P03CD: Cylinder 6 Pressure Too High

What it means

Cylinder 6 measured peak combustion pressure is above the calibrated maximum — typically pre-ignition, knock, over-fuelling, or runaway combustion.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The cylinder 6 pressure sensor measures the pressure peak during combustion. This code sets when that peak exceeds the controller's calibrated limit, which can accompany knock, early combustion, or excessive fuel in cylinder 6.

Common causes

Most likely first.

1. Abnormally early combustion or engine knock
2. Excessive fuel delivery to cylinder 6
3. Incorrect ignition timing
4. Combustion-chamber deposits

Symptoms

• Check-engine light
• Engine knocking or pinging
• Rough running
• Reduced engine power

How to diagnose it

1. Save freeze-frame data and review cylinder 6 pressure, knock, and fueling data to see when the high-pressure event occurred.
2. If the engine is knocking or the vehicle is in reduced-power mode, avoid load and check for related knock or fueling codes before further running.
3. Inspect cylinder 6 injector wiring and connections for damage that could lead to excessive fuel delivery.
4. Test cylinder 6 injector operation and compare commanded with measured fueling using the manufacturer's procedure.
5. Check ignition or injection timing, as applicable, and inspect cylinder 6 for deposits or mechanical causes of abnormal combustion.

Common fixes

• Repair a wiring or control fault causing excessive cylinder 6 fuel delivery.
• Clean or replace a cylinder 6 injector that fails testing.
• Correct a confirmed ignition or injection timing fault.
• Remove combustion-chamber deposits if inspection confirms they are contributing to the high pressure.

Can I keep driving?

Do not continue driving under load if the engine knocks, runs roughly, or has reduced power; stop safely and arrange diagnosis. High cylinder 6 combustion pressure can damage the piston, valves, or other engine parts.