P0712
DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input
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 RED/BLK. 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) and CHECK TRAMS Lamp.
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 warm up 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 RED/BLK. 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" (mix-scaled) sensor.
A "skewed" sensor could result in delayed garage shifts or TCC complaints.
- Verify customer driving habits, trailer towing, etc.
Test Description
Resistance Chart
DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input
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.