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P code powertrain High severity

P0843 Transmission Fluid Pressure Sensor/Switch "A" Circuit High

The OBD2 code P0843 indicates that the transmission fluid pressure sensor or switch "A" is reporting a high voltage signal, which may suggest a malfunction in the sensor, wiring, or the transmission control system

Definition

The OBD2 code P0843 indicates that the transmission fluid pressure sensor or switch "A" is reporting a high voltage signal, which may suggest a malfunction in the sensor, wiring, or the transmission control system

Common causes

  • Faulty transmission fluid pressure sensor
  • Wiring issues (short circuit or open circuit)
  • Poor electrical connections
  • Transmission fluid contamination
  • Faulty transmission control module (TCM)
  • Low transmission fluid level
  • Internal transmission problems

Common misdiagnoses

  • Faulty transmission fluid pressure sensor
  • Wiring issues or short circuits
  • Transmission control module (TCM) failure
  • Low transmission fluid level
  • Faulty transmission solenoids
  • Internal transmission problems
  • Engine control module (ECM) issues
  • Incorrect transmission fluid type or condition

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 incorrect pressure readings

  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 matches the expected voltage as per the service manual

  8. 8. Check for Short Circuits

    Inspect the wiring harness for any shorts to ground or power that could cause the circuit to read high. Use a multimeter to check for continuity and shorts

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

    If the sensor and wiring are in good condition, the issue may lie with the TCM. Check for any software updates or known issues with the TCM for your specific vehicle model

  10. 10. Perform a Transmission Fluid Pressure Test

    If possible, perform a pressure test on the transmission to ensure that the fluid pressure is within the manufacturer’s specifications. This may require specialized equipment

  11. 11. Clear Codes and Test Drive

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

  12. 12. Seek Professional Help

    If the issue persists after following these steps, it may be best to consult a professional mechanic or technician who has experience with transmission issues. By following these troubleshooting steps, you can systematically identify and address the cause of the P0843 code