P2C3ACylinder Head Temperature Sensor B Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2C3A reports that the signal of cylinder head temperature sensor B sits below the lowest voltage the module accepts. Because these sensors are NTC thermistors, a very low voltage would stand for an impossibly hot head, so the usual reasons are a signal wire shorted to ground, water inside the plug or a sensor with an internal short. No manufacturer publicly documents this code. Ford's monitor for its first sensor shows the method: under 0.244 V for 5 seconds, checked continuously, sets the low-input code (P017C, older P1290). The ECM then has to substitute a value, and some calibrations play it safe with full fan operation or a warning. Expect a false overheat message or reduced power. High input is P2C3B, plausibility P2C39.
- What you may notice
- Overheat warning or very high head temperature in live data on a cold engine
- Cooling fans running at full speed without reason
- Check engine light, possibly reduced engine power
- Likely causes
- LikelySignal wire of sensor B chafed through to ground
- PossibleMoisture or coolant in the sensor connector
- PossibleInternal short in the thermistor of sensor B
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.