What it means
The second 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 B sends its temperature signal to the transmission control module on a monitored circuit. This code sets when that signal falls below the circuit’s lower diagnostic threshold, commonly because sensor B is internally shorted, the signal wire is grounded, or connector contact is faulty.
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 B temperature to confirm whether the signal is unusually low or drops out while the fault is active.
- Inspect sensor B’s connector seals, terminals, and nearby harness for water entry, chafing, pushed-back pins, or corrosion.
- With live data visible, gently move the sensor B harness and connector to see whether the low reading changes.
- Use the manufacturer’s wiring diagram to check the sensor B signal for a short to ground and inspect its reference and ground circuits.
- If the wiring and connector pass, test sensor B for an internal short using the manufacturer’s procedure.
Common fixes
- Repair chafed sensor B signal wiring that is contacting ground.
- Clean or replace corroded terminals and restore damaged connector seals.
- Secure a pushed-back terminal or replace a connector that cannot maintain contact.
- Replace transmission fluid temperature sensor B if it is internally shorted.
Can I keep driving?
If shifting is normal, avoid towing and drive only as needed while the fault is diagnosed. Stop safely if the transmission shifts harshly, slips, or enters limp mode; a falsely low sensor B signal can lead to unsuitable shift control.
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.