P0712

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Automatic Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor. When the transmission fluid is cold, the sensor resistance is high. As the transmission fluid warms, the sensor resistance decreases. The TFT range is -40 to +150°C (-40 to +302°F).

The PCM provides a 5 volt reference through a fixed series resistor to the TFT circuit, and monitors the voltage after the resistor, as the voltage drop (signal) across the circuit.

When the PCM detects a voltage input of less than 0.20 V in the TFT Sensor circuit, indicating a short to ground or short together, then DTC P0712 sets. DTC P0712 is a type D DTC.

Conditions for Setting the DTC

^ System voltage is 10-16 volts.

^ The ignition is ON.

^ The PCM detects a TFT sensor voltage of 0.20 volts or less for 10 seconds.

Action Taken When the DTC Sets

^ The PCM does not illuminate the Malfunction Indicator Lamp (MIL).

^ The PCM calculates a transmission fluid default temperature as follows:

^ If any engine coolant temperature sensor codes are set, the PCM substitutes a transmission fluid temperature default value of 131°C (268°F).

^ If the engine coolant temperature is greater than 115°C (239°F), the PCM substitutes a transmission fluid temperature default value of 131°C (268°F).

^ If the engine run time is less than 3 minutes, the PCM substitutes the intake air temperature for the transmission fluid temperature value at start-up except if any inlet air temperature codes are set, the PCM sets default temperature to 0°C (32°F).

^ If engine run time is greater than 3 minutes and the engine coolant temperature is 45-115°C (113-239°F), the transmission fluid default temperature equals Engine Coolant Temperature (ECT)-10°C when the intake air temperature is less than 0°C (32°F) at start-up. If the intake air temperature is greater than 28°C (82°F) at start-up, the transmission fluid default temperature equals ECT +10°C. If the intake air temperature (IAT) is 0 - 28°C (32-82°F) or any IAT DTC codes are set then transmission fluid default temperature is set to coolant temperature.

^ If the engine run time is greater than 3 minutes and the engine coolant temperature is less than 45°C (113°F), the PCM substitutes a transmission fluid temperature default value of 12°C (54°F).

Conditions for Clearing the DTC

^ A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition 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 bent terminal.

- A backed out terminal.

- A damaged terminal.

- Poor terminal tension.

- A chafed wire.

- A broken wire inside the insulation.

- Moisture intrusion.

- Corrosion.

^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

^ Inspect the transmission harness for a short to ground. Inspect the engine harness for a short to ground.

^ Inspect the transmission cooling system for blockage or other restrictions.

^ Refer to Specifications / Electrical / Temperature vs Resistance.

^ Test the TFT Sensor at various temperature levels in order to evaluate the possibility of a skewed (mis-scaled) sensor.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

3. A scan tool display of 145°C (293°F) or more indicates that this DTC is current.

4. This action isolates the fault between the transmission harness and the engine harness.