A co worker of mine has a pontiac g6 that will randomly die whether it is while driving or sitting in a parking lot…when it shuts down it flashes the mesage engine power reduced/engine power disabled. . It has been to the dealer several times and still cannot figure it out. IM assuming since it is a gm it is a common problem and someone will know something.
Which motor? Assuming 3.5L which is most common, but 3.6L and 3.9L V6 were also possible.
Also, google “engine power reduced/engine power disabled” and you’ll get a lot of others with the same issue. the 3.5L was used in the Impala, malibu, G6, Aura, and more so plenty to look for.
Sounds like a few possible issues. Could be a communication issue or an issue with the drive by wire throttle. That message usually accompanies those kinds of problems. Good luck.