P0712

Circuit Description
The Automatic Transmission Fluid Temperature (TFT) sensor is part of the 4L80-E Automatic Transmission (A/T) wiring harness assembly. 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 Powertrain Control Module (PCM) supplies a 5-volt reference signal to the sensor on circuit 1227 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. The PCM uses this information to control shift quality and Torque Converter Clutch apply. DTC P0712 is a type D DTC.

Conditions for Running the DTC
The ignition is ON.

Conditions for Setting the DTC
^ The TFT sensor indicates a voltage less than 0.14 volts.
^ All conditions are met for 15 seconds.

Action Taken When the DTC Sets
^ The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM commands increased line pressure.
^ The PCM freezes shift adapts.
^ The PCM determines a TFT default Transmission Fluid Temperature (TFT) using the following matrix:
- If the engine run time is less than 60 seconds then default TFT equals the Intake Air Temperature (IAT), plus 5 degrees.
- If the Engine Coolant Temperature (ECT) is less than 85°C (185°F) then default TFT equals IAT plus 10 degrees.
- If the ECT is 85°-110° C (185°-230°F) then default TFT equals ECT plus 10 degrees.
- If the ECT is greater 110°C (230°F) then default TFT is set to 140°C (284°F) and transmission shift pattern is in Hot Mode
- If ECT and TFT DTCs are both set then default TFT is 140°C (284°F).
^ The PCM stores DTC P0712 in PCM history.

Conditions for Clearing the DTC
^ A scan tool clears the DTC from PCM history.
^ The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission-related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
^ Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ First diagnose and clear any engine DTCs or Applied Pedal Position (APP) sensor DTCs that are present. Then inspect for any transmission DTCs that may have reset.
^ DTC P0218 may set approximately 600 seconds after DTC P0712 has set. Follow the diagnostic table for DTC P0712 before proceeding to the diagnostic table for DTC P0218.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for a short to ground or a skewed sensor by verifying the fault still exists.
4. This step tests for an internal fault within the transmission by creating an open.
6. This step inspects circuit 1227 of the A/T wiring harness assembly for being shorted to ground.