Question

2003 Chevrolet Express 2500 6.0L with engine code P0300. Cylinder Misfire Detected Random Cylinders and engine-light flashing

Answer 1

P0300 Random misfire

Random misfire means more than 2 cylinders. Random misfire are mostly from ignition leaking secondary ignition towards ground, which may require a full tune up with sparkplug wires and sparkplugs.This can also be from vacuum leaks that can also cause random misfire

Answer 2

P0300 Chevrolet Code - Engine Misfire Detected
Read more: https://www.autocodes.com/p0300_chevrolet.html