2018 Chevy Malibu - battery dead, swapped battery, now saying 'engine reduced power'

We went out to start the car, and it showed several warnings that the battery was dead before shutting off. After swapping in a new battery, the check engine light came on. We thought driving it a bit would help recalibrate, but about 3 miles down the road, it suddenly slowed way down, barely crawling up a hill, with the dash warning reading ‘engine reduced power.’ We just took it out two days ago, and everything was fine—no warnings or weird driving issues. The battery probably drained because it was old and it got cold this weekend. The car has only 61,000 miles on it, and we’re the only owners. It was inspected in August with no issues. We’re calling the mechanic tomorrow, but wanted to see if anyone else has experienced this.

I’d check your charging system; maybe the alternator isn’t working properly.

Second this! It happened to my Impala, and it turned out to be the alternator.

That sounds frustrating! Wouldn’t there have been some kind of warning about the alternator before this happened?

Tobi said:
That sounds frustrating! Wouldn’t there have been some kind of warning about the alternator before this happened?

Not always. Sometimes they fail without prior warning, especially if they’re old.

Definitely get the alternator checked. If it’s not charging the battery, you’ll keep running into issues.

Also, make sure to check the battery connections. Sometimes a loose connection can cause weird issues like this.