Flashing service engine message and engine misfires when driving up hill

Good morning,

This could be plugs and/or ignition coils causing the misfire.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

The light flashing indicates there is a misfire or one or more of the cylinders are not providing enough power.

https://www.2carpros.com/articles/how-to-change-spark-plugs

I would also do a compression test since the plugs are out to be sure there is no internal engine issue. You can rent a tester at a parts store. You should have 140-160 pounds on each cylinder.

https://www.2carpros.com/articles/how-to-test-engine-compression

Roy