Engine-Codes - Hummer - P0300 Hummer

P0300 Hummer Code - Engine Misfire Detected

- Code Popularity: 73,906 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0300 Hummer?

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

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 commonly caused by 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 is a Factory Service Bulletin for the following HUMMER models:
2003-2008 HUMMER H2
2006-2008 HUMMER H3
2003-2008 HUMMER Factory Service Bulletin OBDII Code P0300





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How to Fix the DTC P0300 Hummer?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Search for P0300 Hummer Questions and Answers: Search here →

What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P0300 Hummer code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops 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

What Does the P0300 Hummer Code Mean?

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.

P0300 Hummer Code - Engine Misfire Detected

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