What it means
The ECM detects a circuit 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 measures temperature at its location in the cylinder head and sends the reading to the ECM. This circuit code means the ECM detects an electrical fault in sensor B's circuit and cannot depend on its temperature signal.
Common causes
Most likely first.
- Sensor failed
- Wiring or connector fault
Symptoms
- Check-engine light
- Engine temperature reading may be inaccurate
- Hard starting
How to diagnose it
- Review freeze-frame data and compare sensor B's live temperature with other available engine temperature readings, especially before a cold start.
- Locate cylinder head temperature sensor B using the vehicle's service information and inspect its connector and harness for looseness, corrosion, heat damage, or broken wiring.
- Check sensor B's power or reference, ground, and signal circuits for opens and shorts against the manufacturer's wiring diagram.
- Test sensor B's resistance or signal response using the manufacturer's specified procedure and compare it with the measured temperature.
- Repair the wiring or replace the sensor if it fails testing, then verify plausible readings from a cold engine through warm-up.
Common fixes
- Reconnect or clean and secure the cylinder head temperature sensor B connector.
- Repair damaged or heat-affected wiring in the sensor B circuit.
- Replace sensor B if it fails the manufacturer's electrical or response test.
- Clear the code and verify sensor B reports a plausible temperature through warm-up.
Can I keep driving?
Because sensor B can give the ECM an unreliable temperature reading, watch the temperature gauge or warning closely and stop if overheating is indicated. Avoid long drives until the circuit is repaired, especially if starting or temperature readings are abnormal.
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.