Transmission Fluid Pressure Manual Valve Position Switch

The Transmission Fluid Pressure (TFP) manual valve position switch consists of five pressure switches (two normally closed and three normally open) on the control valve body that sense whether fluid pressure is present in five different valve body passages. The combination of switches that are open and closed is used by the PCM to determine the actual manual valve position. The TFP manual valve position switch, however, cannot distinguish between Park and Neutral because the monitored valve body pressures are identical in both cases.

The switches are wired to provide three signal lines that are monitored by the PCM. These signals are used to help control line pressure, torque converter clutch apply and shift solenoid valve operation. Voltage at each of the signal lines is either zero or twelve volts.

In order to monitor the TFP manual valve position switch operation, the PCM compares the actual voltage combination of the switches to a TFP combination table stored in its memory.

The TFP manual valve position switch signal voltage can be measured from each pin-to-ground and compared to the combination table. On the transmission wiring harness assembly, pin "N" is signal "A", pin "R" is signal "B", and pin "P" is signal "C". With the AT wiring harness assembly connected and the engine running, a voltage measurement of these three lines will indicate a high reading (near 12 volts) when a circuit is open, and a low reading (zero volts) when the circuit is switched to ground.

The Transmission Fluid Temperature (TFT) sensor is part of the TFP manual valve position switch assembly.