What it means
The signal from crankshaft position sensor B is below the expected level. This indicates a low signal condition; the cause may be in the sensor or its circuit.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Crankshaft position sensor B sends a signal the controller uses to track crankshaft position and rotation. This code sets when that signal falls below the expected level, which can result from a short to ground, poor connections, or a damaged sensor circuit.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Hard starting or no start
- Engine stalling or rough running
- Power loss
How to diagnose it
- Check freeze-frame data and live engine-speed readings during cranking to see whether sensor B's low signal coincides with hard starting or a no-start.
- Inspect sensor B's wiring for chafing through the insulation and its connector for corrosion, moisture, or loose terminals.
- Check the sensor mounting and visible tone wheel for damage or debris that could weaken the signal.
- Use the wiring diagram to test sensor B's signal, ground, and supply as applicable, and check for a short to ground using the manufacturer's procedure.
- If the circuit is intact, test sensor B's output against the manufacturer's specification before considering a controller fault.
Common fixes
- Repair chafed sensor B wiring that is shorting to ground.
- Clean or repair corroded connector terminals and restore loose connections.
- Correct a sensor mounting or tone-wheel issue that is weakening the signal.
- Replace sensor B if its output remains below specification with a sound circuit.
Can I keep driving?
A low sensor B signal can cause hard starting, stalling, or loss of power. Avoid driving if the engine stalls or is difficult to restart, and have the fault addressed promptly if it affects engine operation.
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.