P0712

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Automatic Transmission Fluid Temperature (TFT) Sensor is pant of the Automatic Transmission Fluid Pressure Manual Valve Position Switch (Transmission Fluid Pressure (TFP) Val. Position Sw.). 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.

When the PCM detects a continuous short to ground in the TFT signal circuit or in the TFT Sensor, then DTC P0712 sets. DTC P0712 is a type D DTC.

CONDITIONS FOR SETTING THE DTC

^ The system voltage is 8-16 volts.

^ The ignition switch is in the RUN position.

^ The TFT Sensor indicates a signal voltage less than 0.2 volts.

^ All conditions met for 10 seconds.

ACTION TAKEN WHEN THE DTC SETS

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

^ The PCM determines a default Transmission Fluid Temperature (TFT) using the following matrix:

IMPORTANT: The actions listed below are in order of highest to lowest priority.

1. If any Engine Coolant Temperature (ECT) DTCs P0117 or P0118 are set, then the default TFT is equal to 135°C (275°F).

2. If the ECT is 125°C (257°F) or more, then the default TFT is equal to 135°C (275°F).

3. It the Engine Run Time is less than 300 seconds and:

^ No Intake Air Temperature (IAT) DTCs P0112 or P0113 are set and IAT is available, then the default TFT is equal to IAT.

^ Any Intake Air Temperature (IAT) DTCs P0112 or P0113 are set or IAT is NOT available, then the default TFT is equal to 90°C (194°F).

4. If the Engine Run Time is greater than 300 seconds and No Intake Air Temperature (IAT) DTCs P0112 or P0113 are set and IAT is available and Engine Coolant Temperature (ECT) is between 40 and 125°C (104 and 257°F) and:

^ IAT at start-up is less than 15°C (59°F), then the default TFT is equal to the Engine Coolant Temperature (ECT) plus 5°C (8°F).

^ IAT at start-up is greater than 35°C (95°F), then the default TFT is equal to the Engine Coolant Temperature (ECT) plus 10°C (16°F).

^ IAT at start-up is between 15 and 35°C (59 and 95°F), then the default TFT is equal to the Engine Coolant Temperature (ECT).

5. If the Engine Run Time is greater than 300 seconds and any Intake Air Temperature (IAT) DTCs P0112 or P0113 are set or IAT is NOT available, then the default TFT is equal to the Engine Coolant Temperature (ECT).

6. If the Engine Run Time is greater than 300 seconds and ECT is less than 40°C (104°F) or more, then the default TFT is equal to 60°C (140°F).

^ The PCM freezes shift adapts from being updated.

^ DTC P0712 stores in PCM history.

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.

^ Use the Temperature vs Resistance table when testing the TFT Sensor at various temperature levels. Test the TFT Sensor in order to evaluate the possibility of a skewed (mis-scaled) sensor. A skewed sensor can result in delayed garage shifts or Torque Converter Clutch (TCC) complaints.

^ The scan tool displays the transmission fluid temperature in degrees. After the transmission is operating, the fluid temperature should rise steadily to a normal operating temperature, then stabilize.

^ Verify customer driving habits, trailer towing, etc. Trailer towing should occur in D3.

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.

4. This step creates an open in the TFT circuit in order to test for an internal fault.