Fault code P0712 is called “Transmission Fluid Temperature (TFT) Sensor “A” Circuit Low Input” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0712
This diagnostic trouble code (DTC) is a generic transmission code. Error P0712 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.
The transmission fluid temperature sensor (TFT) is part of the transmission fluid pressure valve (TFP). It is a thermistor that changes value depending on temperature.
As the temperature rises, the resistance decreases and as the temperature falls, the resistance increases. The PCM provides a 5V reference signal to the sensor and measures the voltage drop across the circuit.
When the transmission fluid is cold, the sensor resistance is high, and the PCM detects a high voltage signal. As the fluid temperature warms to normal operating temperature, the resistance decreases, and with it the signal voltage.
This sensor is used by the PCM or TCM to determine the fluid temperature of the automatic transmission. The signal is used to determine the best shift points and regulate line pressure.
In operation, this will cause the control module (PCM or TCM) to engage the torque converter clutch (TCC) earlier and disengage the overdrive gear. This is done to lower the fluid temperature if it becomes above normal.
This code is set if the sensor “A” circuit has a low signal that does not match the characteristics stored in the PCM / TCM memory.
Sometimes the problem can be related to internal mechanical problems inside the transmission. But more often, error P0712 is a problem with the electrical circuit of the TFPS sensor. This should not be overlooked, especially when dealing with an intermittent problem.
The troubleshooting steps can vary depending on the manufacturer, type of TFPS sensor, and wire colors.
Symptoms of vehicle malfunctions
The main signal that an error P0712 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the ECM memory as a malfunction).
- The vehicle starts in 2nd or 3rd gear (emergency mode).
- Unable to shift gears.
- Hard gear shifting or transmission slipping.
- Transmission overheating.
- Problems with engagement and disengagement of torque converter lockup clutch.
- Increased fuel consumption.
The severity of error P0712 is quite high, therefore it is recommended to eliminate the problem as soon as possible. Because ignoring the problem for a long time can lead to more extensive and costly repairs. Over time, the performance of the vehicle may decrease so much that it simply cannot be driven.
Factors that can cause this error code
The error code P0712 can mean that one or more of the following problems have occurred:
- Possible short to ground in the TFT sensor signal circuit.
- Probability of TFT sensor malfunction (internal short circuit).
- Contamination or low level of ATF transmission fluid.
- Transmission fluid passages are clogged or clogged.
- Mechanical failure inside the transmission.
- Sometimes the cause is a faulty PCM module.
How to fix or reset OBD-2 code P0712
Some suggested steps for troubleshooting and fix the error code P0712:
- Change ATF fluid and filter.
- Fill transmission fluid to required level.
- Flushing to clean inside channels of transmission.
- Testing, if necessary replacing faulty transmission fluid temperature sensor.
- Troubleshooting mechanical problems inside the transmission.
- Checking connectors as well as wiring.
- Flashing or replacing the PCM.
Diagnose and repair of problems
Always check the technical service bulletins (TSB) for your particular vehicle to get started. The problem may already be a known problem with a known fix issued by the manufacturer. This can save you time and money during diagnosis.
The next step is to locate the transmission fluid temperature (TFT) sensor. Once found, visually inspect the connector and wiring. Look for scratches, scuffs, exposed wires, burn spots, or melted plastic.
Disconnect the connector and carefully inspect the terminals inside the connector. Look to see if they look burnt or have a green tint indicating corrosion. If you need to clean the terminals, use an electrical contact cleaner and a plastic-bristle brush. Allow to dry and apply electrical grease to the contact areas of the terminals.
Using a diagnostic tool, clear the trouble codes from the memory and see if error P0712 returns. If the code returns, we will need to test the TFT sensor and associated circuits.
With the ignition key off, disconnect the electrical connector on the TFT sensor. Connect a digital voltmeter. The black wire to ground and the red wire to the signal terminal on the TFT sensor wiring harness connector.
Turn on the ignition key. Depending on the manufacturer’s specifications, the voltmeter should show either 12 volts or 5 volts. Jerk the connection and see if the reading changes. If the voltage is incorrect, replace the faulty wires or connector.
Check the sensor
Connect one ohmmeter wire to the signal terminal on the TFT sensor, and the other to ground. Check the resistance against the manufacturer’s specifications. Jiggle the connector on the transmission fluid temperature sensor, checking the resistance. If the ohmmeter reading differs from the manufacturer’s recommendation, replace the TFT sensor.
If the wiring and sensor tests are done, but you keep getting code P0712. You need to look at the PCM / TCM module as well as internal transmission failures. But you need to do this after replacing the TFT sensor. More often than not, it is the one that is the problem.
If you are unsure, get help from a qualified automotive diagnostician.
On which vehicles does this problem occur most frequently
Fault code P0712 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Dodge (RAM)
- Ford (Focus, Fusion)
- Hyundai (Solaris, ix55)
- Jeep (Grand Cherokee)
- Kia (Rio)
- Mitsubishi (Pajero)
- Nissan (Sentra)
- Subaru (Legacy)
- Toyota (Corolla, Sienna)
- Volkswagen (Polo)
Fault code P0712 can sometimes be found with other errors. The most common are the following: P0102, P0113, P0710, P0711, P0713, P0714, P0846, P0965.