AutoCodes - Gmc - P0306 GMC

P0306 GMC Code - Cylinder 6 Misfire Detected

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3
Table of contents

|P0306 GMC code possible causes

  • Faulty spark plug 6
  • Clogged or faulty fuel injector 6
  • Faulty ignition coil 6
  • Fuel injector 6 harness is open or shorted
  • Fuel injector 6 circuit poor electrical connection
  • Ignition coil 6 harness is open or shorted
  • Ignition coil 6 circuit poor electrical connection
  • Insufficient cylinder 6 compression
  • Incorrect fuel pressure
  • Intake air leak

|How do I fix the P0306 GMC code?

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's pins.

|P0306 GMC code tech notes

The P0306 code means that the cylinder 6 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 6. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".

There is a Factory Service Bulletins for All 2000-2018 GMC Models:
2000-2018 GMC Factory Service Bulletin OBDII Code P0306
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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|Cost of diagnosing the P0306 GMC code

Labor: 1.0

The cost of diagnosing the P0306 GMC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.

|What are P0306 GMC code possible symptoms?

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

|P0306 GMC code description

The Engine Control Module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when an engine cylinder misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM can detect individual cylinder misfire events.
Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. The Diagnostic Trouble Codes (DTC) P0306 correspond to cylinders 6. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set, and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM. In Spark Ignition Direct Injection (SIDI) system applications, if a fuel injector fault DTC is set during a misfire event, the ECM will not re-enable the injector.
OBDII Code P0306 Gmc - Cylinder 6 Misfire Detected - AutoCodes.com

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|P0306 GMC code comments

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