4L80-E / 4L85-E Automatic Transmission

DTC P0712





Circuit Description with 4L80-E / 4L85-E Automatic Transmission
The automatic transmission fluid temperature (TFT) sensor is part of the 4L80-E automatic transmission (AT) 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 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.

If the PCM detects a continuous short to ground in the TFT sensor or signal circuit, then DTC P0712 sets. DTC P0712 is a type C DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Voltage

Conditions for Running the DTC
^ No TFT DTC P0713.
^ The engine is running for greater than 7 seconds.
^ The system voltage is 8-18 volts.

Conditions for Setting the DTC
The TFT sensor indicates a voltage of less than 0.14 volts for 17 seconds.

Action Taken When the DTC Sets
^ The PCM does not illuminates the malfunction indicator lamp (MIL).
^ The PCM commands increased line pressure.
^ The PCM freezes shift adapts.
^ The PCM determines default transmission fluid temperature using the following conditions:
- If the engine run time is less than 60 seconds then default TFT equals 47°C (117°F).
- If ECT is less than 20°C (68°F), then default TFT equals IAT.
- If the ECT is 20-110°C (68-230°F) then default TFT equals ECT.
- If the ECT is greater than 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 records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
^ 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 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
DTC P0712 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine.

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 exists.
4. This step tests for an internal fault within the transmission by creating an open.