P0843 - TRANSMISSION FLUID PRESSURE SENSOR / SWITCH "A" CIRCUIT HIGH

The TFP Sensor (Transmission Fluid Pressure) transforms the transmission pressure into an electrical signal which is then sent to the vehicle’s computer through the Controller Area Network (CAN). Once the PCM receives the signal provided by the TFP Sensor, it uses this information to calculate transmission pressure or determine when a shift will occur.

If the TFP Sensor input “A” is not within normal operating voltages, DTC P0843 OBD2 is set.

• Check Engine light illuminated.
• Transmission shifts hard or erratic.
• Transmission slipping.

The causes of setting the P0843 OBDII fault code are:

• There may be damage to the TPF Sensor wiring.
• There may be a shortage in the power supply to the Transmission Fluid Pressure Sensor.
• The TPF Sensor ground circuit may be shorted.
• The Transmission Fluid Pressure Sensor could be faulty.
• Defective PCM, which is very unlikely.

To resolve the errors that are related to the P0843 OBD2 diagnostic code you should do the following:

• To start with a good diagnosis, you must begin with the verification of the Technical Service Bulletins.
• After locating the TFP Sensor, inspect all its wires and electrical connectors to check their condition. Check for corroded, frayed, or burned wires. Make any necessary adjustments to these components.
• Connect one wire from a DVOM to the ground and the other wire to the TFP Sensor wiring harness. You should observe a voltage ranging from 5 to 12 V on the meter. If the voltage obtained is not as indicated, repair the power supply or the ground wire of the circuit.
• Check the resistance level of the Transmission Fluid Pressure Sensor. This value should be the same as indicated by the manufacturer. A resistance outside the allowable parameters requires the replacement of the TFP Sensor.