AutoCodes – Generic – P0679

P0679 Code - Cylinder 9 Glow Plug Circuit Fault

Quick Answer

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. Common causes include Faulty cylinder #9 glow plug, Cylinder #9 glow plug harness is open or shorted, Cylinder #9 glow plug circuit poor electrical connection. 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: P0679 indicates Cylinder 9 Glow Plug Circuit Fault.
Common causes: Common causes include Faulty cylinder #9 glow plug, Cylinder #9 glow plug harness is open or shorted, Cylinder #9 glow plug circuit poor electrical connection.
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 4,585

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on May 05, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0679 Description

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The Engine Control Module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage. The California Glow Plug system has eight individual glow plug supply circuits between the controller and the glow plugs. If the feedback voltage from the controller to the ECM is not within range, the ECM sets the OBDII code.

OBDII Code P0679 - Cylinder 9 Glow Plug Circuit Fault - AutoCodes.com — P0679 Code - Cylinder 9 Glow Plug Circuit Fault

What does this mean?

What are the Possible Causes of the DTC P0679?

Faulty cylinder #9 glow plug
Cylinder #9 glow plug harness is open or shorted
Cylinder #9 glow plug circuit poor electrical connection
Faulty glow plug module

How to Fix the DTC P0679?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0679 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 P0679 code?

Need more information on how to fix the P0679 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0679 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P0679 Volkswagen — Cylinder 9 Glow Plug Circuit Fault

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 P0679 Code

1. What are common symptoms of OBDII code P0679 (Cylinder 9 Glow Plug Circuit Fault)?

- Common symptoms include hard starting, rough idling, decreased fuel efficiency, and the illumination of the check engine light.

2. What are possible causes of OBDII code P0679?

- Possible causes include a faulty glow plug in cylinder 9, damaged wiring or connectors in the glow plug circuit, or a malfunctioning glow plug control module.

3. How can I diagnose the cause of OBDII code P0679?

- Diagnosing the issue involves using a multimeter to test the resistance of the glow plug, inspecting the wiring for damage, and checking the glow plug control module for proper functioning.

4. Can I still drive my vehicle with OBDII code P0679?

- It is not recommended to drive the vehicle with this code as it can lead to poor engine performance and potential damage over time. It is best to address the issue promptly.

5. What are the repair options for OBDII code P0679?

- Repair options include replacing the faulty glow plug in cylinder 9, repairing any damaged wiring or connectors, or replacing the glow plug control module if necessary.

6. Are there any preventive maintenance tips to avoid OBDII code P0679 in the future?

- Regularly inspecting and testing the glow plugs in all cylinders, ensuring proper maintenance of the glow plug circuit components, and using high-quality diesel fuel can help prevent this issue.

7. Can weather conditions affect the occurrence of OBDII code P0679?

- Yes, extreme cold weather can put more strain on the glow plug system, potentially leading to issues like cylinder 9 glow plug circuit faults. Properly functioning glow plugs are crucial in cold climates.

8. How long does it typically take to repair OBDII code P0679?

- The repair time can vary depending on the exact cause of the issue and the extent of the repairs needed. On average, it may take a few hours to a full day for a mechanic to address the problem.

9. Can OBDII code P0679 affect the overall performance of my vehicle?

- Yes, if left unresolved, OBDII code P0679 can impact the performance of your vehicle, leading to issues such as reduced power, increased emissions, and potential engine damage.

10. Is it necessary to clear the OBDII code P0679 after the repairs are completed?

- Yes, it is important to clear the code using an OBDII scanner after the repairs to reset the system and ensure the issue has been successfully addressed.