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P1394 Glow Plug Circuit High Input (Bank #2)

The OBD2 code P1394 indicates that there is a high input signal detected in the glow plug circuit for bank #2, which may suggest a malfunction in the glow plug or its circuit, potentially affecting engine starting and...

Definition

The OBD2 code P1394 indicates that there is a high input signal detected in the glow plug circuit for bank #2, which may suggest a malfunction in the glow plug or its circuit, potentially affecting engine starting and performance

Common causes

  • Faulty glow plug
  • Open or shorted wiring in the glow plug circuit
  • Bad glow plug relay
  • Poor electrical connections
  • Faulty engine control module (ECM)

Common misdiagnoses

  • Faulty glow plugs
  • Defective glow plug relay
  • Wiring issues or shorts in the glow plug circuit
  • Faulty engine control module (ECM)
  • Incorrectly installed or damaged glow plug harness
  • Fuel system issues
  • Injector problems
  • Air intake system leaks

Troubleshooting steps

  1. 1. Check the Code and Freeze Frame Data

    Use an OBD-II scanner to confirm the P1394 code and check for any additional codes that may provide more context

  2. 2. Review freeze frame data to understand the conditions under which the code was set

  3. 3. Inspect the Glow Plugs

    Visually inspect the glow plugs for any signs of damage, corrosion, or wear

  4. 4. Test the resistance of the glow plugs using a multimeter. A typical reading should be within the manufacturer's specifications (usually a few ohms). If any glow plug is open or has significantly higher resistance, it may need replacement

  5. 5. Check the Glow Plug Relay

    Inspect the glow plug relay for proper operation. A faulty relay can cause high input signals or prevent the glow plugs from receiving power

  6. 6. Test the relay by swapping it with a similar relay (if available) or using a multimeter to check for continuity

  7. 7. Inspect Wiring and Connectors

    Check the wiring harness and connectors leading to the glow plugs for any signs of damage, fraying, or corrosion

  8. 8. Ensure all connections are secure and free of dirt or moisture

  9. 9. Test the Glow Plug Control Module (if applicable)

    If your vehicle is equipped with a glow plug control module, test its operation. This module controls the timing and duration of the glow plug operation

  10. 10. Check for any fault codes related to the control module

  11. 11. Check for Short Circuits

    Inspect the wiring for any short circuits to ground or to other circuits that could cause a high input signal

  12. 12. Use a multimeter to check for continuity between the glow plug circuit and ground

  13. 13. Inspect the Engine Control Module (ECM)

    If all other components check out, the issue may lie with the ECM. Ensure that the ECM is functioning correctly and is not sending erroneous signals

  14. 14. Check for any software updates or recalls related to the ECM

  15. 15. Clear Codes and Test Drive

    After performing repairs or replacements, clear the trouble codes using the OBD-II scanner

  16. 16. Take the vehicle for a test drive to see if the code reappears

  17. 17. Seek Professional Help

    If the issue persists after performing these steps, consider seeking assistance from a qualified mechanic or technician who has experience with diesel engines and glow plug systems. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P1394 code