P0712
Diagnostic Chart:
Diagnostic Chart (cont'd):
Diagnostic Chart:
Wiring Diagram:
CIRCUIT DESCRIPTION
The Automatic Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within the Automatic Transmission Fluid Pressure (TFP) Manual Valve Position Switch. The TFT sensor controls the signal voltage from the 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, and the PCM detects high signal voltage. As the transmission fluid temperature increases, the sensor resistance decreases and the detected voltage decreases. At the transmission's normal TFT operating temperature, 100°C (212°F), the voltage is approximately 1.5-2 volts.
When the PCM detects a continuous short to ground in the TFT signal circuit or the TFT sensor, then DTC P0712 sets. DTC P0712 is a type B DTC.
CONDITIONS FOR SETTING THE DTC
- The system voltage is 1017 volts.
- The ignition is ON.
- The TFT sensor indicates a voltage less than 0.2 volts.
- All conditions met for 10 seconds.
ACTION TAKEN WHEN THE DTC SETS
- The transmission default temperature is 135°C (275°F).
- The PCM freezes shift adapts from being updated.
- The PCM illuminates the Malfunction Indicatory Lamp (MIL).
CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns OFF 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 is OFF long enough in order to power down the PCM.
DIAGNOSTIC AIDS
- If a transmission fluid overtemperature DTC P1812 is also set1 inspect the transmission cooling system for blockage and restrictions.
- Inspect the harness routing for a short to ground in circuit 1227. The scan tool TFT display should rise steadily to about 100°C (212°F), then stabilize.
- Inspect the wiring for poor electrical connections at the PCM. Look 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
- When diagnosing intermittent short or open condition, massage the wiring harness while watching test equipment for changes.
- Use the temperature versus resistance scale in order to test the TFT sensor at the various temperatures. Test the TFT sensor at the various temperatures in order to eliminate the possibility of a skewed (mis-scaled) sensor. A skewed sensor could result in delayed garage shifts or TCC complaints.
- Inquire about the customer's driving habits, trailer towing, etc.
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic chart.
3. Step 3 tests for a short to ground and a skewed sensor.
4. Step 4 creates an open. The Step uses the open in order to test for an internal fault within the transmission.
5. Step 5 verifies that the resistance of the TFT wiring and the TFT Sensor is within specifications at 20°C (68°F). In order to verify the resistance at other transmission fluid temperatures, you must refer to the 4L60-E TFT vs Resistance chart.