P0300 GMC -

Question

Had water in fuel. Drained tank and dried it out. Cleared fuel line's. But getting a code p0300 don't know what to do now ?

Answer 1

P0300 is a misfire code, if you have water in the tank that mean the injectors might have got affected.

I would try to use a good fuel system cleaner like 3M or BG 44k, if you have not replace/checked the spark plug you should also do that.