If you have ABS it could be in need of brake pads. Worn brake pads make for low brake fluid which makes for ABS warning which make for reduced power.

 

I keep a code reader in my HHR for that reason, they are not that expensive I bought mine from Wal-Mart they matched the price I got from Amazon $82.00, now that I have it in my car I never get a code Karma I guess.