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P0300 GMC Code - Engine Misfire Detected

- Code Popularity: 246,822 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0300 GMC?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other 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
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How to Fix the DTC P0300 GMC?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code 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 a common cause of multi-cylinder misfiring. If no leak is found, the next step is to replace the spark plugs. If the problem persists, more tests need to be done to diagnose the problem, see "Possible Causes".

There are Factory Service Bulletins for the following GMC models:

All 2000-2013 GMC Models:
2000-2013 GMC Factory Service Bulletin OBDII Code P0300

2014 GMC Sierra 1500
2015-2016 GMC Sierra
2015-2016 GMC Yukon
2015-2016 GMC Yukon XL
GMC Factory Service Bulletin OBDII Code P0300

2005-2006 GMC Envoy Models
2007 GMC Yukon, Yukon Denali, Yukon XL Denali, Yukon XL with 5.3L or 6.0L Vortec V8 Engine
GMC Factory Service Bulletin OBDII Code P0300

2000-2020 GMC All Models
2000-2020 GMC Factory Service Bulletin OBDII Code P0300
This Factory Service Bulletin explains how this condition may be caused by significant carbon build up on the intake and/or exhaust valves due to fuel contamination or incomplete burning of the fuel.





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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0300 GMC code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • Lack/loss of power
  • Hard start
  • Engine hesitation

Code P0300 GMC Description

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. The Engine Control Module (ECM) is able to detect these variations by closely monitoring the crankshaft position sensor signal. The signals of the camshaft position sensors are used to determine which cylinder is misfiring. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, the Diagnostic Trouble Code (DTC) will be set. Under certain driving conditions, a misfire rate can be high enough to cause the catalytic converter to overheat, possibly damaging the converter. The Malfunction Indicator Lamp (MIL) flashes when the converter is overheating, damaging conditions are present, and the DTC is set. The DTC will be set when the ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed a predetermined value or a misfire rate high enough to cause catalyst damage.

OBDII Code P0300 GMC - Engine Misfire Detected - AutoCodes.com
P0300 GMC Code - Engine Misfire Detected

Need More Information on the Code?

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