That means the engine is over heating / running hot for some reason.
Check thermostat, Coolant level in radiator, check for coolant leak on engine somewhere. Fix and repair as needed.
im having the same problem with my 03 silverado check this out link out for your answer http://www.ssrfanatic.com/forum/f5/tsb-reduced-engine-power-15539/
The 2008 Chevrolet Silverado-2500HD has a V8 engine.
The 2008 Chevrolet Silverado-3500HD has a V8 engine.
The 2008 Chevrolet Silverado-1500 has a V6 engine.
It can be 1 out of 150 different reasons. just get it towed!
The 2008 Chevrolet Silverado-1500 has a 4.3 L base engine size.
The 2008 Chevrolet Silverado-2500HD has a 6.0 L base engine size.
The 2008 Chevrolet Silverado-3500HD has a 6.0 L base engine size.
The 2008 Chevrolet Silverado-2500HD's engine produces 353 hp @ 5400 rpm.
The 2008 Chevrolet Silverado-3500HD's engine produces 353 hp @ 5400 rpm.
The 2008 Chevrolet Silverado-3500HD's engine produces 373 ft-lbs. @ 4400 rpm.
The 2008 Chevrolet Silverado-1500's engine produces 195 hp @ 4600 rpm.