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P0849 Transmission Fluid Pressure Sensor/Switch "B" Circuit Intermittent

The OBD2 code P0849 indicates that there is an intermittent issue with the transmission fluid pressure sensor or switch "B," which may be causing inconsistent readings or performance in the transmission system

Definition

The OBD2 code P0849 indicates that there is an intermittent issue with the transmission fluid pressure sensor or switch "B," which may be causing inconsistent readings or performance in the transmission system

Common causes

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

Common misdiagnoses

  • Faulty transmission fluid pressure sensor
  • Wiring issues or short circuits in the sensor circuit
  • Faulty transmission control module (TCM)
  • Low transmission fluid level or quality
  • Faulty transmission solenoids
  • Internal transmission problems
  • Electrical connector issues
  • Faulty engine control module (ECM)

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple 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, 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 for Ground Issues

    Ensure that the sensor has a good ground connection. A poor ground can lead to intermittent issues

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

    Check for any signs of damage or corrosion in the TCM connectors. Ensure that the TCM is functioning properly and is receiving the correct signals

  10. 10. Test the Circuit

    Use a multimeter to test the continuity of the wiring between the sensor and the TCM. Look for any breaks or shorts in the wiring

  11. 11. Check for Intermittent Issues

    Since the code indicates an intermittent issue, monitor the vehicle under different conditions (e.g., temperature, load) to see if the problem reoccurs

  12. 12. Clear Codes and Test Drive

    After performing the checks and repairs, clear the codes and take the vehicle for a test drive to see if the code returns

  13. 13. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P0849 code for your specific vehicle make and model. Manufacturers may have known issues and recommended fixes.1

  14. 14. Professional Diagnosis

    If the issue persists after performing these steps, consider seeking help from a professional mechanic or transmission specialist who can perform more advanced diagnostics. By following these steps, you should be able to identify the cause of the P0849 code and take appropriate action to resolve the issue