2020 Terrain stalled

[Sheryl Ann]

I have a 2020 GMC Terrain SLT w/ about 9000 miles on it that I purchased in February. On the morning of 9/3/20 when I started it, it stalled after a few seconds. I tried it 3 more times a few minutes apart and it stalled within a few seconds each time. After the 3rd attempt the check engine light came on so I stopped trying to start it. About 10 minutes later I get a txt from OnStar saying “Diagnostic Alert: Service the engine and transmission system in your 2020 Terrain within 1 day.” Anyway that day my husband gets home from work in the afternoon and calls me to tell me the check engine light isn’t on and it started right up and sounds fine. Pretty sure he thought I was crazy but he had it towed to GMC dealer anyway to get it checked out. The GMC mechanic did some diagnostics and found “code P12A6 in ECM for internal hardware damage”. Long story short they “replaced and programmed” the ECM and gave me my car back. Now 3.5 weeks later I’m in reverse pulling out of my driveway, onto a busy main road mind you, and when I press the D button to put it in drive it stalls in the middle of the street. It wasn’t a rough idle type of stall if you know what I mean, it legit just shut off, like the power cut off as if I had pressed the engine stop button. It scared the ****** out of me. Anyway i was immediately able to start it and it sounded fine. It seems fine now... I’ve been driving around all day, start/stopped it multiple times today, but I’m petrified it will happen again. No check engine light or anything came on. My question is, if I take it in to the dealer again are they even going to be able to figure it out since no warnings appeared? Is there specific wording I should use to describe the situation? I have a 2 year older and am literally petrified to drive this car now.. what if it just shuts off again?

Edited September 27, 2020 by 99silveradoz71
Typo

[dsr611]

Take it back to the dealer...if they can't duplicate the issue (or pull codes that may be stored) at least it will be on record in case it does it again.