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P1235 Fuel Pump Control Out Of Range

The OBD2 code P1235 indicates that the fuel pump control circuit is operating outside of its expected range, which may suggest issues with the fuel pump, wiring, or the engine control module (ECM)

Definition

The OBD2 code P1235 indicates that the fuel pump control circuit is operating outside of its expected range, which may suggest issues with the fuel pump, wiring, or the engine control module (ECM)

Common causes

  • Faulty fuel pump
  • Fuel pump relay failure
  • Wiring issues or damaged connectors
  • Faulty fuel pump control module
  • Low fuel pressure
  • Blocked fuel filter
  • Faulty engine control module (ECM)
  • Poor ground connection

Common misdiagnoses

  • Faulty fuel pump
  • Fuel pump relay issues
  • Wiring or connector problems
  • Fuel pressure regulator failure
  • Engine control module (ECM) malfunction
  • Fuel filter blockage
  • Ignition system issues
  • Sensor malfunctions (e.g., crankshaft or camshaft position sensors)

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 for the issue

  2. 2. Inspect the Fuel Pump Relay

  3. 3. Locate the fuel pump relay in the fuse box

  4. 4. Check for proper operation by swapping it with a similar relay (if available) or testing it with a multimeter

  5. 5. Examine the Fuel Pump Fuse

  6. 6. Check the fuse associated with the fuel pump circuit. Replace it if it is blown

  7. 7. Inspect Wiring and Connectors

  8. 8. Visually inspect the wiring and connectors related to the fuel pump and the fuel pump control circuit for any signs of damage, corrosion, or loose connections

  9. 9. Pay special attention to the wiring harness leading to the fuel pump

  10. 10. Test the Fuel Pump

  11. 11. Use a multimeter to check the voltage at the fuel pump connector while the ignition is in the "ON" position (but the engine is not running). You should see battery voltage

  12. 12. If there is no voltage, the issue may be upstream in the circuit (relay, fuse, or ECM)

  13. 13. Check Fuel Pressure

  14. 14. Use a fuel pressure gauge to check if the fuel pump is delivering the correct pressure. Refer to the vehicle's specifications for the correct pressure range

  15. 15. If the pressure is low, the fuel pump may be failing

  16. 16. Test the Fuel Pump Control Module (if applicable)

  17. 17. Some vehicles have a dedicated fuel pump control module. If your vehicle has one, test it according to the manufacturer's specifications

  18. 18. Inspect the ECM

  19. 19. If all other components check out, the issue may lie with the engine control module. Check for any signs of damage or corrosion

  20. 20. Reprogramming or replacing the ECM may be necessary if it is determined to be faulty

  21. 21. Clear Codes and Test Drive

  22. 22. After performing repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  23. 23. Consult Repair Manual

  24. 24. Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the fuel pump control circuit. If you are not comfortable performing these steps or if the issue persists after troubleshooting, it may be best to consult a professional mechanic for further diagnosis and repair