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AutoCodes – GMC – P0301 GMC

P0301 GMC Code - Cylinder 1 Misfire Detected

Quick Answer

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty Spark Plug #1, Clogged or faulty Fuel Injector #1, Faulty Ignition Coil #1. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0301 GMC indicates Cylinder 1 Misfire Detected.
Common causes
Common causes include Faulty Spark Plug #1, Clogged or faulty Fuel Injector #1, Faulty Ignition Coil #1.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
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Code Popularity 48,552
How popular is this code, among other codes? Medium
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Table of contents Created and updated by William Orellana on Jul 17, 2023
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Code P0301 GMC Description

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. The Engine Control Module (ECM) can 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, 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 single-cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.
OBDII Code P0301 GMC - Cylinder 1 Misfire Detected - AutoCodes.com
P0301 GMC Code - Cylinder 1 Misfire Detected
What does this mean?

What are the Possible Causes of the DTC P0301 GMC?

  • Faulty Spark Plug #1
  • Clogged or faulty Fuel Injector #1
  • Faulty Ignition Coil #1
  • Fuel Injector #1 harness is open or shorted
  • Fuel Injector #1 circuit poor electrical connection
  • Ignition Coil #1 harness is open or shorted
  • Ignition Coil #1 circuit poor electrical connection
  • Insufficient cylinder 1 compression
  • Incorrect fuel pressure
  • Intake air leak

How to Fix the DTC P0301 GMC?

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

What does this mean?

Code Tech Notes

The P0301 code means that cylinder 1 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 1. 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 2000-2020 GMC Models:
2000-2020 GMC Factory Service Bulletin OBDII Code P0301
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 P0301 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0301 GMC code?

Need more information on how to fix the P0301 GMC code? Get Access to Factory Service Manuals

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Get the P0301 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0301 GMC Code

1. What are the common symptoms of OBDII code P0301 (Cylinder 1 Misfire Detected)?

- Common symptoms include engine misfiring, rough idling, loss of power, and potential increase in fuel consumption.

2. What are the typical causes of a P0301 code in a GMC vehicle?

- Causes can include faulty spark plugs, ignition coils, fuel injectors, vacuum leaks, low compression in cylinder 1, or issues with the engine control module.

3. How can I diagnose the source of the misfire in cylinder 1?

- Diagnosis often involves inspecting spark plugs, ignition coils, fuel injectors, and conducting a compression test on cylinder 1 to identify the root cause of the misfire.

4. Can driving with a P0301 code cause further damage to the vehicle?

- Continuing to drive with a misfire can potentially damage the catalytic converter and other engine components, leading to more costly repairs over time.

5. What are some DIY repair tips for addressing a P0301 code in a GMC?

- DIY repair tips include checking and replacing spark plugs, testing and swapping ignition coils, inspecting for vacuum leaks, and ensuring proper fuel delivery to cylinder 1.

6. Is it safe to drive my GMC with a P0301 code if the engine is running smoothly?

- It is not recommended to drive with a persistent misfire, even if the engine seems to be running smoothly at times, as it can still lead to long-term damage.

7. How much does it typically cost to repair a Cylinder 1 Misfire Detected issue in a GMC vehicle?

- The cost of repairs can vary depending on the exact cause of the misfire, but it may range from $100 for spark plug replacement to several hundred dollars for more complex repairs.

8. Can bad gasoline quality cause a Cylinder 1 Misfire Detected code?

- Yes, poor quality gasoline or contaminated fuel can potentially lead to misfires, including triggering a P0301 code in cylinder 1.

9. Will resetting the OBDII code make the issue go away permanently?

- Simply resetting the code will not fix the underlying problem causing the misfire. It is essential to diagnose and address the root cause to prevent the issue from recurring.

10. Should I seek professional help for diagnosing and repairing a P0301 code in my GMC?

- It is recommended to consult a qualified mechanic or technician to accurately diagnose and repair a Cylinder 1 Misfire Detected issue, especially if you are not experienced with automotive repairs.

1. What are the common symptoms of OBDII code P0301 GMC (Cylinder 1 Misfire Detected)?

- Common symptoms include engine misfiring, rough idling, loss of power, and potential fuel efficiency issues.

2. What are the possible causes of OBDII code P0301 GMC?

- The code may be triggered by issues such as a faulty spark plug, ignition coil, fuel injector, vacuum leak, or low compression in cylinder 1.

3. How can I diagnose the cause of OBDII code P0301 GMC?

- Diagnosis typically involves inspecting spark plugs, ignition coils, fuel injectors, vacuum lines, and performing a compression test on cylinder 1.

4. Can a dirty or clogged fuel injector cause OBDII code P0301 GMC?

- Yes, a dirty or clogged fuel injector in cylinder 1 can disrupt the air-fuel mixture, leading to a misfire and triggering the code.

5. How should I go about repairing OBDII code P0301 GMC?

- Repair steps may include replacing spark plugs, ignition coils, fuel injectors, addressing vacuum leaks, or performing a compression test to identify any engine issues.

6. Is it safe to continue driving with OBDII code P0301 GMC present?

- It is not recommended to drive with a misfire as it can cause further damage to the engine and components. Immediate attention and repair are advised.

7. Can weather conditions affect the occurrence of OBDII code P0301 GMC?

- Extreme weather conditions, such as very cold temperatures, can potentially exacerbate existing issues leading to a cylinder 1 misfire.

8. Will resetting the OBDII code P0301 GMC make the issue go away?

- Simply resetting the code without addressing the root cause will not fix the underlying problem. It is important to diagnose and repair the issue causing the misfire.

9. Can a bad ignition coil cause OBDII code P0301 GMC?

- Yes, a faulty ignition coil in cylinder 1 can result in a weak spark, leading to a misfire and the triggering of the P0301 code.

10. How can regular maintenance help prevent OBDII code P0301 GMC from occurring?

- Regular maintenance, including timely spark plug replacements, fuel system cleaning, and periodic engine inspections, can help prevent issues that may lead to cylinder misfires and the associated OBDII code.

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