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P code powertrain High severity

P0871 Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance

The OBD2 code P0871 indicates that the transmission fluid pressure sensor or switch "C" is reporting a range or performance issue, suggesting that the sensor is detecting fluid pressure levels outside of the expected...

Definition

The OBD2 code P0871 indicates that the transmission fluid pressure sensor or switch "C" is reporting a range or performance issue, suggesting that the sensor is detecting fluid pressure levels outside of the expected range, which may affect transmission operation

Common causes

  • Faulty transmission fluid pressure sensor
  • Wiring issues (shorts, opens, or corrosion)
  • Poor electrical connections
  • Low transmission fluid level
  • Contaminated transmission fluid
  • Faulty transmission control module (TCM)
  • Internal transmission problems (e.g., pump failure)

Common misdiagnoses

  • Faulty transmission control module (TCM)
  • Incorrectly diagnosed transmission failure
  • Faulty wiring or connectors
  • Misinterpreted fluid level or condition issues
  • Faulty transmission fluid pressure sensor
  • Issues with other transmission sensors or switches
  • Engine control module (ECM) problems
  • Misdiagnosed electrical issues unrelated to the transmission

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: Check the transmission fluid level. Low fluid can cause pressure issues

  3. 3. Fluid Condition

    Inspect the fluid for contamination, burning smell, or discoloration. If the fluid is dirty or burnt, consider a fluid change

  4. 4. Visual Inspection

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

  5. 5. Sensor Condition

    Check the physical condition of the transmission fluid pressure sensor. Look for signs of damage or leaks

  6. 6. Test the Transmission Fluid Pressure Sensor

    Resistance Check: Use a multimeter to check the resistance of the 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 for Ground Issues

    Ensure that the transmission fluid pressure sensor has a good ground connection. A poor ground can lead to erratic sensor readings

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

    Check for any software updates or known issues with the TCM. Sometimes, reprogramming or updating the TCM can resolve communication issues

  10. 10. Test Drive the Vehicle

    After performing the above checks, take the vehicle for a test drive to see if the code returns. Monitor the transmission performance for any irregularities

  11. 11. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the P0871 code for your specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes

  12. 12. Replace the Sensor (if necessary)

    If the sensor is found to be faulty after testing, replace it with a new one. Ensure that the replacement part is compatible with your vehicle

  13. 13. Clear the Codes and Test Again

    After making repairs or replacements, clear the trouble codes using the OBD-II scanner and take the vehicle for another test drive to see if the code reappears.1

  14. 14. Seek Professional Help

    If the issue persists after following these steps, it may be time to consult a professional mechanic or transmission specialist for further diagnosis. By following these troubleshooting steps, you can systematically identify and address the underlying issues related to the P0871 code