P0845 - TRANSMISSION FLUID PRESSURE SENSOR / SWITCH "B" CIRCUIT

The TFP Sensor (Transmission Fluid Pressure) is located on the side of the valve body, internally in the transmission. Its function is to turn transmission pressures into an electrical signl, which is transmitted to the PCM (Powertrain Control Module) or TCM (Transmission Control Module). The voltage signal provided by the TFP sensor is used by the PCM / TCM to calculate the pressure required for efficient transmission operation.

The setting of DTC code P0845 OBD2 indicates that the PCM or TCM detected that the TFP Sensor “B” circuit input is outside acceptable parameters with respect to the normal operating voltages, which are determined by the manufacturer.

• Check Engine light turns on.
• Transmission slipping.
• Engine efficiency is reduced.
• Vehicle goes into emergency mode.

The P0845 OBDII diagnostic code is set by:

• TFP Sensor signal circuit may be open.
• The TFP Sensor signal circuit may have a short to voltage or ground.
• The Transmission Fluid Pressure Sensor may be faulty.
• A faulty PCM or TCM, in very rare cases.

To troubleshoot the P0845 OBD2 fault code you must do the following:

• Consult the TSBs that are available for your vehicle model. The information contained in them will be useful in the diagnosis.
• Before proceeding with the diagnosis of the P0845 OBDII code, you must check that no other codes are set, especially those related to the TFP Sensor. If such codes are found, repair them.
• Perform a visual inspection of the wiring harness related to the TFP Sensor. Check that none of the wiring is burned, worn or corroded. Repair or replace as needed.
• With the key off, unplug the connector on the TFP Sensor. Then with a multimeter check for 5 or 12 volts in the power circuit. Compare the result with the data given by the manufacturer, and if you find an incorrect voltage, repair the power or ground wire.
• With an ohmmeter check the resistance of the TFP Sensor. If these readings are not within the parameters set by the manufacturer, replace the sensor.