WOMS
P code powertrain Medium severity

P1156 Fuel Select Switch Malfunction

The OBD2 code P1156 indicates a malfunction in the fuel select switch, which is responsible for selecting between different fuel sources in vehicles equipped with dual-fuel systems

Definition

The OBD2 code P1156 indicates a malfunction in the fuel select switch, which is responsible for selecting between different fuel sources in vehicles equipped with dual-fuel systems

Common causes

  • Faulty fuel select switch
  • Wiring issues or damaged connectors
  • Short circuit in the fuel select circuit
  • Faulty fuel pump relay
  • Malfunctioning fuel pump
  • ECM (Engine Control Module) issues
  • Corroded or loose electrical connections
  • Faulty fuel level sensor

Common misdiagnoses

  • Fuel pump issues
  • Fuel injector problems
  • Air intake system leaks
  • Mass air flow sensor malfunction
  • Engine control module (ECM) faults
  • Fuel pressure regulator failure
  • Wiring or connector issues in the fuel system
  • Oxygen sensor 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. Addressing all related codes can help pinpoint the issue

  2. 2. Inspect the Fuel Select Switch

  3. 3. Check the physical condition of the fuel select switch. Look for any signs of damage, corrosion, or loose connections

  4. 4. Ensure that the switch is functioning properly. You may need to test it with a multimeter to verify that it is sending the correct signals

  5. 5. Examine Wiring and Connectors

  6. 6. Inspect the wiring harness and connectors associated with the fuel select switch for any signs of damage, fraying, or corrosion

  7. 7. Ensure that all connections are secure and free from dirt or moisture

  8. 8. Check the Fuel System

  9. 9. Verify that the fuel system is functioning correctly. This includes checking the fuel pump, fuel injectors, and fuel lines for any issues

  10. 10. Ensure that the correct fuel type is being used, as using the wrong fuel can sometimes trigger this code

  11. 11. Test the Fuel Selector Relay

  12. 12. If your vehicle has a fuel selector relay, test it to ensure it is functioning properly. A faulty relay can prevent the fuel select switch from operating correctly

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

  14. 14. In some cases, the issue may lie within the ECM itself. Check for any software updates or recalls related to the ECM

  15. 15. If necessary, perform a reset of the ECM by disconnecting the battery for a few minutes and then reconnecting it

  16. 16. Clear the Codes and Test Drive

  17. 17. After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner

  18. 18. Take the vehicle for a test drive to see if the P1156 code reappears. Monitor the vehicle's performance and fuel selection functionality

  19. 19. Consult a Professional

  20. 20. If the code persists after performing these troubleshooting steps, it may be necessary to consult a professional mechanic or technician who has experience with your specific vehicle make and model. By following these steps, you should be able to identify and resolve the issue related to the P1156 code