What it means
The input/turbine shaft speed sensor B circuit signal is below the expected range.
At a glance
- Usually lights the check-engine light
How it works
Input/turbine shaft speed sensor B measures a transmission input or turbine shaft speed used by the control module for shift decisions. This code sets when sensor B's circuit signal falls below its expected low-side range.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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
- Read freeze-frame and live transmission data to compare sensor B speed with engine speed and note the conditions when it went low.
- Inspect sensor B's connector and wiring for chafing, exposed conductors, corrosion, or loose terminals that could pull the signal toward ground.
- Use the wiring diagram to test sensor B's signal wire for a short to ground and check its supply and ground connections.
- Check whether the sensor B reading changes plausibly as the shaft turns using supported scan data or the vehicle's service procedure.
- If the circuit is intact, test sensor B and the control module input against the manufacturer's specification.
Common fixes
- Secure or clean sensor B's connector if contact is poor.
- Repair chafed wiring or a signal wire shorted to ground.
- Repair a damaged supply or ground connection for sensor B.
- Replace input/turbine shaft speed sensor B if its output is faulty.
- Repair the transmission control module input circuit if sensor B and its wiring pass testing.
Can I keep driving?
Limit driving and avoid heavy loads if shifts are harsh, delayed, or slipping. If the transmission loses predictable shifting or locks into one gear, stop and arrange a tow because continued operation can cause damage.
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.