P0204 Injector Circuit Malfunction - Cylinder 4

Definition

Common causes

• Faulty fuel injector for cylinder 4
• Open or shorted wiring in the injector circuit
• Poor electrical connection or corroded terminals
• Faulty engine control module (ECM)
• Failed injector driver in the ECM
• Fuel delivery issues (e.g., low fuel pressure)
• Grounding issues in the injector circuit
• Injector harness damage or wear

Common misdiagnoses

• Faulty fuel injector
• Wiring issues or short circuits
• Engine control module (ECM) failure
• Fuel delivery problems
• Vacuum leaks
• Ignition system issues
• Cylinder compression problems
• Faulty spark plug or ignition coil
• Injector driver circuit issues
• Fuel pressure regulator 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. Codes related to other cylinders or engine performance can provide additional context

2. 2. Visual Inspection

   Inspect the wiring and connectors for the fuel injector on cylinder 4. Look for signs of damage, corrosion, or loose connections

3. 3. Check the injector harness for any fraying or breaks

4. 4. Test the Injector

   Resistance Test: Disconnect the injector connector and use a multimeter to measure the resistance of the injector. Compare the reading to the manufacturer’s specifications (typically around 12-16 ohms for most fuel injectors)

5. 5. Injector Functionality

   If the resistance is within spec, you can perform a "buzz test" using a scan tool or a multimeter to check if the injector is receiving a signal when the engine is cranked

6. 6. Check Power and Ground

   With the injector connector still disconnected, check for power at the injector connector while the ignition is on. You should see battery voltage (typically around 12V)

7. 7. Check the ground side of the injector circuit. Ensure that the ground is solid and that there is continuity to the engine ground

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

   If the injector tests good, the issue may lie with the ECM. Check for any signs of damage or corrosion in the ECM connectors

9. 9. If possible, use a scan tool to monitor the injector pulse width and ensure the ECM is sending a signal to the injector

10. 10. Swap Injectors (if applicable)

    If you have access to a known good injector, you can swap the injector from cylinder 4 with another cylinder (e.g., cylinder 1) to see if the code follows the injector. If the code changes to the new cylinder, the injector is likely faulty

11. 11. Check for Fuel Supply Issues

    Ensure that the fuel supply to the injector is adequate. Check the fuel pressure and make sure it meets the specifications for your vehicle

12. 12. Inspect for Vacuum Leaks

    Vacuum leaks can cause performance issues that may trigger injector codes. Inspect hoses and gaskets for leaks

13. 13. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the codes and take the vehicle for a test drive to see if the code returns

14. 14. Consult Repair Manual

    If the issue persists, consult the vehicle’s repair manual for specific diagnostic procedures related to the fuel injector circuit for your make and model.1

15. 15. Seek Professional Help

    If you are unable to resolve the issue after these steps, it may be best to consult a professional mechanic for further diagnosis. By following these steps, you should be able to identify the cause of the P0204 code and take appropriate action to fix the injector circuit malfunction for cylinder 4