Engine power reduced???

I was driving on the highway to work this morning when all of the sudden I my Impala slows down. I look at the dash and it says "engine power reduced" What does this mean?

The pcm sees a misfire or other operating anamoly that causes it to reduce operating power to save the engine or catalytic convertor, should be a code stored, get it scanned.

That usually happens when there is a TAC code set from the throttle body....

If you buy the trottle body from autozone do the sensors have to be reprogrammed? Or does it come already set?

sometimes the check engine signal comes on-then later the message that service traction control and engine power reduced comes on, and the car slows and is hard to accelerate-but does not happen all the time-how do I fix without paying an arm& leg at a dealer??

What car is this? Have you had it scanned?

I am sorry for jumping in-my first time on the site-2008 Impala v6
I was told it was the throttle sensor-but had to replace the whole unit

Again what was the code, we cannot begin to help you with no info to work from.