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P code powertrain High severity

P1587 Throttle Control Unit Modulated Command Malfunction

The OBD2 code P1587 indicates a malfunction in the throttle control unit's modulated command, suggesting that the engine control module (ECM) is not receiving the expected signal from the throttle control system

Definition

The OBD2 code P1587 indicates a malfunction in the throttle control unit's modulated command, suggesting that the engine control module (ECM) is not receiving the expected signal from the throttle control system

Common causes

  • Faulty throttle position sensor
  • Malfunctioning throttle actuator
  • Wiring issues or damaged connectors
  • Faulty engine control module (ECM)
  • Vacuum leaks
  • Dirty or faulty throttle body
  • Software issues or calibration problems
  • Electrical shorts or open circuits in the throttle control system

Common misdiagnoses

  • Throttle position sensor failure
  • Accelerator pedal position sensor issues
  • Wiring or connector problems
  • Electronic control module (ECM) failure
  • Idle air control valve malfunction
  • Vacuum leaks
  • Faulty throttle body
  • Software issues in the engine control unit (ECU)

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 Throttle Body

  3. 3. Check the throttle body for any signs of dirt, carbon buildup, or physical damage. Clean the throttle body if necessary using an appropriate cleaner

  4. 4. Ensure that the throttle plate moves freely and is not sticking

  5. 5. Examine Wiring and Connectors

  6. 6. Inspect the wiring and connectors related to the throttle control unit for any signs of damage, corrosion, or loose connections

  7. 7. Repair or replace any damaged wiring or connectors

  8. 8. Check Throttle Position Sensor (TPS)

  9. 9. Test the throttle position sensor for proper operation. Use a multimeter to check the voltage output and ensure it changes smoothly as the throttle is opened and closed

  10. 10. Replace the TPS if it is faulty

  11. 11. Inspect Accelerator Pedal Position Sensor

  12. 12. Similar to the TPS, check the accelerator pedal position sensor for proper function. Ensure it is sending the correct signals to the engine control module (ECM)

  13. 13. Verify ECM Functionality

  14. 14. Ensure that the engine control module is functioning correctly. If other components are working properly, the ECM may need to be tested or reprogrammed

  15. 15. Check for Vacuum Leaks

  16. 16. Inspect the intake system for any vacuum leaks that could affect throttle response. Use a smoke machine or spray soapy water to identify leaks

  17. 17. Perform a Throttle Relearn Procedure

  18. 18. After cleaning or replacing components, perform a throttle relearn procedure as specified by the vehicle manufacturer. This helps the ECM recalibrate the throttle control system

  19. 19. Test Drive the Vehicle

  20. 20. After completing the above steps, take the vehicle for a test drive to see if the code returns. Monitor the throttle response and engine performance

  21. 21. Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the throttle control system. If the issue persists after following these steps, it may be necessary to consult a professional mechanic or technician for further diagnosis and repair