WOMS
P code powertrain High severity

P0870 Transmission Fluid Pressure Sensor/Switch "C" Circuit

The OBD2 code P0870 indicates a malfunction in the transmission fluid pressure sensor or switch "C" circuit, which may involve issues such as an electrical fault, sensor failure, or problems with the transmission...

Definition

The OBD2 code P0870 indicates a malfunction in the transmission fluid pressure sensor or switch "C" circuit, which may involve issues such as an electrical fault, sensor failure, or problems with the transmission control module's ability to read the pressure sensor's data

Common causes

  • Faulty transmission fluid pressure sensor
  • Wiring issues (shorts, opens, or corrosion)
  • Poor electrical connections
  • Transmission fluid leaks
  • Low transmission fluid level
  • Faulty transmission control module (TCM)
  • Internal transmission problems

Common misdiagnoses

  • Transmission fluid issues (low fluid, contamination)
  • Faulty transmission control module (TCM)
  • Wiring or connector problems
  • Faulty transmission pressure sensor
  • Transmission solenoid issues
  • Internal transmission problems
  • Engine control module (ECM) issues
  • Incorrectly diagnosed shift solenoid 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 Transmission Fluid

    Fluid Level: Ensure that the transmission fluid is at the correct level. Low fluid can cause pressure issues

  3. 3. Fluid Condition

    Check the condition of the fluid. If it is dirty, burnt, or has a strange odor, it may need to be changed

  4. 4. Visual Inspection

    Wiring and Connectors: Inspect the wiring and connectors related to the transmission fluid pressure sensor. Look for signs of damage, corrosion, or loose connections

  5. 5. Sensor Condition

    Check the physical condition of the transmission fluid pressure sensor. If it appears damaged or worn, it may need to be replaced

  6. 6. Test the Sensor

    Resistance Check: Use a multimeter to check the resistance of the transmission fluid pressure sensor. Compare the readings to the specifications in the vehicle’s service manual

  7. 7. Voltage Check

    With the ignition on (engine off), check the voltage at the sensor connector. Ensure it is within the expected range

  8. 8. Check the Circuit

    Continuity Test: Perform a continuity test on the wiring between the sensor and the engine control module (ECM) to ensure there are no breaks or shorts in the circuit

  9. 9. Ground Check

    Ensure that the sensor has a good ground connection

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

    If the sensor and wiring are in good condition, the issue may lie with the Transmission Control Module. Check for any software updates or known issues with the TCM

  11. 11. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner. Take the vehicle for a test drive to see if the code returns

  12. 12. Professional Diagnosis

    If the code persists after all checks and repairs, it may be necessary to consult a professional mechanic or technician who has access to advanced diagnostic tools and equipment.Additional Considerations

  13. 13. Service Manual

    Always refer to the vehicle’s service manual for specific diagnostic procedures and specifications

  14. 14. Safety Precautions

    When working on the vehicle, ensure that you take appropriate safety precautions, especially when dealing with the transmission system. By following these steps, you should be able to identify the cause of the P0870 code and take appropriate action to resolve the issue