What it means
The ECM detects a circuit intermittent/erratic fault on the cylinder head temperature sensor b circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Cylinder head temperature sensor B reports temperature to the ECM through its own connector and wiring. This code sets when the B signal becomes unstable or erratic, often as a loose connection or noisy ground reference changes with vibration.
Common causes
Most likely first.
- Sensor connector not seated
- Noisy ground reference
- Connector with intermittent contact under vibration
Symptoms
- Check-engine light
- Engine temperature reading may be inaccurate
- Intermittent hard starting
How to diagnose it
- Check freeze-frame data and monitor sensor B live data from a cold start to see whether its reading jumps while sensor A remains stable.
- Inspect sensor B's connector for a latch that is not seated, corrosion, loose pins, or signs of vibration-related contact loss.
- Check the sensor B harness and ground reference for chafing, loose grounds, or movement that coincides with signal changes.
- With the engine safely running, perform a gentle harness movement check while watching sensor B data for dropouts.
- Test sensor B, its ground reference, and wiring continuity according to the manufacturer's procedure if the signal still fluctuates.
Common fixes
- Fully seat and secure the sensor B connector.
- Clean or repair loose or corroded sensor B connector terminals.
- Repair a noisy or poor ground reference or damaged harness section.
- Replace sensor B if its output remains erratic after the connection and wiring are sound.
Can I keep driving?
Intermittent readings can cause hard starting and may give an unreliable indication of engine temperature. Keep trips short and avoid heavy loads until the signal is stable; stop if overheating is suspected.
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.