What it means
The third transmission fluid temperature sensor signal is above the upper 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 reports fluid temperature through an electrical signal monitored by the control module. P274D sets when the signal rises above the circuit's upper diagnostic threshold, which can result from an open sensor element or a signal wire shorted to the 5-volt reference.
Common causes
Most likely first.
- Open sensor element
- Signal wire shorted to the 5 V reference
- 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 high compared with other available temperature readings.
- Inspect sensor C's connector for loose or corroded terminals and the harness for an open or damaged signal wire.
- Check for a signal wire short to the 5-volt reference using the wiring diagram and an appropriate circuit test.
- Test sensor C's signal, reference, and ground circuits against the manufacturer's specifications.
- If the wiring is intact, test sensor C for an open element.
Common fixes
- Repair a signal wire shorted to the 5-volt reference.
- Repair an open or damaged sensor C wire.
- Clean or repair corroded connector terminals.
- Replace sensor C if its element is open or otherwise outside the manufacturer's specification.
Can I keep driving?
Drive gently only as needed until the fault is checked; an falsely high temperature reading can affect shift control or trigger limp mode. Avoid towing and stop if slipping or severe shift problems occur.
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.