Faulty cylinder 5 pressure sensor internally shorted; Damaged or chafed sensor wiring shorted to voltage; Corroded or loose electrical connector at the sensor or PCM; PCM internal fault causing incorrect signal interpretation; Water intrusion or contamination in the sensor connector; Aftermarket or incorrect sensor installed previously

DTC codes / P03xx · Ignition system and misfire / P03C0

P03C0Cylinder 5 Pressure Sensor Circuit High

Q: What does code P03C0 mean?

Cylinder 5 Pressure Sensor Circuit High. P03C0 indicates that the powertrain control module has detected an abnormally high voltage signal from the cylinder 5 pressure sensor circuit, which is used to monitor combustion pressure for that specific cylinder. The computer expects the sensor signal to stay within a calibrated range, and a high reading means the circuit is either shorted to voltage, the sensor has failed, or the wiring is damaged.

P03C0 indicates that the powertrain control module has detected an abnormally high voltage signal from the cylinder 5 pressure sensor circuit, which is used to monitor combustion pressure for that specific cylinder. The computer expects the sensor signal to stay within a calibrated range, and a high reading means the circuit is either shorted to voltage, the sensor has failed, or the wiring is damaged.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Rough idle or misfire sensation, especially under load
Reduced engine power or limp mode in some vehicles
Poor fuel economy due to incorrect fuel delivery calculations
Intermittent hesitation or stumble during acceleration
Failed emissions test due to increased exhaust emissions

Common causes, most likely first

Faulty cylinder 5 pressure sensor internally shorted
Damaged or chafed sensor wiring shorted to voltage
Corroded or loose electrical connector at the sensor or PCM
PCM internal fault causing incorrect signal interpretation
Water intrusion or contamination in the sensor connector
Aftermarket or incorrect sensor installed previously

How to diagnose and fix it

Perform a visual inspection of the cylinder 5 pressure sensor and its wiring harness for obvious damage or corrosion
Use a scan tool to check live data for the cylinder 5 pressure sensor signal and compare with other cylinders
Disconnect the sensor and measure reference voltage and ground at the connector with a digital multimeter
Check for continuity and short to voltage on the signal wire between the sensor and PCM
Swap the cylinder 5 pressure sensor with a known-good sensor from another cylinder to see if the code moves
If wiring and sensor are good, test the PCM for proper operation and reprogram or replace if necessary
Clear codes and perform a road test to verify the repair

Cylinder pressure sensor circuit pitfalls

A high voltage code often results from a short to voltage in the signal wire, which can be caused by a pinched harness near hot exhaust components.
Some technicians replace the sensor without checking the connector, but corroded terminals can create high resistance that mimics a sensor failure.
The cylinder 5 pressure sensor is sometimes integrated into the glow plug or injector, so a high circuit code may actually indicate a fault in that combined component.
In rare cases, a failing PCM driver can hold the signal line high, so always verify the PCM is not the culprit before replacing parts.
This code can set intermittently due to vibration or thermal expansion, so wiggle-test the harness while monitoring live data.

Can I keep driving with P03C0?

Driving with P03C0 is generally safe for short distances, but avoid heavy acceleration or towing because the engine may misfire or enter limp mode. Prolonged driving with a misfire can damage the catalytic converter, so schedule diagnosis soon.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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