P03CE: Cylinder 6 Pressure Variation Low

What it means

Cylinder-to-cylinder pressure variation on cylinder 6 is below the calibrated minimum — pressure stays unusually constant cycle-to-cycle, often a sign that the closed-loop combustion controller has lost authority or the sensor signal is filtered.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The controller compares the cylinder 6 pressure trace across repeated combustion cycles to check that the signal reflects changing engine operation. This code sets when the measured pressure variation is unusually low, which may point to a sensor signal or processing problem that masks real cycle-to-cycle changes.

Common causes

Most likely first.

1. Combustion pressure sensor signal fault
2. Pressure signal filtering or processing fault
3. Combustion-control system fault

Symptoms

• Check-engine light
• Rough or uneven engine running
• Reduced engine power

How to diagnose it

1. Save freeze-frame data and compare cylinder 6 pressure variation with the other cylinders at the same engine speed and load.
2. Review live pressure data while engine speed and load change to see whether cylinder 6's trace remains unusually flat.
3. Inspect the cylinder 6 pressure-sensor connector and harness for damage, poor contact, or an intermittent signal.
4. Check the sensor signal and its wiring against the manufacturer's specifications.
5. If the sensor circuit passes, investigate the pressure-signal filtering and combustion-control system using vehicle-specific diagnostics.

Common fixes

• Repair a damaged connection or harness affecting the cylinder 6 pressure signal.
• Restore a loose or corroded cylinder 6 sensor connection.
• Replace the cylinder 6 pressure sensor if its output fails testing.
• Repair a confirmed signal-processing or combustion-control fault.

Can I keep driving?

If the engine runs evenly and only the check-engine light is on, gentle driving to arrange diagnosis is generally reasonable. Reduce speed and load if power drops or running becomes uneven, because the controller may not be assessing cylinder 6 combustion reliably.