Hummer H2 2007. DTC p0300 what does it mean?

Question

Engine was overhaul a week ago.all gaskets and o-rings were change.intake and exhaust valves are new.piston and rings are new.

Answer 1

P0300 means there is a misfire, you will have to go through the list below to see what the problem is

Possible causes

- Faulty spark plug (s) 

- Faulty ignition coil (s) 

- Clogged or faulty fuel injector (s)

- Intake air leak

- Fuel injectors harness is open or shorted

- Fuel Injectors circuit poor electrical connection

- Ignition coils harness is open or shorted

- Ignition coils circuit poor electrical connection

- Insufficient cylinders compression

- Incorrect fuel pressure