P0712: Transmission Fluid Temp Sensor Circuit Low Input
What Does Code P0712 Mean?
The transmission Fluid Temperature (TFT) sensor is a varuable resistor, also called a thermistor which changes it's resistance value depending on the actual temperature of the transmission fluid. As the transmission temperature increases so does the fluid and the resistance of the sensor decreases, and conversely as the temp decreases, the sensor resistance ill increase. The Powertrain control module (PCM or ECM) provides a 5-volt reference signal to the sensor and then measures the voltage drop across the circuit. When the transmission fluid is cool the sensor resistance is high and the computer detects high signal voltage. As the fluid temperature increases up to it's normal operating temperature, the sensor resistance lowers and the sensor signal voltage will decrease.
How The Code Is Set
Transmission Control Module (TCM) or the powertrain module (depending on system) detects very low voltage from the transmmission fluid temperature sensor.
Code P0712 Symptoms
- Check Engine Light on
- Transmission shift problems
- Shifting problems that change with temperature
Common Causes of Code P0712
- A fualty TFT sensor
- Transmission Temperature sensor faulty wiring open or shorted
- Temperature sensor circuit faulty electrical connections
- A bad TCM or powertrain module
How to Diagnose P0712
As with any trouble code a scanner is an invaluable tool to help diagnosis. If you have one, look at the TFT sensor data when the transmission is cold then also when hot. You can use a laser thermometer pointed on the trans oil pan to compare values. If they are not close to each other, then you need to go a little further. Using a volt / ohm meter and resistance charts that show the relationship between temperatures and resistance. These charts are availble online or in your vehicle service manual. Disconnect the TFT and test the resistance across it. Now compare that to the temperature chart you have found to see if it is within the specified range. The temperature and resistance will not be exact but they will fairly close on a properly functioning TFT sensor. If the sensor is reading properly then move your fingers along the wiring harness while moving the harness around to check for an intermittant problem. If all this is good to this point then the problem may be in transmission contol module (TCM) or powertrain computer.
What Will Fix Code P0712?
After proper diagnosis and replacing the sensor or fixing wiring or replacement of the computer. The sensor is a little difficult to replace. Depending on the veicle make and model, it is located either in the pan on the valve body or in the side cover. Clear all of the stored computer codes after repairs are made and take your vehicle for a test drive to see if you fixed the problem.
⇦ Code P0711; Code P0716 ⇨
