Transmission Fluid Pressure Manual Valve Position Switch
Note. Seven valid combinations and two invalid combinations are available from the TFP manual valve position switch. See TFP MANUAL VALVE POSITION SWITCH LOGIC table for valid/invalid combinations for range signal circuits "A", "B" and "C".
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.
| Gear | Signal "A" | Signal "B" | Signal "C" |
|---|---|---|---|
| Park/Neutral | HI | LOW | HI |
| Reverse | LOW | LOW | HI |
| Drive 4 | HI | LOW | LOW |
| Drive 3 | HI | HI | LOW |
| Drive 2 | HI | HI | HI |
| Drive 1 | LOW | HI | HI |
| Illegal | LOW | HI | LOW |
| Illegal | LOW | LOW | LOW |
| (1) HI = ignition voltage; LOW = zero volts. | |||
| (1) | HI = ignition voltage; LOW = zero volts. |
TFP MANUAL VALVE POSITION SWITCH LOGIC (1)
Transmission Fluid Temperature Sensor
The Transmission Fluid Temperature (TFT) sensor is part of the Transmission Fluid Pressure (TFP) manual valve position switch. The TFT sensor is a resistor, or thermistor, which changes value based on temperature. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases and as the temperature decreases, the resistance increases.
The PCM supplies a 5-volt reference signal to the TFT sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the PCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases. (Схема №57)
The PCM uses the TFT sensor information to control shift quality and TCC application.