P0847 - TRANSMISSION FLUID PRESSURE SENSOR / SWITCH "B" CIRCUIT LOW

The Transmission Fluid Pressure Sensor (TFP) is responsible for measuring the transmission pressure and converting it into a voltage signal that is sent to the PCM (Powertrain Control Module). This signal is used by the vehicle’s computer to determine the transmission pressure when shifting occurs.

If input “B” of the TFP Sensor circuit is not within the levels allowed by the manufacturer, the diagnostic code P0847 OBDII is stored. This code, while partly indicative of electrical problems, can also be set for mechanical transmission failures. You should consult your vehicle’s data source for the particular “B” circuit.

• Check Engine lamp illumination.
• Transmission shifts hard.
• Transmission slips.
• The vehicle goes into emergency mode.
• Faulty electronic pressure control solenoid.
• Defective electronic pressure regulator.
• Mechanical problems within the internal transmission.
• Hydraulic blockages in the internal transmission fluid passages.
• Defective hydraulic pump.
• Malfunctioning PCM.
• Faulty Transmission Control Module.

The causes of the P0847 OBD2 trouble code are:

• The Transmission Fluid Pressure Sensor signal circuit may be shorted to the ground.
• Possibly the TFP Sensor has an internal short, resulting in a fault.
• PCM is defective, which is very unlikely.

The steps to troubleshoot faults related to the DTC P0847 OBDII code are:

• Review the Technical Service Bulletins that are available for your vehicle.
• After you have located your vehicle's Transmission Fluid Pressure Sensor, proceed to inspect its wires and connectors. Look for burnt, frayed wires or corroded connectors. Repair or replace it as needed.
• With the key in the off position and the TFP Sensor electrical connector unplugged, connect a voltmeter to a ground base and the signal terminal on the TPF Sensor harness connector. The voltmeter should show 5 or 12 volts. Manipulate the wires and observe if the voltage changes. If there is a voltage different from the manufacturer's specifications, repair the power or ground wires.
• Check with a DVOM that the resistance of the Transmission Fluid Pressure Sensor is as specified by the manufacturer. Replace the sensor if it does not meet the required values.
• If none of the above works, try replacing the electronic pressure control solenoid.
• If not, you can replace the electronic pressure regulator.
• Fluid pressure sensor replacement.
• Another option is to replace the hydraulic pump.
• In rare cases, it may be necessary to replace the PCM or transmission control module.