Faulty cylinder 6 pressure sensor; Short to voltage in the signal circuit between the sensor and PCM; Damaged or corroded connector at the sensor or PCM; Open ground circuit for the sensor; PCM internal fault (rare); Wiring harness damage from heat, chafing, or rodent damage

DTC codes / P03xx · Ignition system and misfire / P03CA

P03CACylinder 6 Pressure Sensor Circuit High

Q: What does code P03CA mean?

Cylinder 6 Pressure Sensor Circuit High. P03CA indicates that the powertrain control module (PCM) has detected an abnormally high voltage signal from the cylinder 6 pressure sensor circuit, which is used on engines with cylinder pressure sensors to monitor combustion. The PCM expects the sensor to produce a voltage within a specific range, and a high reading typically means the signal wire is shorted to voltage or the sensor has failed.

P03CA indicates that the powertrain control module (PCM) has detected an abnormally high voltage signal from the cylinder 6 pressure sensor circuit, which is used on engines with cylinder pressure sensors to monitor combustion. The PCM expects the sensor to produce a voltage within a specific range, and a high reading typically means the signal wire is shorted to voltage or the sensor has failed.

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 running or misfire under load if the fault affects fuel or ignition timing calculations
Reduced engine power or limp mode in some vehicles
Poor fuel economy or increased emissions
Intermittent hesitation or stumble during acceleration
Possible difficulty starting or stalling in severe cases

Common causes, most likely first

Faulty cylinder 6 pressure sensor
Short to voltage in the signal circuit between the sensor and PCM
Damaged or corroded connector at the sensor or PCM
Open ground circuit for the sensor
PCM internal fault (rare)
Wiring harness damage from heat, chafing, or rodent damage

How to diagnose and fix it

Scan all modules for stored codes and freeze-frame data to confirm P03CA is current
Visually inspect the cylinder 6 pressure sensor and its connector for damage, corrosion, or loose pins
Check the sensor signal circuit for a short to voltage using a digital multimeter (DMM) with the key on and sensor disconnected
Measure sensor resistance and compare to manufacturer specifications if available
Perform a wiggle test on the harness while monitoring sensor voltage to detect intermittent faults
If the circuit tests good, replace the cylinder 6 pressure sensor with a known-good unit
Clear codes and verify the repair with a test drive, ensuring the code does not return

Cylinder pressure sensor circuit pitfalls

A high voltage reading on a pressure sensor circuit 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 ground circuit; a poor ground can cause the sensor signal to float high and set this code.
Cylinder pressure sensors are used on advanced engines for precise combustion control, and a fault here may not cause noticeable drivability issues until the PCM defaults to a backup strategy.
Intermittent codes can be caused by a loose connector that only loses contact during engine vibration or temperature changes, so a wiggle test is essential.
The PCM itself rarely fails, but a shorted sensor can damage the internal driver, so always check for a short before installing a new PCM.

Can I keep driving with P03CA?

You can usually drive with this code, but avoid heavy acceleration or towing until it is repaired, as the engine may enter limp mode or run poorly. If the check engine light is flashing or you notice severe misfiring, stop driving and seek professional diagnosis immediately.

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.