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P0958 ASM Mode Circuit High

The OBD2 code P0958 indicates a high voltage condition in the Automatic Shift Mode (ASM) circuit, which may suggest a malfunction in the transmission control system or related components

Definition

The OBD2 code P0958 indicates a high voltage condition in the Automatic Shift Mode (ASM) circuit, which may suggest a malfunction in the transmission control system or related components

Common causes

  • Faulty ASM (Automatic Shift Management) module
  • Short circuit in the ASM mode circuit
  • Open circuit in the ASM mode circuit
  • Corroded or damaged wiring/connectors
  • Faulty transmission control module (TCM)
  • Malfunctioning sensors related to the ASM system
  • Software issues or programming errors in the TCM or ASM module

Common misdiagnoses

  • Transmission Control Module (TCM) failure
  • Faulty wiring or connectors
  • Incorrectly diagnosed transmission issues
  • Sensor malfunctions
  • Battery or charging system problems
  • Engine control module (ECM) issues
  • Software or firmware glitches
  • Mechanical transmission problems
  • Grounding issues
  • Other electrical faults in the vehicle's system

Troubleshooting steps

  1. 1. Check the Vehicle's Battery and Charging System

    Ensure the battery is fully charged and in good condition

  2. 2. Check the alternator output to ensure it is functioning properly

  3. 3. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to the ASM mode circuit for any signs of damage, corrosion, or loose connections

  4. 4. Pay special attention to the wiring harness that connects to the transmission control module (TCM) and the ASM components

  5. 5. Test the ASM Circuit

    Use a multimeter to measure the voltage in the ASM mode circuit. Compare the readings to the specifications in the vehicle’s service manual

  6. 6. Check for short circuits to ground or to power in the circuit

  7. 7. Check the Transmission Control Module (TCM)

    If the wiring and connectors are in good condition, the TCM may be faulty. Check for any software updates or recalls related to the TCM

  8. 8. If possible, perform a TCM reset or reprogramming

  9. 9. Inspect Related Components

    Check other components that may be related to the ASM mode, such as the transmission range sensor, shift solenoids, and any other sensors that may affect transmission operation

  10. 10. Ensure that the transmission fluid is at the correct level and in good condition

  11. 11. Scan for Additional Codes

    Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues

  12. 12. Perform a Visual Inspection of the Transmission

    Inspect the transmission for any signs of leaks or damage that could affect its operation

  13. 13. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the P0958 code for your specific vehicle make and model, as there may be known issues or fixes

  14. 14. Clear the Code and Test Drive

    After performing any repairs or adjustments, clear the code and take the vehicle for a test drive to see if the code returns

  15. 15. Seek Professional Help

    If the issue persists after following these steps, it may be necessary to consult a professional mechanic or technician who specializes in transmission issues. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0958 OBD-II code