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
– 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
Tech notes
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see “Possible Causes”.
There is a factory service bulletin for the following GMC models:
2000-2008 GMC Sonoma
2000-2008 GMC Sierra
2000-2008 GMC Yukon
2000-2008 GMC Yukon XL
2001-2008 GMC Denali
2001-2008 GMC Denali XL
2001-2008 GMC Savana
2002-2008 GMC Envoy
2002-2008 GMC Safari
2002-2008 GMC Jimmy
2000-2008 GMC Factory Service Bulletin OBDII Code P0300
When is the code detected?
The control module monitors the crankshaft speed and has detected a misfire condition
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Lack/loss of power
– Hard start
– Engine hesitation
– Lack/loss of power
– Hard start
– Engine hesitation
P0300 GMC Description
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.
GMC Technical Service Bulletins for P0300 code
2008 GMC CANYON ENGINE AND ENGINE COOLING:ENGINE
2009 GMC CANYON ENGINE AND ENGINE COOLING:ENGINE
2008 GMC ENVOY ENGINE AND ENGINE COOLING:ENGINE
2009 GMC ENVOY ENGINE AND ENGINE COOLING:ENGINE
2010 GMC TERRAIN ENGINE AND ENGINE COOLING:ENGINE
2010 GMC TERRAIN ELECTRICAL SYSTEM
2010 GMC ACADIA ENGINE AND ENGINE COOLING:ENGINE
2010 GMC ACADIA ELECTRICAL SYSTEM:WIRING
2011 GMC ACADIA ENGINE AND ENGINE COOLING:ENGINE
2011 GMC ACADIA ELECTRICAL SYSTEM:WIRING