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P1373 Ignition Coil - Cylinder 3 - Early Activation Fault

The OBD2 code P1373 indicates that the ignition coil for cylinder 3 is activating earlier than expected, which can lead to misfires or poor engine performance

Definition

The OBD2 code P1373 indicates that the ignition coil for cylinder 3 is activating earlier than expected, which can lead to misfires or poor engine performance

Common causes

  • Faulty ignition coil for cylinder 3
  • Wiring issues or damaged connectors
  • Faulty engine control module (ECM)
  • Incorrect spark plug gap or faulty spark plug
  • Vacuum leaks affecting cylinder performance
  • Engine misfire or poor combustion
  • Faulty crankshaft or camshaft position sensor
  • Electrical interference or shorts in the ignition system
  • Faulty ignition control module (if applicable)
  • Software issues in the ECM

Common misdiagnoses

  • Faulty ignition coil
  • Bad spark plug
  • Wiring issues or shorts
  • Engine control module (ECM) problems
  • Fuel injector issues
  • Vacuum leaks
  • Timing belt/chain problems
  • Compression issues in the cylinder
  • Faulty crankshaft or camshaft position sensors
  • Exhaust gas recirculation (EGR) 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. This can provide more context and help identify related issues

  2. 2. Inspect the Ignition Coil

    Visual Inspection: Check the ignition coil for any signs of damage, such as cracks, corrosion, or burnt areas

  3. 3. Connector Check

    Ensure that the electrical connector to the ignition coil is secure and free of corrosion or damage

  4. 4. Test the Ignition Coil

    Resistance Test: Use a multimeter to measure the resistance of the ignition coil. Compare the readings to the specifications provided in the vehicle's service manual

  5. 5. Swap Test

    If possible, swap the ignition coil with another cylinder (e.g., cylinder 1) to see if the fault code follows the coil. If it does, the coil is likely faulty

  6. 6. Inspect Wiring and Connectors

    Check the wiring harness and connectors leading to the ignition coil for any signs of wear, fraying, or short circuits. Repair or replace any damaged wiring

  7. 7. Check the Power and Ground Supply

    Verify that the ignition coil is receiving the correct voltage and ground signal. Use a multimeter to check for proper voltage at the coil connector while the engine is running

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

    If all other components check out, there may be an issue with the ECM. Ensure that the ECM is functioning properly and that it is sending the correct signals to the ignition coil

  9. 9. Inspect Spark Plugs

    Check the spark plug for cylinder 3 for wear or damage. Replace if necessary, as a faulty spark plug can cause ignition issues

  10. 10. Check for Vacuum Leaks

    Inspect for any vacuum leaks that could affect engine performance and lead to misfires, which may trigger the code

  11. 11. Perform a Compression Test

    Conduct a compression test on cylinder 3 to ensure that the cylinder is functioning properly. Low compression can lead to misfires and ignition faults

  12. 12. Clear Codes and Test Drive

    After performing repairs, clear the trouble codes and take the vehicle for a test drive to see if the code reappears.1

  13. 13. Consult a Professional

    If the issue persists after performing these steps, it may be best to consult a professional mechanic for further diagnosis. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P1373 code