The P0840 trouble code indicates a malfunction in the transmission fluid pressure sensor or switch “A” circuit.
P0840 Transmission Fluid Pressure Sensor/Switch “A” Circuit
Code symptoms P0840.
1. Difficulty shifting gears.
2. Transmission slipping or erratic shifting.
3. Transmission overheating.
4. Illumination of the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) on the dashboard.
Causes of the code P0840.
1. Faulty transmission fluid pressure sensor or switch.
2. Damaged or corroded wiring or connectors in the sensor circuit.
3. Low transmission fluid level or dirty fluid.
4. Internal transmission issues.
5. Faulty transmission control module (TCM).
Code Solutions P0840.
1. Replace the transmission fluid pressure sensor or switch if it is found to be faulty.
2. Repair or replace any damaged wiring or connectors in the sensor circuit.
3. Ensure the transmission fluid level is at the correct level and the fluid is clean. If necessary, perform a transmission fluid flush and refill.
4. Address any internal transmission issues if detected.
5. Check and, if necessary, replace the transmission control module (TCM) if other issues are ruled out.