P0712
DTC P0712 TFT Sensor Circuit Low Input (2.2L)Circuit Description
The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch. 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 Running the DTC
- The system voltage is 8-18 volts.
- The ignition switch is in the RUN position.
Conditions for Setting the DTC
The TFT sensor indicates a signal voltage less than 0.2 volts for 10 seconds.
Action Taken When the DTC Sets
- The PCM does not illuminate the malfunction indicator lamp (MIL).
Important: The actions listed below are in order of highest to lowest priority.
- The PCM determines a default TFT using the following matrix:
1. If any 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. If 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 IAT DTCs P0112 or P0113 are set or AT 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 IAT DTCs P0112 or P0113 are set and IAT is available and 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 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 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 ECT.
5. If the engine run time is greater than 300 seconds and any AT DTCs P0112 or P0113 are set or IAT is NOT available, then the default TFT is equal to the 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.
- The PCM stores DTC P0712 in PCM history.
Conditions for Clearing the DTC
- A scan tool clears the DTC from PCM history:
- The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission-related diagnostic fault occurring.
- The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch 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 backed out terminal
- A damaged terminal
- Reduced 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 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
Steps 1 - 3:
Steps 4 - 6:
Steps 7 - 10:
Steps 11 - 12:
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.