What it means
The fourth 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 D measures fluid temperature at the transmission's fourth sensing point. The control module monitors the sensor's electrical signal, and this code sets when that signal falls below the circuit's lower diagnostic threshold, which can indicate a short to ground or a sensor fault.
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
- Check freeze-frame data and live sensor D data to confirm the low reading and note the conditions when the code set.
- Inspect sensor D's connector and harness for fluid or water ingress, corrosion, damaged insulation, pin damage, or a signal wire touching ground.
- With the code active, gently wiggle the sensor D harness while monitoring the signal to look for a change that reveals a poor connection.
- Check the sensor D signal circuit for a short to ground and inspect connector pin contact before replacing parts.
- Test sensor D and its wiring using the manufacturer's procedure and specification to distinguish an internally shorted sensor from a harness fault.
Common fixes
- Clean and securely reconnect sensor D's connector if contact is poor.
- Repair a signal wire shorted to ground or damaged insulation in the sensor D harness.
- Repair corroded or damaged connector terminals and seals.
- Replace sensor D if its signal remains below threshold with the circuit verified.
Can I keep driving?
If the transmission shifts normally, a short trip to a repair location may be possible, but avoid towing and demanding driving. Stop if it slips, shifts unpredictably, or enters limp mode, since the module may be acting on an incorrect fluid temperature.
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.