P0712

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
The Automatic Transmission Fluid Temperature (TFT) Sensor is a thermistor that controls the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a 5 volt reference signal to the sensor on circuit 1227. When the transmission fluid is cold, the sensor resistance is high. The PCM detects high signal voltage. As the transmission fluid temperature (TFT) increases to the normal operating temperature, the sensor resistance becomes less, and the voltage decreases.
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 B DTC.

CONDITIONS FOR SETTING THE DTC
^ The ignition is ON.
^ The TFT Sensor indicates a voltage of less than 0.14 volts.
^ All conditions met for 15 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM uses a TFT default of 140°C (275°F). The scan tool does not display the default temperature.
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns oft the MIL after three consecutive ignition cycles without a failure reported.
^ 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 cycles OFF long enough to power down the PCM.

DIAGNOSTIC AIDS
^ With a transmission fluid over temperature DTC P021 8 also set, inspect the transmission cooling system.
^ Inspect the harness routing for a potential short to ground in circuit 1227. The scan tool TFT Sensor display should rise steadily, then stabilize.
^ Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following problems:
- A bent terminal.
- A backed out terminal.
- A damaged terminal.
- Poor terminal tension.
- A chafed wire.
- A broken wire inside the insulation.
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ Test the TFT Sensor at various temperatures in order to evaluate the possibility of a skewed (mis-scaled) sensor. Use the Temperature vs Resistance table. A skewed sensor may cause delayed garage shifts or TCC complaints. Specifications
^ Verify the customer driving habits, trailer towing, weight, or towing in Overdrive.
^ First diagnose and clear any engine DTCs that are present. Then inspect for any transmission DTCs that may have reset.

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.
7. The TFT Sensor is part of the Automatic Transmission Wiring Harness Assembly.