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Error Code P0710 is defined as Transmission Fluid Temperature Sensor A Circuit Malfunction. This is a generic but uncommon trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. This code appears in vehicles with transmission fluid temperature sensor, such as Acura, Ford, Honda, Infiniti, Nissan, Jaguar, Lexus, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.
The TFT (transmission fluid temperature sensor) gives off a signal that is then used by the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) to determine shift points, line pressure and TCC (torque converter clutch control). This sensor is often found in the transmission oil pan.
The TFT sensor gets its reference voltage (generally around 5V) from the PCM. It varies its internal resistance in relation to transmission fluid temperature to send a return voltage signal from the PCM. The TFT sensor is a type of NTC (negative temperature coefficient) thermistor. This means the sensor’s internal resistance is inversely proportional to the oil temperature. The TFT signal voltage goes down when the transmission fluid temperature goes up, and vice versa.
Other related transmission fluid temperature sensor “A” error codes include:
In some cases, this code indicates a transmission problem. Thus, it’s good to have it addressed as soon as possible. Some of the noticeable common symptoms include:
- Delayed or harsh shifting
- Improper operation of the torque converter clutch
- Vehicle in “limp mode” which purposely limits the vehicle’s performance
Common causes for this code include:
- Defective transmission temperature sensor
- Defective transmission temperature sensor wiring
- Dirty, leaking, or low transmission fluid
- Damaged transmission
- Defective PCM
How to Check
Start the diagnosis by checking the condition and level of the transmission fluid; it must be in accordance with the manufacturer’s recommendation. Then, check the transmission fluid level sensor and its corresponding wiring. Check for signs of damage or loose connections in the wiring. Any damages must be repaired. Clear the codes and see if it returns.
Then, check the problem with the TSB (technical service bulletin). If you can’t find anything, then move forward in your diagnosis.
The next steps are generalized procedure acceptable for most vehicles. To diagnose your problem more accurately, refer to your vehicle’s diagnostic flow chart.
Test the Circuit
Check the transmission temperature sensor data parameter using the scan tool. Disconnect the TFT sensor. The scan tool value must drop to a very low value. Then, connect a jumper wire across the terminals. If the scan tool now shows a high temperature, the connection is good, and PCM can recognize the input. For this case, the problem could be in the sensor and not a circuit or PCM.
Test the Sensor
Disconnect the TFT sensor connector, then, set the DVOM (digital volt ohmmeter) at ohms and use it to measure the resistance between the two sensor terminals. Start the engine and watch the meter value; as the engine warms up, the value must decrease smoothly (check the engine temperature gauge at the dash to ensure the engine reaches its right operating temperature). If the engine temperature increases, but the TFT resistance fails to increase, then that means the sensor is defective and must be replaced.
Test the circuit
With the ignition on, use the DVOM (set at volts) to check reference voltage (5V from the PCM) at the side of the circuit, check one or two transmission fluid temperature sensor terminals. If there’s no voltage present, turn off the ignition and connect the meter (this time set at ohms) between the reference voltage pin on the TFT and the reference voltage pin on PCM. If the meter shows OL (out of limits), then you have an open circuit between the sensor and the PCM. Locate this open circuit and repair as soon as possible. If the meter shows numeric value, on the other hand, then there’s continuity.
If everything is in good condition at this point, then check if there’s 5V coming off of PCM at the reference voltage terminal. If there’s no 5V reference from PCM, then the PCM is faulty.
Test the Ground Circuit Side
With the ignition off, set the meter at ohms and then connect it between the ground terminal of the TFT sensor and PCM’s ground terminal. If the meter shows an OL (out of limits) reading, then there’s an open circuit between the sensor and PCM, which must be located and fixed.
If the meter shows numeric value, then there’s continuity.
Next, attach one of the meter’s lead to the PCM ground terminal, and the other to the chassis ground check the PCM if it has a ground to check for good ground in the PCM. Again, if the meter shows OL, then there’s an open circuit between PCM and ground, which must be fixed.
If the circuits are good, but the error code is still there, then there may be a transmission problem This is especially true if the transmission fluid temperature codes are set along with other transmission codes.
How to Fix
Depending on the diagnosis, common repairs for this code include:
- Replacement of the TFT sensor
- Repair or replacement of faulty transmission temperature sensor wiring
- Flushing and changing transmission fluid
The severity of this code varies from moderate to serious. As said earlier, this code could indicate a transmission problem. Thus, it’s extremely important to address it as soon as possible.
As with most transmission error codes, make sure to check the fluid if it’s low or dirty.