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DTC codes / P2Cxx · Hybrid propulsion / P2C3C

P2C3CCylinder Head Temperature Sensor B Circuit Intermittent/Erratic

P2C3C indicates that the powertrain control module (PCM) has detected an intermittent or erratic signal from the cylinder head temperature sensor B circuit. The PCM expects a stable voltage or resistance value from this sensor, but the signal is dropping out or fluctuating beyond acceptable limits, which can affect fuel delivery and engine protection strategies.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Intermittent rough idle or hesitation during warm-up
  • Poor fuel economy or rich-running condition
  • Fan running constantly or not engaging when needed
  • Temperature gauge fluctuating or reading incorrectly
  • Reduced engine power or limp mode in some vehicles

Common causes, most likely first

  1. Faulty cylinder head temperature sensor B
  2. Damaged or chafed wiring in the sensor circuit
  3. Corroded or loose electrical connector at the sensor
  4. Poor ground connection for the sensor circuit
  5. PCM software issue or internal fault (less common)
  6. Aftermarket accessories or modifications interfering with the circuit

How to diagnose and fix it

  1. Inspect the sensor connector and wiring for damage, corrosion, or loose pins
  2. Check the sensor resistance or voltage against the manufacturer's specification when cold and hot
  3. Perform a wiggle test on the harness while monitoring live data to identify intermittent opens
  4. Verify the sensor ground circuit has low resistance to the battery negative
  5. Repair or replace any damaged wiring or connectors as needed
  6. Replace the cylinder head temperature sensor B if it fails specification
  7. Clear the diagnostic trouble codes and verify the repair with a road test and live data monitoring

Intermittent sensor faults that fool technicians

  • A sensor that tests perfectly on a cold engine can still be faulty when heat-soaked, so always test both cold and at operating temperature.
  • The connector pins often spread or corrode internally, causing an intermittent signal that a visual inspection alone will not reveal.
  • Aftermarket alarm or remote start wiring tapped into the sensor circuit is a common cause of erratic readings that owners overlook.
  • The PCM may substitute a default temperature value when the signal is erratic, masking driveability symptoms and making the fault seem intermittent.
  • A weak battery or charging system can cause voltage fluctuations that mimic a sensor fault, so always check system voltage first.

Can I keep driving with P2C3C?

The vehicle is generally safe to drive short distances, but avoid heavy loads or sustained high-speed driving until the fault is repaired, as the PCM may not accurately protect the engine from overheating. If the temperature gauge behaves erratically or the engine enters limp mode, stop driving and seek professional diagnosis.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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