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P code powertrain High severity

P1204 Injector Circuit Open / Shorted - Cylinder #4

The OBD2 code P1204 indicates a problem with the injector circuit for cylinder #4, specifically that the circuit is either open (disconnected) or shorted (electrically faulty), which can lead to improper fuel delivery...

Definition

The OBD2 code P1204 indicates a problem with the injector circuit for cylinder #4, specifically that the circuit is either open (disconnected) or shorted (electrically faulty), which can lead to improper fuel delivery to that cylinder

Common causes

  • Faulty fuel injector
  • Damaged wiring or connectors
  • Open circuit in the injector harness
  • Short circuit in the injector harness
  • Faulty engine control module (ECM)
  • Poor ground connection
  • Corroded or loose connectors

Common misdiagnoses

  • Faulty fuel injector
  • Wiring issues or damaged harness
  • Faulty engine control module (ECM)
  • Bad spark plug or ignition coil
  • Vacuum leaks
  • Fuel delivery problems
  • Compression issues in the cylinder
  • Faulty 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 additional context and help identify related issues

  2. 2. Visual Inspection

    Wiring and Connectors: Inspect the wiring and connectors leading to the injector for Cylinder #4. Look for signs of damage, corrosion, or loose connections

  3. 3. Injector Condition

    Check the injector itself for any physical damage or signs of wear

  4. 4. Test the Injector

    Resistance Test: Use a multimeter to measure the resistance of the injector. Compare the reading to the specifications provided in the vehicle’s service manual. A reading outside the specified range may indicate a faulty injector

  5. 5. Injector Functionality

    If possible, perform a bench test on the injector to ensure it is functioning properly

  6. 6. Check the Injector Circuit

    Power Supply: Verify that the injector is receiving the correct voltage. You can do this by checking the voltage at the injector connector while the ignition is on (but the engine is not running)

  7. 7. Ground Circuit

    Check the ground circuit for the injector. Ensure that the ground connection is solid and that there are no breaks in the wiring

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

    Connector Inspection: Check the connectors at the ECM for any signs of corrosion or damage

  9. 9. Signal Test

    If you have the capability, use a scan tool to monitor the injector pulse width and ensure the ECM is sending a signal to the injector

  10. 10. Check for Short Circuits

    Use a multimeter to check for continuity between the injector circuit and ground. A short circuit can cause the injector to malfunction

  11. 11. Test Related Components

    Fuses and Relays: Check the fuses and relays associated with the fuel injector circuit. Replace any that are blown or malfunctioning

  12. 12. Other Injectors

    If you have access to a known good injector, you can swap it with the one from Cylinder #4 to see if the problem follows the injector

  13. 13. Clear Codes and Test Drive

    After performing the above checks and making any necessary repairs, clear the trouble codes using the OBD-II scanner. Take the vehicle for a test drive to see if the code reappears

  14. 14. Seek Professional Help

    If you are unable to resolve the issue after these steps, it may be best 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 the cause of the P1204 code and take appropriate action to fix the issue