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P0671 Glow Plug Control Module Circuit Range/Performance Problem

The OBD2 code P0671 indicates a problem with the glow plug control module circuit, specifically that the performance or range of the circuit is outside the expected parameters, which can affect the operation of the glow...

Definition

The OBD2 code P0671 indicates a problem with the glow plug control module circuit, specifically that the performance or range of the circuit is outside the expected parameters, which can affect the operation of the glow plugs in a diesel engine

Common causes

  • Faulty glow plug control module
  • Bad glow plugs
  • Open or shorted wiring in the glow plug circuit
  • Poor connections or corroded terminals
  • Faulty engine control module (ECM)
  • Low battery voltage
  • Faulty relay or fuse related to the glow plug system
  • High resistance in the glow plug circuit

Common misdiagnoses

  • Faulty glow plugs
  • Bad glow plug relay
  • Wiring issues or shorts in the circuit
  • Faulty engine control module (ECM)
  • Incorrectly diagnosed fuel system issues
  • Misinterpreted sensor readings (e.g., temperature sensors)
  • Battery or charging system problems
  • Injector issues

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 Plugs

    Visual Inspection: Check the glow plugs for physical damage, corrosion, or carbon buildup

  3. 3. Resistance Test

    Use a multimeter to measure the resistance of each glow plug. Typically, a good glow plug will have a resistance of around 0.5 to 5 ohms. If any glow plug is out of this range, it may need to be replaced

  4. 4. Check the Glow Plug Control Module

    Visual Inspection: Inspect the glow plug control module for any signs of damage, corrosion, or loose connections

  5. 5. Power and Ground

    Verify that the control module is receiving the correct voltage and ground. Use a multimeter to check the power supply and ground connections

  6. 6. Inspect Wiring and Connectors

    Check the wiring harness and connectors associated with the glow plug circuit for any signs of damage, fraying, or corrosion. Repair or replace any damaged wiring or connectors

  7. 7. Test the Glow Plug Relay

    If your vehicle uses a relay to control the glow plugs, test the relay to ensure it is functioning properly. You can do this by swapping it with a known good relay or testing it with a multimeter

  8. 8. Check for Short Circuits or Open Circuits

    Use a multimeter to check for continuity in the glow plug circuit. Look for any short circuits or open circuits that could be causing the performance issue

  9. 9. Inspect Engine Coolant Temperature Sensor

    The engine coolant temperature sensor can affect the operation of the glow plugs. Ensure that it is functioning correctly and providing accurate readings to the engine control module (ECM)

  10. 10. Check the ECM

    If all other components are functioning correctly, the issue may lie with the engine control module itself. Check for software updates or reprogramming if necessary

  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 you are unable to diagnose or resolve the issue after these steps, it may be best to consult a professional mechanic or technician who has experience with diesel engines and OBD-II diagnostics. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0671 code