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Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 16649
Experience:  GCM master tech over 25 years
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I have a 2006 gmc sierra with a 6.0 engine, I have been

Customer Question

I have a 2006 gmc sierra with a 6.0 engine, I have been getting a p0300 code for awhile now. I changed plugs and wires, fuel pump and maf sensor to no avail, this is a work truck and travels mainly on gravel roads and rarely sees pavement. This work was done at a gm dealer and I just can't afford to take it back anymore, any help would be appreciated
Submitted: 1 year ago.
Category: GMC
Expert:  Gary replied 1 year ago.

just a 300 code ?

when the light comes on do you feel the engine misfire ?

how does it run other than the check engine light ?

if the light did not come on would you know there was anything wrong ?

Customer: replied 1 year ago.
Engine misfires and stalls when engine light comes on sometimes it won't restart, it has left me stranded twice now
Expert:  Gary replied 1 year ago.

is there any chance when it would not restart was it tested for spark when cranking it over ?

would it somewhat run on starting fluid being sprayed into the throttle body butter fly ?

Customer: replied 1 year ago.
I have not tried that and I don't think the dealer did either , I also failed to mention that the battery has been replaced as well
Expert:  Gary replied 1 year ago.

when this will not start and the engine physically cranks over it is missing spark or fuel

and once we know which we are missing it will narrow down the problem area

Customer: replied 1 year ago.
I also have an otc scan tool with monitor and freeze frame capabilities, but I'm not sure what im looking for when im watching the numbers, what are some tattletales I can watch for
Expert:  Gary replied 1 year ago.

get it to act up and not start see on the live data when cranking it over if there is a crank RPM registering

see if the engine will somewhat run on starting fluid and also check for spark out of the coils when cranking it over

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