P03CF: Cylinder 6 Pressure Variation High

What it means

Cylinder-to-cylinder pressure variation on cylinder 6 is above the calibrated maximum — combustion is unstable cycle-to-cycle, typical of partial misfire or injector seat erosion.

At a glance

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

How it works

The controller compares cylinder 6 pressure from one combustion cycle to the next to detect unstable combustion. This code sets when that variation is greater than the calibrated limit, which can occur with a misfire, inconsistent injector delivery, or low compression in cylinder 6.

Common causes

Most likely first.

1. Misfire or incomplete combustion in cylinder 6
2. Fuel injector fault
3. Ignition fault, where applicable
4. Low compression

Symptoms

• Check-engine light
• Rough or uneven idle
• Engine misfire or hesitation
• Reduced engine power

How to diagnose it

1. Save freeze-frame data and check cylinder-specific misfire counts and pressure variation to confirm that cylinder 6 is the unstable cylinder.
2. Inspect the cylinder 6 pressure-sensor connector and harness, and check for related injector or ignition codes.
3. Test cylinder 6 injector operation and delivery using the manufacturer's procedure.
4. Where the engine has ignition components for each cylinder, inspect and test cylinder 6's ignition parts.
5. Measure cylinder 6 compression and compare it with the manufacturer's specification if fuel and ignition checks do not explain the variation.

Common fixes

• Repair a loose or damaged cylinder 6 sensor, injector, or ignition connection.
• Replace or service a cylinder 6 injector that fails testing.
• Repair a confirmed cylinder 6 ignition fault where applicable.
• Address low compression in cylinder 6 after mechanical testing identifies its cause.

Can I keep driving?

Avoid hard acceleration if the engine hesitates or misfires, and arrange diagnosis promptly. Stop driving if misfiring becomes severe or the engine loses substantial power, since continued operation can damage the engine or emissions system.