What it means
The third transmission fluid temperature sensor reading is implausible. 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 measures fluid temperature, and the control module checks whether its reading is plausible for operating conditions. P274B sets when sensor C's value falls outside the expected temperature behavior, which can indicate a drifting or aged sensor or incorrect seating in the fluid path.
Common causes
Most likely first.
- Sensor drift after thermal aging
- Sensor not seated properly in the fluid path
- Sensor element aged beyond calibration window
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 compare sensor C's temperature reading with other available transmission temperatures and the vehicle's recent operating conditions.
- Watch live sensor C data from a cold start through warm-up for a reading that changes implausibly or fails to track temperature.
- Inspect sensor C's connector and harness for chafing, moisture, corrosion, or terminals that move under light harness movement.
- Verify that sensor C is correctly seated in the fluid path and that its wiring is intact.
- Test sensor C's resistance or signal response across temperature changes using the manufacturer's specifications.
Common fixes
- Secure sensor C's connector and repair damaged wiring.
- Correct sensor C's seating in the fluid path.
- Replace sensor C if its temperature response is outside the manufacturer's specification.
- Repair a connector fault that causes the reading to change when the harness moves.
Can I keep driving?
Use gentle driving and avoid towing until sensor C's reading is verified, since implausible temperature data can disrupt shifts or trigger limp mode. Stop if slipping or shuddering worsens.
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.