WOMS
P code powertrain Medium severity

P0959 ASM Mode Circuit Intermittent

The OBD2 code P0959 indicates an intermittent issue with the Automatic Shift Mode (ASM) circuit, which affects the transmission's ability to operate in the specified shift mode

Definition

The OBD2 code P0959 indicates an intermittent issue with the Automatic Shift Mode (ASM) circuit, which affects the transmission's ability to operate in the specified shift mode

Common causes

  • Faulty transmission control module (TCM)
  • Wiring issues or damaged connectors
  • Poor electrical connections
  • Faulty sensors related to the ASM system
  • Software issues or programming errors
  • Low transmission fluid levels
  • Internal transmission problems
  • Corroded or shorted circuits

Common misdiagnoses

  • Transmission control module (TCM) failure
  • Faulty wiring or connectors
  • Incorrect transmission fluid level or type
  • Malfunctioning speed sensors
  • Engine control module (ECM) issues
  • Faulty transmission solenoids
  • Problems with the gear shift mechanism
  • Software issues or updates needed in the TCM or ECM

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes. Sometimes, multiple codes can provide more context for the issue

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to the transmission control module and the ASM (Automatic Shift Mode) circuit. Look for signs of damage, corrosion, or loose connections

  3. 3. Check the Transmission Fluid

    Ensure that the transmission fluid is at the correct level and in good condition. Low or dirty fluid can cause transmission issues

  4. 4. Test the ASM Circuit

    Use a multimeter to test the ASM circuit for continuity and proper voltage. Check for any shorts to ground or open circuits

  5. 5. Inspect the Transmission Control Module (TCM)

    If the wiring and connectors are in good condition, the issue may lie within the TCM itself. Check for any signs of damage or malfunction

  6. 6. Check for Software Updates

    Sometimes, manufacturers release software updates for the TCM. Check with the dealership or manufacturer to see if there are any updates available

  7. 7. Perform a Reset

    Clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns. This can sometimes resolve intermittent issues

  8. 8. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the P0959 code for your specific vehicle make and model. Manufacturers may have identified common issues and solutions

  9. 9. Professional Diagnosis

    If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who specializes in transmission issues

  10. 10. Consider Component Replacement

    If all else fails, you may need to consider replacing the TCM or other related components if they are found to be faulty.Conclusion Always refer to the vehicle's service manual for specific diagnostic procedures and specifications. If you're not comfortable performing these steps, it's advisable to seek help from a qualified technician