P0300 Chevrolet -

Question

I have a 2002 chevy van 3500 with a po300 code seems to idle a little ruff but engine light flashes only on highway

Answer 1

P0300 Random misfire

Check the ignition system , this is more of a ignition related especially when it flashes at highway speed. what happens is the the sparkplug wire tend to seek ground and cause the misfire .So a full tune up of  sparkplug and wire and maybe ignition coil