P0712

Circuit Description
The TFT sensor is a thermistor that controls the signal voltage to the PCM. The PCM supplies a 5-volt reference signal to the sensor on circuit GEN/RED. When the transmission fluid is cold, the sensor resistance is high. The PCM detects high signal voltage. As the transmission fluid temperature increases to the normal operating temperature of 100°C (212°F), the sensor resistance becomes less and the voltage decreases to 1.5 to 2 volts. With transmission fluid over temperature and DTC P0218 also set, check the transmission cooling system.
This DTC detects a continuous short to ground in the TFT signal circuit or the TFT sensor. This is a type "D" DTC.

Conditions For Setting The DTC
- Battery voltage is between 10 and 16 volts.
- Ignition is "on".
- TFT sensor indicating a voltage less than 0.4 volts.
- All conditions met for 20 seconds.

Action Taken When The DTC Sets
- Transmission default temperature will be:
80°C (176°F) if engine temperature code is set.
100°C (212°F) if engine temperature is warm.
80°C (176°F) if engine run time is greater than 5 minutes.
21°C (69.8°F) if engine run time is less than 5 minutes.
- The PCM will not illuminate the Malfunction Indicator Lamp (MIL).

Conditions For Clearing The DTC
- The DTC can be cleared from the PCM history by using a scan tool.
- The DTC will be cleared from history when the vehicle has achieved 40 warmup cycles without a failure reported.
- The PCM will cancel the DTC default actions when the fault no longer exists and the ignition is cycled "off" long enough to power down the PCM.

Diagnostic Aids
- Check harness routing for a potential short to ground in circuit GRN/RED. Scan tool TFT display should rise steadily to about 100°C (212°F), then stabilize.
- Inspect the wiring for poor electrical connection at the PCM and at the transmission 16-way connector. Look for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension as well. Also check for a chafed wire that could short to bare metal or other wiring. Inspect for a broken wire inside the insulation.
- When diagnosing for a possible intermittent short or open condition, move the wiring harness while observing test equipment for a change.
- The temperature to resistance value scale may be used to test the TFT sensor at the various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor.
A "skewed" sensor could result in delayed garage shifts or TCC complaints.
- Verify customer driving habits, trailer towing, etc.

Test Description
The numbers below refer to the step numbers on the diagnostic chart:
3. This test checks for a short to ground or a "skewed" sensor
4. This test checks for an internal fault within the transmission by creating an open.





Resistance chart








DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input