WOMS
P code powertrain Medium severity

P1644 Fuel Pump Speed Control Circuit Malfunction

The OBD2 code P1644 indicates a malfunction in the fuel pump speed control circuit, which affects the operation of the fuel pump's ability to adjust its speed based on engine demands

Definition

The OBD2 code P1644 indicates a malfunction in the fuel pump speed control circuit, which affects the operation of the fuel pump's ability to adjust its speed based on engine demands

Common causes

  • Faulty fuel pump speed control module
  • Damaged wiring or connectors in the fuel pump circuit
  • Failed fuel pump
  • Short circuit or open circuit in the fuel pump speed control circuit
  • Malfunctioning engine control module (ECM)
  • Corroded or loose electrical connections
  • Faulty fuel pump relay

Common misdiagnoses

  • Fuel pump failure
  • Fuel filter blockage
  • Faulty fuel pressure regulator
  • Wiring issues or shorts in the fuel pump circuit
  • Engine control module (ECM) failure
  • Ignition system problems
  • Air intake issues
  • Throttle position sensor malfunction

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 Fuel Pump Relay

    Check the fuel pump relay for proper operation. A faulty relay can prevent the fuel pump from receiving the correct voltage

  3. 3. Examine Wiring and Connectors

    Inspect the wiring and connectors associated with the fuel pump and its control circuit. Look for signs of damage, corrosion, or loose connections that could affect the circuit

  4. 4. Test the Fuel Pump

    Perform a fuel pump operation test to ensure that the pump is functioning correctly. You can do this by listening for the pump's operation when the ignition is turned on or by using a fuel pressure gauge to check the pressure

  5. 5. Check the Fuel Pump Control Module

    If your vehicle is equipped with a fuel pump control module, check its operation. This may involve testing the module for proper voltage and ground signals

  6. 6. Inspect the Fuel Pump Speed Control Circuit

    Use a multimeter to check the voltage and resistance in the fuel pump speed control circuit. Compare your readings to the specifications in the vehicle's service manual

  7. 7. Check for Ground Issues

    Ensure that the fuel pump and its control circuit have a good ground connection. A poor ground can lead to erratic operation

  8. 8. Look for Fuel System Issues

    Inspect the fuel system for any blockages or restrictions that could affect fuel flow. This includes checking the fuel filter and fuel lines

  9. 9. Clear the Codes and Test Drive

    After performing the necessary repairs, clear the trouble codes and take the vehicle for a test drive to see if the code reappears

  10. 10. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with your specific vehicle make and model.Additional Tips: - Always refer to the vehicle's service manual for specific diagnostic procedures and specifications. - Ensure safety precautions are taken when working with fuel systems, as they can be hazardous. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P1644 code