Transmission Fluid Pressure Switch
The Transmission Fluid Pressure (TFP) switch is actually 5 pressure switches combined into a single unit mounted on transmission valve body. The PCM supplies battery voltage on 3 separate wires to TFP switch. As switches are actuated in various combinations during transmission operation, PCM can detect what gear transmission is in.
Transmission Fluid Temperature Sensor
The Transmission Fluid Temperature (TFT) sensor is a thermistor (temperature sensitive resistor) and is part of the Transmission Fluid Pressure (TFP) manual valve position switch. The PCM supplies and monitors a 5-volt signal to TFT sensor. This monitored 5-volt signal is then modified by resistance of TFT sensor. When transmission fluid temperatures are low, TFT sensor resistance is high and PCM sees a high monitored voltage signal. When transmission fluid temperatures are high, TFT sensor resistance is low and PCM sees a low monitored voltage.
PCM uses TFT sensor input to control Torque Converter Clutch (TCC) application and shift quality. Sensor circuit problem should set a related DTC.