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P0674 Glow Plug Control Module Circuit Open

The OBD2 code P0674 indicates that there is an open circuit in the glow plug control module, which affects the operation of the glow plugs in a diesel engine, potentially leading to starting issues or poor engine...

Definition

The OBD2 code P0674 indicates that there is an open circuit in the glow plug control module, which affects the operation of the glow plugs in a diesel engine, potentially leading to starting issues or poor engine performance

Common causes

  • Faulty glow plug control module
  • Open or shorted wiring in the glow plug circuit
  • Bad glow plug(s)
  • Corroded or loose connectors
  • Blown fuse related to the glow plug system
  • Faulty engine control module (ECM)
  • Poor ground connection in the circuit

Common misdiagnoses

  • Faulty glow plugs
  • Bad glow plug relay
  • Wiring issues or shorts
  • Faulty engine control module (ECM)
  • Fuel system problems
  • Injector issues
  • Battery or charging system problems
  • Intake air temperature sensor malfunction
  • Coolant temperature sensor issues
  • Exhaust gas recirculation (EGR) system problems

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues

  2. 2. Inspect the Glow Plug Control Module

    Locate the glow plug control module and visually inspect it for any signs of damage, corrosion, or loose connections

  3. 3. Ensure that the module is securely mounted and that all connectors are clean and free of debris

  4. 4. Test the Glow Plugs

    Check the resistance of each glow plug using a multimeter. The resistance should typically be within the manufacturer's specified range. If any glow plug shows an open circuit (infinite resistance), it may need to be replaced

  5. 5. Check Wiring and Connectors

    Inspect the wiring harness and connectors leading to the glow plug control module and glow plugs for any signs of wear, fraying, or damage

  6. 6. Look for any broken or corroded connectors that could cause an open circuit

  7. 7. Test the Glow Plug Control Module

    If the wiring and glow plugs are in good condition, test the glow plug control module itself. This may involve checking the power and ground circuits to the module

  8. 8. Consult the vehicle’s service manual for specific testing procedures and specifications

  9. 9. Check Fuses

    Inspect any fuses related to the glow plug system. A blown fuse could interrupt the circuit and cause the P0674 code

  10. 10. Check for Short Circuits

    Use a multimeter to check for any short circuits in the wiring that could affect the glow plug control module operation

  11. 11. Clear Codes and Test Drive

    After performing repairs or replacements, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  12. 12. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with diesel engines and glow plug systems.Additional Tips: - Always refer to the vehicle’s service manual for specific diagnostic procedures and specifications. - Ensure that you are working in a safe environment and take necessary precautions when dealing with electrical components. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0674 code