL is most likely an injector malfunction. My main question is if there could be anything else that could cause this issue. Truck only has 19k miles and I can’t believe that a $55k truck (brand new) would have failing injectors with less than 20k miles. The truck is still under Powertrain warranty, but is out of bumper to bumper by 4 months. Thanks all!

Check out this thread I posted. It will inform you and give you an idea of how easy it is to replace the injectors if you have to.

JimCost2014 · February 9, 2020

5 hours ago, Jake2017AT said:

Hey everyone, new here and new to GMs. I recently purchased a 2017 Sierra AT with the 6.2L and the 8-speed. I love the truck and have been happy with just about everything about it. I purchased the truck knowing that a slight rough idle was “normal” and that the 8 speed is notorious for a hard shift (I have an appointment next week to have the Mobil 1 synthetic trans oil put in). Now the problem is I started throwing a code for cold start, rough idle with a solid CEL (Had it reset at the dealer twice). The last few days, on the first crank of the day, I get a flashing CEL when the truck is coming out of warm up. Turning the truck off and restarting clears the flashing CEL and I go back to the solid one. After researching similar cases, I assume the flashing CEL is most likely an injector malfunction. My main question is if there could be anything else that could cause this issue. Truck only has 19k miles and I can’t believe that a $55k truck (brand new) would have failing injectors with less than 20k miles. The truck is still under Powertrain warranty, but is out of bumper to bumper by 4 months. Thanks all!

Welcome to the site.

Like posted above, get the codes checked, and start your research on what is actually cover on the powertrain warranty.

Where did you buy the truck, a GM lot? If so, now is a great time to make friends in the service department.

Lsgun1 · February 10, 2020

Flashing CEL just means there's a misfire, not necessarily an injector failure. They shouldn't just be resetting it.

Jake2017AT · February 17, 2020

Just got the call from the dealer (not the one I purchased from). Both codes were attributed to the #4 injector failing. Shop manager said it was covered under warranty but I’m waiting for the call back when he realizes I’m 4 months out of bumper to bumper (although I’m 16k miles under). Truck will be repaired and ready for pick up tomorrow. Seems like an underlying issue if an injector is failing at less than 20k miles....