What it means
The second transmission fluid temperature sensor reports an over-temperature condition. Transmission fluid is too hot in the area monitored by sensor B.
At a glance
- Usually lights the check-engine light
How it works
Transmission fluid temperature sensor B measures fluid temperature in the area monitored by the second temperature sensor. This code sets when sensor B reports an over-temperature condition, which may reflect genuinely hot fluid from restricted cooling, low fluid, or sustained heavy load such as towing.
Common causes
Most likely first.
- Restricted transmission fluid cooler
- Sustained heavy load such as trailer towing
- Low transmission fluid level
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 readings from sensors A and B, if available, to see when sensor B reached the over-temperature condition.
- Compare the readings after a cold soak; sensor B should be reasonably consistent with ambient temperature and other available temperature readings.
- Check transmission fluid level and condition using the vehicle manufacturer’s specified procedure.
- Inspect the transmission cooler and its lines for obstruction, damage, or restricted airflow.
- If the readings suggest overheating but operating conditions do not, test sensor B and its wiring against the manufacturer’s diagnostic procedure.
Common fixes
- Restore the transmission fluid level using the manufacturer’s specified procedure and fluid.
- Clear debris or repair damage restricting the transmission fluid cooler or its lines.
- Reduce sustained heavy load, including trailer towing, until the transmission temperature is controlled.
- Replace sensor B if its temperature reading is inaccurate and its circuit tests correctly.
Can I keep driving?
Avoid towing, steep climbs, and hard acceleration until the cause is checked. If the transmission slips, shudders, shifts harshly, or warns of overheating, stop safely and let it cool; continued operation with overheated or low fluid can damage the transmission.
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.