Engine

P03C0 — Cylinder 5 Pressure Sensor Circuit High

Severity: medium Drive with care, to a shop

What P03C0 means

The engine control module monitors the signal voltage of the cylinder 5 pressure sensor (a combustion pressure sensor). Only some engines use these sensors, and they help fine-tune fueling and ignition. P03C0 sets when the signal stays above the expected range, which usually points to a bad sensor or a wiring open or short rather than true cylinder pressure.

Symptoms

  • Check engine light on
  • Rough idle
  • Loss of power or hesitation
  • Higher fuel consumption
  • Possible misfire on cylinder 5

Possible causes

  1. Failed cylinder 5 pressure sensor
  2. Signal wire shorted to power
  3. Open circuit or poor connection in the harness or connector
  4. Corroded or water-damaged connector
  5. Faulty engine control module (unlikely)
  6. Combustion problem on cylinder 5, such as an injector (unlikely)

How to diagnose

  1. Scan all codes and freeze frame data, and look for other cylinder 5 or misfire codes
  2. Inspect the sensor connector and harness for chafing, oil, moisture and corrosion
  3. Check sensor supply voltage and ground against the factory wiring diagram
  4. Test the signal wire for a short to voltage or an open circuit
  5. Wiggle the harness with the engine running while watching scan tool data
  6. Swap in a known good sensor or compare readings with other cylinders
  7. Check compression, spark plug and injector on cylinder 5 if the signal looks plausible
  8. Consider the ECM only after ruling out the sensor and wiring

Common fixes

  • Replace the cylinder 5 pressure sensor
  • Repair the damaged harness and clean or replace the connector
  • Fix the signal wire short to power
  • Reflash or replace the ECM if confirmed faulty
  • Clear the code and road test

Questions and answers

What does P03C0 mean?

It means the signal from the cylinder 5 pressure sensor is too high. The sensor or its wiring is the most common culprit.

Can I drive with P03C0?

Briefly, if the engine runs smoothly. If it shakes, misfires or the check engine light flashes, do not drive and get it checked.

How do I fix P03C0?

Inspect the sensor connector and harness, measure the voltages, and replace the sensor if needed. Replace the control module last.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.