What it means
The third transmission fluid temperature sensor signal is below the lower diagnostic threshold. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
Transmission fluid temperature sensor C sends a signal that the control module uses to estimate fluid temperature. P274C sets when that signal is below the circuit's lower diagnostic threshold, often because the sensor is internally shorted or the signal wire is shorted to ground.
Common causes
Most likely first.
- Internal short in sensor element
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and check whether sensor C's reported temperature is implausibly low compared with other transmission temperature readings.
- Inspect sensor C's connector and harness for corrosion, moisture, chafing, or a signal wire touching ground.
- Check whether moving the connector or harness changes the low reading.
- Test sensor C's signal circuit for a short to ground and inspect the connector terminals using the wiring diagram.
- If the wiring is sound, test sensor C against the manufacturer's specifications for a shorted element.
Common fixes
- Repair a signal wire shorted to ground.
- Clean or repair corroded sensor C connector terminals.
- Replace sensor C if its element is internally shorted.
- Repair chafed wiring and secure it away from grounded surfaces.
Can I keep driving?
Limit driving and avoid towing because the control module may misread fluid temperature and alter shifts or enter limp mode. Stop if the transmission slips, shudders, or shifts harshly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.