P2C3B: Cylinder Head Temperature Sensor B Circuit High

What it means

The ECM detects a circuit high 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 on the cylinder head and signals the ECM. This code means the B circuit is reading higher than expected, so the ECM cannot use that temperature signal reliably.

Common causes

Most likely first.

1. Signal wire shorted to B+
2. Open sensor
3. Connector pins corroded - high contact resistance

Symptoms

• Check-engine light
• Engine temperature reading may be inaccurate
• Hard starting

How to diagnose it

1. Review freeze-frame data and compare sensor B's live reading with sensor A and the engine's cold-soak temperature to confirm whether B is implausibly high.
2. Inspect sensor B's connector and harness for an open circuit, damaged wiring, or a signal wire contacting battery voltage.
3. Check sensor B connector pins for corrosion or weak contact that could interrupt the signal.
4. Test the sensor B signal wire for an open or short to B+ using the manufacturer's circuit procedure.
5. Test sensor B against the manufacturer's specification and replace it if it is open or out of range.

Common fixes

• Clean corroded connector pins and secure the sensor B connection.
• Repair an open or shorted-to-B+ section of the sensor B signal wire.
• Replace cylinder head temperature sensor B if it fails the manufacturer's test.

Can I keep driving?

A misleading temperature reading can affect starting and conceal actual engine temperature. Drive only as needed while monitoring for overheating, and stop safely if the temperature rises or a warning appears.