p0300 code on 2001 chevy tahoe only when i pull a trailer engine lite comes on

Question

the check engine light only come on when I am
pulling a trailer at speeds of 55mph or higher truck seems to be running ok no misfires or stalling or anything like that, when Im not pulling a trailer I never seem to get the check engine light. anybody got any ideas?

Answer 1

When you tow a trailer this is where the ignition coil secondary ignition are in greater demands, check the sparkplugs, worn sparkplug wire can also cause this type of condition

​Here a same year make and model, it misfire only when a horse trailer was attached, there was no misfire code or misfire at idle, but very intermittently there was misfire condition, The problem was found when at idle the sparkplug was seen jumping in its cylinder, the fix torque the sparkplug , in your case check the sparkplug for any  being loose