P0679 OBD Error Code: Problem & Solutions

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Are you experiencing diminished fuel efficiency? Is your engine giving issues during cold start? Is the car engine stalling and losing acceleration? All these can be the indication of OBD Code P0679.

The P0679 diagnostic trouble code is an indication that there is an issue with the cylinder 9 glow plug circuit.

OBD code P0679 applies to diesel vehicles and it means that the glow plug in cylinder 9 has failed to produce the high level of heat required to perform a cold start in a diesel engine. All diesels devices to heat the cylinders enough to ignite the fuel when the engine is cold, and this code identifies the cylinder 9 glow plug circuit as the problem.

The glow plug control module applies power to the glow plugs. The module is generally incorporated in the engine management computer, although so vehicles will have it separately. Too long an activation will melt the glow plugs as they produce heat through heavy resistance and glow red hot while activated. This intense heat is quickly transferred to the cylinder head which allows the heat of combustion to maintain its heat for the fraction of a second it takes to ignite the incoming fuel for starting.

What causes this problem with the Cylinder 9 Glow Plug Circuit?

• Faulty glow plugs
• Faulty glow plug relays
• Faulty glow plug module
• Glow plug wiring that is frayed, broken, or shorted
• Glow plug connectors that are damaged or corroded

1. Glow Plug - Check for faults in the Cylinder 2 Glow Plug and replace if needed. Buy new glow plug now!
2. Glow Plug Connector - Faulty or damaged wiring connector to the cylinder 2 glow plug should be replace, if necessary. Buy new connector now!
3. Glow Plug Relay - Check for faulty glow plug relay in association to the cylinder 2 and replace it now! Buy new glow plug relay from us!
4. Starter Relay - Check for the starter relay problems that can also be faulty and should be replaced at first instance. Buy new starter relay now!
5. Engine Control Module - Faulty ECM leads to engine stalling or not starting, and check engine lights being on. Replace damaged ECM now!
6. Engine Wiring Connector - Engine wiring and connector at fault must be replaced if found faulty. Buy new engine wiring and connectors now!
7. Powertrain Control Module - P0679 error code can also flash due to rare problems with the PCM. Replace faulty PCM related components immediately.
8. Diagnostic Tool - Choose a high grade and accurate diagnostic tools to detect and correct the OBD code error. Find all types of professional tools from us.

It is essential to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P0679 here:

Common Symptoms

• Engine is hard to start or doesn’t start at all
• Decreased engine power and acceleration
• Engine misfires
• Smoke from exhaust
• Glow Plug Warning Light is on
• Check Engine Light illumination

Want to correct the Trouble Code P0679? Read these points mentioned below:

• Faulty glow plugs replacement
• Glow plug relays replacement
• Glow plug module replacement
• Repair or replace glow plug wiring that is frayed, broken, or shorted
• Repair or replace glow plug connectors that are damaged or corroded

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If you want to easily diagnose this fault code, then all you have to do is to follow the steps which are mentioned below:

• Diagnostic trouble codes should be diagnosed in the order that they appear in the powertrain control module (PCM).
• Use an OBD-II scanner to collect all trouble codes that have been stored by the powertrain control module (PCM) as well as freeze frame data. Inspect the glow plug wiring for frays, breaks, and shorted wiring. Inspect the flow plug connectors for damage and/or corrosion.
• Repair or replace glow plug wiring that is frayed, broken, or shorted. Repair or replace glow plug connectors that are damaged or corroded. Clear all diagnostic trouble codes from the powertrain control module (PCM) and complete a test drive to see if the P0679 diagnostic trouble code comes back.
• If the P0679 trouble code does come back, test the glow plug connector using a volt ohmmeter.
• If the voltage reading is not within the manufacturer’s predetermined range, the glow plug will need to be replaced.
• After replacing the glow plug, clear all diagnostic trouble codes from the powertrain control module (PCM) and complete a test drive to see if the P0679 diagnostic trouble code comes back.
• If the P0679 trouble code comes back, test the resistance level of the glow plug relay. Compare the resistance level reading with the manufacturer’s specifications. If the resistance level reading does not fall within the manufacturer’s specifications, the glow plug relay will need to be replaced.
• Clear all diagnostic trouble codes from the powertrain control module (PCM) and complete a test drive to see if the P0679 diagnostic trouble code comes back.
• If the P0679 trouble code comes back, test the glow plug module. Compare the results of the test of the glow plug module with the manufacturer’s specifications. If the results of the test do not coincide with the manufacturer’s specifications, the glow plug module will need to be replaced.
• Clear all diagnostic trouble codes from the powertrain control module (PCM) and complete a test drive to see if the P0679 diagnostic trouble code comes back.
• If the P0679 trouble code comes back, it is possible that the powertrain control module will need to be replaced. It is rare that for the powertrain control module (PCM) to malfunction, but it is possible.

Common Mistakes When Diagnosing the P0679 Code

• Failure to check the glow plug relay for proper operation
• Failure to inspect glow plug connector for damage or corrosion
• Failure to inspect glow plug wiring for frays, breaks or shorts