That means the engine is overheating. Check in this ORDER.
First check coolant level in radiator, if low then Find and FIX the LEAK and refill the system with COOLANT. Check engine FAN clutch, Thermostat, Radiator making sure it is NOT stoped up. You will find your problem in these AREA.
What does reduce engine power means?
The 2003 Chevrolet Silverado-1500 has a V6 engine.
The 2003 Chevrolet Silverado-2500HD has a V8 engine.
The 2003 Chevrolet Silverado-2500HD has a 6.0 L base engine size.
The 2003 Chevrolet Silverado-1500 has a 4.3 L base engine size.
The 2003 Chevrolet Silverado-2500HD's engine produces 300 hp @ 4400 rpm.
Yes same engine.
The 2003 Chevrolet Silverado-1500's engine produces 200 hp @ 4600 rpm.
The 2003 Chevrolet Silverado-2500HD's engine produces 360 ft-lbs. @ 4000 rpm.
Time to buy a new car.
Under the engine
The 2003 Chevrolet Silverado-1500's engine produces 260 ft-lbs. @ 2800 rpm.