One problem related to brake light on has been reported for the 2008 Chevrolet Impala. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2008 Chevrolet Impala based on all problems reported for the 2008 Impala.
While driving at 60 mph the cars service traction control light comes on and so does the abs brake service light. The car then reduces power to no more then 35-40 mph and that's with the gas pedal floored. It has happened since new. I have changed out the harness, and wheel hub and it still happens, sometimes in very dangerous situations like while driving on a hwy with a truck behind you and the car goes from 60 mph to 40 mph in a heart beat. The dealership said its a common electrical problem with gm cars in 2006-2009. The only part left to change would be the computer modulator, however talking to other gm owners with the same problem it doesn't seem to help.