C 1500 Truck 2WD V8-6.5L DSL Turbo VIN F (1998)
Transmission Temperature Sensor/Switch: Description and Operation
4L80-E Automatic Transmission
AUTOMATIC TRANSMISSION FLUID TEMPERATURE SENSOR ASSEMBLY
The automatic transmission fluid temperature (TFT) sensor assembly is a thermistor which is mounted in the wiring harness assembly. Low
transmission temperature produces high resistance, while high temperature produces low resistance.
The VCM/PCM supplies a 5-volt signal to the TFT sensor assembly through an internal resistor. Then the VCM/PCM measures the voltage drop in
the circuit. Voltage is high when the transmission is cold and low when the transmission is hot. The VCM/PCM uses the TFT sensor assembly in order
to regulate torque converter clutch apply, as well as shift quality.
DTCs P0711, P0712 and P0713 indicate a fault in the TFT Sensor Assembly circuit. After the vehicle has been started, transmission temperature
should rise steadily and stabilize between 90° - 115°C, depending on load. All three DTCs causes the VCM/PCM to use a default value of 140°C, thus
reacting as if the transmission were hot in either case. When DTCs P0711, P0712 or P0713 are set, the VCM/PCM freezes the shift adapts from being
updated, and the MIL illuminates. Some driveability symptoms will be noticed, especially when cold.
