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P code powertrain Medium severity

P0066 Air Assisted Injector Control Circuit or Circuit Low

The OBD2 code P0066 indicates a problem with the air-assisted injector control circuit, specifically that the circuit is either malfunctioning or has a low voltage condition

Definition

The OBD2 code P0066 indicates a problem with the air-assisted injector control circuit, specifically that the circuit is either malfunctioning or has a low voltage condition

Common causes

  • Faulty air-assisted injector
  • Wiring issues (shorts, opens, or corrosion)
  • Poor electrical connections
  • Failed engine control module (ECM)
  • Vacuum leaks
  • Faulty sensors (e.g., MAP or MAF sensors)
  • Issues with the fuel system (e.g., low fuel pressure)
  • Malfunctioning fuel injectors

Common misdiagnoses

  • Faulty Mass Air Flow (MAF) Sensor
  • Vacuum Leaks
  • Throttle Position Sensor (TPS) Issues
  • Engine Control Module (ECM) Malfunction
  • Fuel Injector Problems
  • Air Intake System Issues
  • Wiring or Connector Problems
  • Fuel Pressure Regulator Failure
  • Exhaust Gas Recirculation (EGR) System Issues
  • Ignition System 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 related codes can help pinpoint the issue

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors associated with the air-assisted injector system. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the wiring harness leading to the air-assisted injector and the control module

  4. 4. Test the Air-Assisted Injector

    If accessible, test the air-assisted injector for proper operation. This may involve checking the resistance of the injector coil with a multimeter

  5. 5. Compare the readings to the manufacturer’s specifications. If the resistance is out of range, the injector may be faulty and require replacement

  6. 6. Check the Control Circuit

    Use a multimeter to test the voltage and ground at the injector connector while the engine is running. Ensure that the control circuit is receiving the correct voltage and that the ground is solid

  7. 7. If there is no voltage or ground, trace the circuit back to the engine control module (ECM) to identify any breaks or shorts

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

    If the wiring and injector are functioning correctly, the issue may lie within the ECM. Check for any software updates or recalls related to the ECM

  9. 9. In some cases, reprogramming or replacing the ECM may be necessary

  10. 10. Check for Vacuum Leaks

    Inspect the intake system for any vacuum leaks that could affect the air-fuel mixture and the operation of the air-assisted injector

  11. 11. Use a smoke machine or spray a flammable aerosol around the intake manifold and vacuum hoses to identify leaks

  12. 12. Review Fuel System Components

    Ensure that the fuel system is functioning properly, including the fuel pump, fuel filter, and fuel pressure regulator. Low fuel pressure can affect injector performance

  13. 13. Clear Codes and Test Drive

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

  14. 14. Seek Professional Help

    If the issue persists after following these steps, consider seeking assistance from a qualified mechanic or automotive technician who has experience with your specific vehicle make and model. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0066 code