CEL and reduced power lights on

Hello, I am fairly new to the forum guys. I don't understand a whole lot about these trucks so maybe yall have some insight. My wife's 02 TB had both the CEL and the reduced power light come on this morning on the way to work. Onstar wasnt working (faulty equip) so we have to wait to get it to a dealer. Is there anything that is indicative of both of those lights coming on at the same time? If anyone has any info I would appreciate it. Thanks.

Welcome to the site.
Sorry, no experience with the TB.
Never heard of a reduced power light before.

Thanks for the response. I ended up taking it to the dealer. It was the throttle sensors that were off. The reduced power mode comes on when the car is doing something that could harm it further if run at full power. New thing I guess. Bunch of things can cause it to come on like the ABS or throttle problems.