WOMS
P code powertrain Medium severity

P1604 Code Word Unregestered

The OBD2 code P1604 indicates that the Engine Control Module (ECM) has detected a problem with the communication or registration of the code word, which is typically related to the vehicle's immobilizer system

Definition

The OBD2 code P1604 indicates that the Engine Control Module (ECM) has detected a problem with the communication or registration of the code word, which is typically related to the vehicle's immobilizer system

Common causes

  • Faulty Engine Control Module (ECM)
  • Poor electrical connections
  • Damaged wiring
  • Software issues or bugs
  • Incorrectly programmed ECM
  • Faulty sensors or components related to the ECM
  • Battery voltage issues

Common misdiagnoses

  • Faulty Engine Control Module (ECM)
  • Wiring issues or short circuits
  • Faulty sensors (e.g., crankshaft or camshaft position sensors)
  • Battery or charging system problems
  • Poor ground connections
  • Incorrectly programmed or updated ECM
  • Faulty ignition system components
  • Fuel system issues

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 in diagnosing the issue more effectively

  2. 2. Inspect Battery and Connections

    Ensure that the vehicle's battery is in good condition and that all connections are clean and secure. A weak battery or poor connections can cause communication issues with the ECM

  3. 3. Reset the Code

    Clear the trouble code using an OBD-II scanner and see if it returns. If it does not return, it may have been a temporary glitch

  4. 4. Check Wiring and Connectors

    Inspect the wiring and connectors related to the ECM for any signs of damage, corrosion, or loose connections. Pay special attention to the wiring harness that connects to the ECM

  5. 5. Update ECM Software

    If the vehicle manufacturer has released any software updates for the ECM, consider updating it. Sometimes, software bugs can cause communication issues

  6. 6. Perform a Hard Reset

    Disconnect the battery for about 15 minutes to reset the ECM. Reconnect the battery and see if the code reappears

  7. 7. Check for Ground Issues

    Ensure that the ECM has a good ground connection. Poor grounding can lead to various electrical issues, including communication errors

  8. 8. Inspect the ECM

    If the above steps do not resolve the issue, the ECM itself may be faulty. Consider having it tested or replaced if necessary

  9. 9. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P1604 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues

  10. 10. Seek Professional Help

    If you are unable to resolve the issue after performing these steps, it may be best to consult a professional mechanic or technician who has experience with your vehicle's make and model. Always refer to the vehicle's service manual for specific diagnostic procedures and specifications related to your particular vehicle