Description of the P0677 fault code.
OBD2 Error Codes

P0677 Cylinder 7 Glow Plug Circuit Malfunction

26.05.2022 /

P0677 – OBD-II Trouble Code Technical Description

Trouble code P0677 is a general trouble code that indicates a fault in the cylinder 7 glow plug circuit.

What does the fault code mean P0677?

Trouble code P0677 indicates a fault in the cylinder 7 glow plug circuit. In diesel vehicles, glow plugs are used to heat the air in the cylinders when the engine is cold started. Each engine cylinder is usually equipped with a glow plug to heat the cylinder head. If the powertrain control module (PCM) detects abnormal voltage in the cylinder 7 glow plug circuit compared to the manufacturer's specified parameters, P0677 will occur.

Fault code P0677.

Possible reasons

Some possible reasons for the P0677 trouble code:

  • Damaged or broken wiring: Corrosion, damage or breaks in the electrical circuit leading to the cylinder 7 glow plug can cause this error to appear.
  • Glow plug problems: A damaged or faulty glow plug can cause the P0677 code. This may be caused by wear, corrosion, or other issues that prevent the spark plug from functioning properly.
  • Problems with the engine control module (ECM): Malfunctions in the engine control module can lead to P0677. For example, incorrect reading of sensor signals or incorrect control of glow plugs.
  • Relay or fuse problems: A faulty relay or fuses that control the glow plug circuit can also cause this error.
  • Problems with connections and connectors: Incorrect connection or damage to the connectors connecting the glow plug circuit can also cause P0677.

What are the symptoms of a fault code? P0677?

Some possible symptoms that may occur when the P0677 trouble code appears:

  • Difficulty starting the engine: If there is a glow-related problem with cylinder 7, the engine may be difficult to start or may not start at all.
  • Increased fuel consumption: Improper functioning of the glow plug may result in incomplete combustion of fuel, which may increase fuel consumption.
  • Power drop: Insufficient heating of cylinder 7 may result in reduced engine power.
  • Floating revolutions: Improper combustion in cylinder 7 may cause the engine speed to become unstable or fluctuate.
  • Exhaust smoke: If the fuel in cylinder 7 does not burn properly, black or white smoke may come out of the exhaust pipe.

These symptoms may occur to varying degrees depending on the specific cause of the P0677 code and the overall condition of the engine.

How to diagnose a fault code P0677?

To diagnose and resolve the problem associated with DTC P0677, you can follow these steps:

  1. Checking the glow plugs: Check the condition of the glow plugs for cylinder 7. Make sure they are not damaged or worn and are connected correctly.
  2. Electrical circuit check: Using a multimeter, check the electrical circuit, including the wiring and connectors, connecting the cylinder 7 glow plug to the engine control module (ECM). Make sure there are no breaks or corrosion and that all connections are properly grounded.
  3. Checking relays and fuses: Check the condition of the relays and fuses that control the cylinder 7 glow plug circuit. Make sure they are working and connected correctly.
  4. ECM diagnostics: If necessary, perform diagnostics on the Engine Control Module (ECM) to ensure that it is operating properly and is not malfunctioning.
  5. Using the Diagnostic Scanner: Using a vehicle diagnostic scan tool, read the P0677 code and perform additional tests to identify other related problems.
  6. Looking for Other Symptoms: Inspect other engine-related components and systems, such as the fuel injection and ignition system, to identify any additional problems that may be associated with the P0677 code.

After completing these steps, you will be able to better determine the cause of the P0677 code and take the necessary steps to resolve it. If you do not have the necessary equipment or experience to perform these steps, it is best to contact a qualified mechanic or auto repair shop for diagnosis and repair.

Diagnostic errors

When diagnosing DTC P0677, the following errors may occur:

  • Skipping glow plug check: If diagnostics are performed without checking the condition of the cylinder 7 glow plugs, the root cause of the problem may be missed. It is imperative to check the condition of the glow plugs first.
  • Unaccounted for electrical problems: Some errors may occur due to insufficient inspection of the electrical circuit, including wiring, connectors, relays and fuses. It is necessary to carefully check all connections and elements of the electrical circuit.
  • Problems with diagnostic equipment: Incorrect use or incorrect interpretation of data from a diagnostic scanner can also lead to diagnostic errors.
  • Insufficient attention to ECM: Failure to consider a possible faulty Engine Control Module (ECM) may result in a serious problem related to the ECM software or hardware being missed.
  • Neglect of other potential causes: Sometimes a trouble code can be caused by other problems not directly related to the glow plugs, such as problems with the fuel system or fuel injection system. It is important not to neglect checking other systems and components.

To avoid mistakes when diagnosing the P0677 trouble code, it is important to follow diagnostic procedures, including a comprehensive approach to testing all possible causes and using the correct diagnostic equipment.

How serious is the fault code? P0677?

Trouble code P0677 indicates a problem with the cylinder 7 glow plug circuit. Depending on how quickly the problem is resolved, the severity of the fault may vary. A few reasons why a P0677 code may be considered serious:

  • Difficulty starting the engine: A malfunction in the glow plug circuit may cause difficulty starting the engine, especially in cold weather.
  • Increased fuel consumption: Improper functioning of the glow plug may result in incomplete combustion of fuel, which may increase fuel consumption.
  • Decreased productivity: If cylinder 7 is not running efficiently due to improper heating, it may result in loss of power and reduced engine performance.
  • Increased emissions of harmful substances: Improper combustion of fuel can increase emissions of harmful substances, which can lead to problems with environmental standards and the overall health of the environment.
  • Damage to other components: Continued use of a glow plug with a faulty electrical circuit may cause damage to other engine components.

Overall, a P0677 code should be taken seriously, especially if it causes the engine to start hard or reduce engine performance. The faster the problem is identified and corrected, the less likely there are serious consequences for engine performance and the overall safety of the vehicle.

What repair will help eliminate the code? P0677?

The following steps are recommended to resolve the P0677 code:

  1. Checking the glow plug of cylinder 7: First you need to check the condition of the glow plug. If the spark plug is damaged or worn out, it should be replaced with a new one.
  2. Electrical circuit check: Check the electrical circuit connecting the glow plug to the engine control module (ECM). Make sure the wires are intact, there are no breaks or corrosion, and that all connections are secure.
  3. Checking the Engine Control Module (ECM): In some cases, the problem may be with the ECM itself. Check its operation using a diagnostic scan tool to ensure it is reading and controlling the glow plugs correctly.
  4. Replacing the glow plug heating sensor: If the problem persists after replacing the glow plug and checking the electrical circuit, the problem may be with the glow plug heat sensor. In this case, it is recommended to replace the sensor.
  5. ECM Software Update: Sometimes updating the ECM software can solve the problem, especially if the problem is related to the software or its settings.
  6. Checking for Other Possible Causes: If the above measures do not resolve the problem, additional diagnostic tests should be performed to rule out other possible causes, such as problems with the fuel system or fuel injection system.

If you are unsure of your skills or experience, it is recommended that you contact a qualified mechanic or auto repair shop for diagnosis and repair.

How to Fix P0677 Engine Code in 3 Minutes [2 DIY Methods / Only $9.83]

P0677 – Brand-specific information

Trouble code P0677 indicates a problem with the glow plug circuit in cylinder 7. This problem can occur in various makes and models of cars, a list of several popular car brands with explanation:

Please refer to the service manual or authorized dealer of your specific vehicle brand for more detailed specifications and recommendations for troubleshooting this problem.

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