P0679 Glow Plug Circuit DTC, Cylinder No. 9

P0679 – OBD-II Trouble Code Technical Description

Glow plug chain for cylinder No. 9

What does the fault code mean P0679?

DTC P0679 is specific to diesel engines and indicates a problem with the #9 cylinder glow plugs. This code means that the glow plug is not providing enough heat to start a cold engine. It is important to note that this code can apply to different makes of cars.

Symptoms of P0679 include:

1. Difficulty starting a cold engine.
2. Low engine power in cold weather.
3. Possible fluctuations in engine speed during acceleration.
4. Check Engine light on the dashboard.

The following repairs may be required to correct this problem:

1. Replace the glow plug of cylinder No. 9 if it is faulty.
2. Checking and replacing wires and connectors in the glow plug circuit.
3. Check and, if necessary, replace the glow plug control module.
4. Checking the resistance of the wires and the glow plug relay bus.
5. Checking and replacing fusible links in wires.

Please consult your specific vehicle's service and repair manual and a professional to diagnose and repair this problem, as specific repair steps may vary depending on the make and model of vehicle.

Possible reasons

Causes of DTC P0679 may include the following:

1. Faulty glow plug for cylinder No. 9.
2. Open or shorted glow plug circuit.
3. Damaged glow plug wiring connector.
4. The glow plug control module is faulty.
5. Worn, broken or shorted glow plug wires.
6. Damaged or corroded glow plug connectors.

To accurately identify and eliminate this malfunction, it is recommended to carry out diagnostics and repairs under the supervision of specialists or using the service manual for your specific vehicle.

What are the symptoms of a fault code? P0679?

Knowing the symptoms of a problem is essential to successfully dealing with the problem. Here are the main symptoms associated with diagnostic code P0679:

1. Difficulty starting the engine or its inability to start.
2. Reduced engine power and poor acceleration.
3. Engine misfires.
4. Detection of smoke from the exhaust system.
5. The glow plug warning light comes on.
6. Check the engine indicator light.

Code P0679 indicates a problem in the glow plug system and may manifest itself through the symptoms listed above. If you notice one or more of these signs, it is important to carry out further diagnosis and repairs to restore your vehicle to normal operation.

How to diagnose a fault code P0679?

To fully diagnose and repair the P0679 code, follow these steps:

1. Use a digital volt-ohm meter (DVOM) to perform tests.
2. Carry out checks until the problem is confirmed.
3. You will also need a basic OBD code scanner to reset your computer and clear the code.
4. Check the glow plug for cylinder #9 by disconnecting the wire connector at the plug.
5. Use a DVOM to measure the resistance between the glow plug terminal and ground. The range is 0,5 to 2,0 ohms (check your vehicle's specifications in the factory manual).
6. If the resistance is outside the range, replace the glow plug.
7. Check the resistance of the glow plug wire to the glow plug relay bus.
8. Pay attention to the condition of the glow plug relay and wiring connectors.
9. Check the wires leading to the glow plug for wear, cracks or missing insulation.
10. If faults are found, repair or replace the wiring and/or glow plug.
11. Connect the wires.
12. Clear diagnostic trouble codes from the powertrain control module (PCM) and complete a test drive to see if the P0679 code appears again.
13. If the code returns, check the glow plug connector with a voltmeter.
14. If the voltage reading does not meet the manufacturer's specifications, replace the glow plug.
15. If code P0679 still occurs, check the resistance level of the glow plug relay and replace it if necessary.
16. After replacing the relay, again, clear DTCs from the PCM and take it for a test drive.
17. If the P0679 code appears again, check the glow plug module and replace it if necessary.
18. After replacing the module, clear the DTCs again and test drive.
19. If the P0679 code continues to occur, the powertrain control module (PCM) may need to be replaced.

Follow these steps in the given order to successfully diagnose and resolve the problem associated with the P0679 code.

Diagnostic errors

Common errors when diagnosing a P0679 code include:

1. Not checking the performance of the glow plug relay.
2. Failure to inspect the glow plug connector for damage or corrosion.
3. Failure to check the glow plug wiring for abrasions, breaks or short circuits.
4. Skipping steps in the diagnostic process may result in the cause of the P0679 code being incorrectly determined.

How serious is the fault code? P0679?

Trouble code P0679, which is related to glow plug problems in the cylinder, is quite serious for diesel engines. This code can cause difficulty starting the engine, reduced power, and other engine performance problems. If it is not corrected, it may lead to undesirable consequences for the operation of the vehicle. Therefore, it is recommended to carry out diagnostics and repairs immediately to prevent further damage and ensure normal engine operation.

What repair will help eliminate the code? P0679?

To resolve DTC P0679, the following steps are recommended:

1. Replacing faulty glow plugs.
2. Replacing the glow plug relay.
3. Replacing the glow plug module.
4. Repair or replace worn, broken or shorted glow plug wires.
5. Repair or replace glow plug connectors if they are damaged or corroded.

It should be remembered that regular glow plug replacement and systematic maintenance can reduce the risk of this fault code and ensure more reliable operation of the diesel engine.

What is P0679 Engine Code [Quick Guide]