P0305 GMC Code - Cylinder 5 Misfire Detected
Quick Answer
A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty spark plug 5, Clogged or faulty fuel injector 5, Faulty ignition coil 5. 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
- P0305 GMC indicates Cylinder 5 Misfire Detected.
- Common causes
- Common causes include Faulty spark plug 5, Clogged or faulty fuel injector 5, Faulty ignition coil 5.
- 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.
Code P0305 GMC Description
What are the Possible Causes of the DTC P0305 GMC?
- Faulty spark plug 5
- Clogged or faulty fuel injector 5
- Faulty ignition coil 5
- Fuel injector 5 harness is open or shorted
- Fuel injector 5 circuit poor electrical connection
- Ignition coil 5 harness is open or shorted
- Ignition coil 5 circuit poor electrical connection
- Insufficient cylinder 5 compression
- Incorrect fuel pressure
- Intake air leak
- Spark Plugs Wires (if equipped)
How to Fix the DTC P0305 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.
Code Tech Notes
There is a Factory Service Bulletins for All 2000-2020 GMC Models:
2000-2020 GMC Factory Service Bulletin OBDII Code P0305
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.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0305 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 P0305 GMC code?
Need more information on how to fix the P0305 GMC code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0305 GMC code diagnosed by a professional: Find a repair shop in your area
Information for Specific GMC Models
- P0305 2014 GMC Sierra — Cylinder 5 Misfire Detected
- P0305 2015 GMC Sierra — Cylinder 5 Misfire Detected
- P0305 2016 GMC Sierra — Cylinder 5 Misfire Detected
- P0305 2017 GMC Sierra — Cylinder 5 Misfire Detected
- P0305 2018 GMC Sierra — Cylinder 5 Misfire Detected
Frequently Asked Questions about P0305 GMC Code
1. What does the P0305 code mean on a GMC?
The P0305 code indicates a misfire has been detected in cylinder 5 of the engine.
2. What are the common symptoms of a P0305 code?
Symptoms may include rough idle, reduced engine performance, poor fuel economy, hesitation during acceleration, and the Check Engine Light turning on.
3. What can cause a cylinder 5 misfire in a GMC?
Common causes include a faulty spark plug, a bad ignition coil, a clogged fuel injector, low cylinder compression, or a vacuum leak near cylinder 5.
4. Can I drive my GMC with a P0305 code?
Driving with a P0305 code is not recommended as it can lead to further engine damage or catalytic converter failure if the misfire persists.
5. How do I fix the P0305 code on my GMC?
Repairs may involve replacing the spark plug or ignition coil for cylinder 5, cleaning or replacing the fuel injector, addressing vacuum leaks, or performing a compression test to check for internal engine issues.
6. How much does it cost to fix a P0305 code?
Costs vary depending on the cause. Replacing a spark plug or ignition coil may cost $100–$300, while more extensive repairs like fixing compression issues could cost significantly more.
7. Can a dirty air filter cause a P0305 code?
While unlikely, a severely clogged air filter can contribute to misfire issues by affecting the air-fuel mixture, but it’s not a common cause specific to cylinder 5.
8. How can I diagnose a P0305 code on my GMC?
Diagnosis typically involves using an OBDII scanner, inspecting the spark plug and ignition coil for cylinder 5, checking the fuel injector, and testing for vacuum leaks or low compression.
9. Can bad fuel cause a P0305 code?
Yes, contaminated or low-quality fuel can cause misfires, including in cylinder 5, by disrupting proper combustion.
10. Will clearing the P0305 code fix the problem?
Clearing the code will turn off the Check Engine Light temporarily, but the underlying issue causing the misfire must be resolved to prevent the code from returning.
Discuss the causes and fixes for P0305 GMC OBDII Code
-
Please include spark plug wire as second in possible causes. I had this code, spark plug was good but the wire was not. Checked resistance on No 5 wire and there was none so I replace all spark plug wires, and the code clear, problem solved.
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