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P1392 Glow Plug Circuit High Input (Bank #1)

The OBD2 code P1392 indicates that there is a high input signal detected in the glow plug circuit for bank #1, which may suggest a malfunction in the glow plug system or related wiring

Definition

The OBD2 code P1392 indicates that there is a high input signal detected in the glow plug circuit for bank #1, which may suggest a malfunction in the glow plug system or related wiring

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)
  • Corroded or damaged connectors
  • Incorrect glow plug type or specification

Common misdiagnoses

  • Faulty glow plugs
  • Bad glow plug relay
  • Wiring issues or shorts in the glow plug circuit
  • Faulty engine control module (ECM)
  • Incorrectly diagnosed fuel system issues
  • Misdiagnosed injector problems
  • Battery or charging system issues
  • Faulty temperature sensors

Troubleshooting steps

  1. 1. Check the Glow Plugs:

    Visual Inspection: Inspect the glow plugs for physical damage or corrosion

  2. 2. Resistance Test

    Use a multimeter to check the resistance of each glow plug. A typical reading is usually between 0.5 to 5 ohms. If a glow plug shows infinite resistance, it may be faulty and needs replacement

  3. 3. Inspect the Glow Plug Relay:

    Functionality Check: Test the glow plug relay to ensure it is functioning correctly. A faulty relay can cause high input signals

  4. 4. Power Supply

    Check for proper voltage at the relay terminals when the ignition is turned on

  5. 5. Check Wiring and Connectors:

    Visual Inspection: Look for damaged, frayed, or corroded wiring and connectors in the glow plug circuit

  6. 6. Continuity Test

    Use a multimeter to check for continuity in the wiring from the glow plugs to the relay and the engine control module (ECM)

  7. 7. Inspect the Engine Control Module (ECM):

    Software Updates: Ensure that the ECM has the latest software updates, as manufacturers may release updates to fix known issues

  8. 8. Faulty ECM

    If all other components check out, the ECM itself may be faulty and require testing or replacement

  9. 9. Check for Short Circuits:

    Short to Power: Inspect the circuit for any shorts to power that could cause a high input signal

  10. 10. Ground Issues

    Ensure that the ground connections for the glow plug circuit are secure and free of corrosion

  11. 11. Scan for Additional Codes:

    Check for Related Codes: Use an OBD-II scanner to check for any other related trouble codes that may provide additional context for the issue

  12. 12. Clear Codes and Test Drive:

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

  13. 13. Consult Repair Manual:

    If the issue persists, consult the vehicle's repair manual for specific diagnostic procedures and specifications related to the glow plug circuit

  14. 14. Seek Professional Help:

    If you are unable to diagnose or fix the issue, consider seeking help from a qualified mechanic or technician who has experience with diesel engines and glow plug systems. By following these steps, you should be able to identify and resolve the issue related to the P1392 code