P0712

Circuit Description
The Automatic Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The PCM provides a 5 volt reference to the sensor on circuit 1227. A high fluid temperature or a short to ground on circuit 1227 results in low signal voltage. The TFT operating range is -40° to +151°C (-40° to +304°F).

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

Conditions for Setting the DTC

^ The system voltage is 10-16 volts.

^ The ignition is ON.

^ The PCM detects a TFT sensor voltage of 0.200 volts or less for 10 seconds.

Action Taken When the DTC Sets

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

^ The PCM disables shift adapts.

^ If the Engine Run Time is less than 3 minutes and:

- Intake Air Temperature (IAT) DTC P0112, P0113, P1111, or P1112 is set, then the default TFT is 0°C (32°F).

- No IAT DTC is set, then the default TFT is set to the IAT saved at start up.

^ If the engine run time is greater than 3 minutes, and the Engine Coolant Temperature (ECT) DTC P0117, P0118, P1114, or P1115 is set, then the default TFT is 131°C (268°F).

^ It the engine run time is greater than 3 minutes, no ECT DTC is set, and:

- The ECT is less than 45°C (113°F), then the default TFT is 12°C (54°F).

- The ECT is greater than 115°C (239°F), then the default TFT is 131°C (268°F).

- The ECT is 45-115°C (113-239°F) and:

^ The IAT DTC P0112, P0113, P1111, or P1112 is set, then the default TFT is set to equal the ECT.

^ The IAT at start up is less than 0°C (32°F), then the default TFT is set to ECT minus 10°C (18°F).

^ The IAT at start up is greater than 28°C (82°F), then the default TFT is set to ECT plus 10°C (18°F).

^ The IAT at start up is 0-28°C (32-82°F), then the default TFT is set to equal ECT.

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 for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Inspect the wiring for poor electrical connections at the Automatic Transmission Fluid Temperature sensor connector. Look for the following problems:

- A bent terminal

- A backed out terminal

- A damaged terminal

- Poor terminal tension

- A chafed wire

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

^ Test the TFT sensor at various temperature levels to evaluate the possibility of a skewed (mis-scaled) sensor. Refer to Temperature vs Resistance. Specifications

Test Description
The numbers below refer to the step numbers on the diagnostic chart.

3. This step verifies DTC P0712 by indicating a short to ground. If the scan tool does not display a voltage value equal to or less than 0.200 volts, then the DTC is intermittent.

4. This step isolates the transmission. If the scan tool displays a voltage greater than 4.920 volts, then the Engine Wiring Harness is good.