P0710 Code: Transmission Fluid Temperature Sensor A Circuit
The transmission computer lost a usable fluid temperature signal and is guessing the temperature instead.
At a glance
Severity: Low
- Meaning
- Transmission Fluid Temperature Sensor A Circuit
- System
- Transmission · Powertrain
- Safe to drive?
- Yes, short term
- Typical repair cost
- $80–$2,200
- DIY difficulty
- Hard
The transmission fluid temperature (TFT) sensor is a thermistor whose resistance falls as the fluid warms. The module uses its reading to soften shifts when the fluid is cold, to decide when the torque converter clutch may lock, and to protect the transmission when it runs hot. P0710 means the circuit as a whole is faulty – typically an open circuit that reads about -40 °F, or a reading that jumps around. On most vehicles the sensor is inside the transmission, clipped into the internal harness or valve body and sometimes built into the control module, so access usually means draining fluid and removing the pan.
Can I keep driving? Normally safe to drive in the short term. Expect firmer shifts and possibly no converter lockup, which costs some fuel economy; avoid towing and heavy loads because the transmission can no longer tell you it is overheating.
How to read P0710
- P Powertrain
- 0 Generic (SAE)
- 7 Transmission
- 10 Specific fault
Symptoms
- Firm or harsh shifts, especially once the car is warmed up
- Torque converter doesn't lock up – rpm higher than usual on the highway
- Late upshifts or no top gear as if the fluid were cold
- Transmission temperature reads -40 °F or jumps on the scan tool
- Slightly worse fuel economy
- Check engine light, frequently with P0700
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Open circuit or broken wire in the internal transmission harness
- Failed TFT sensor (thermistor open or erratic)
- Fluid wicking or corrosion at the case pass-through connector
- External harness damage between transmission and module
- Sensor integrated in the TCM or mechatronic unit failed
- Module software or input fault
Diagnosis step by step
Do a cold-soak comparison
After the car has sat overnight, key on and compare transmission fluid temperature with engine coolant and intake air temperature on the scan tool. All three should be within about 5–10 °F of each other; -40 °F or a wildly different value confirms a circuit or sensor fault.
Tools: OBD-II scanner
Check the case connector
Unplug the main transmission connector and inspect both halves. Fluid inside the plug means the connector seal or pass-through is leaking and can wick along the wires; clean both halves and replace the seal.
Tools: Flashlight, Screwdriver
Measure sensor resistance at the case
Using the pinout for your model, measure TFT resistance through the case connector. It should be several thousand ohms at room temperature and drop steadily to a few hundred ohms at operating temperature; an open reading means the sensor or internal harness is broken.
Tools: Multimeter
Test the circuit from the module side
With the sensor disconnected, the scan reading should show the coldest possible value; bridging the two TFT wires with a fused jumper should make it jump to the hottest value. If it does, wiring and module are fine and the fault is internal to the transmission.
Tools: Multimeter, OBD-II scanner
Replace sensor or internal harness
Drain the fluid, drop the pan and replace the sensor or the harness it's part of. Refill using the manufacturer's level procedure, which on many sealed units is done at a set fluid temperature – use an infrared thermometer on the pan if the new sensor isn't trusted yet.
Tools: Towels & shallow pan, Torque wrench
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean case connector and replace seal | Yes | $80–$200 |
| Replace TFT sensor (pan removal and fluid) | No | $200–$450 |
| Replace internal wiring harness or lead frame | No | $350–$800 |
| Replace TCM or mechatronic with integrated sensor | No | $900–$2,200 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Mercedes-Benz
On Mercedes five-speed automatics (722.6), a leaking connector adapter in the transmission case is a well-known problem: ATF seeps out and can wick up the harness toward the control module, causing temperature-sensor and solenoid circuit faults. The adapter seal and the harness condition should be checked first.
Emissions / smog test impact
Will fail
Because P0710 lights the check engine lamp, the car will fail an OBD-based emissions test in states that require one until the circuit is repaired and the code no longer returns.
Frequently asked questions
Why does a temperature sensor change how my car shifts?
Cold fluid is thick, so the computer changes shift pressure and timing to match. Without a reliable reading it uses a default value and a safe, firm shift strategy, and many units stop locking the torque converter altogether.
Can I still check my fluid level with P0710?
Be careful. Many dipstick-free transmissions are checked through a level plug with the fluid at a specific temperature read on the scan tool. With a faulty sensor that reading is useless, so measure pan temperature with an infrared thermometer or leave the check to a shop.
Where is the transmission fluid temperature sensor?
Usually inside the transmission, on the valve body or in the internal wiring harness; on some models it is part of the control module mounted on the transmission. Very few are external, which is why the job normally involves draining the fluid.
Is P0710 serious?
The sensor fault itself doesn't damage the transmission. The risk is that the computer can't protect against overheating, so heavy towing or long mountain climbs should wait until it is repaired.