P03CC: Cylinder 6 Pressure Too Low

What it means

Cylinder 6 measured peak combustion pressure is below the calibrated minimum — typically low compression, weak injection, or stuck-open exhaust valve.

At a glance

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

How it works

The engine controller uses the cylinder 6 pressure trace to judge how strongly that cylinder is producing combustion. This code sets when cylinder 6's measured peak pressure falls below the calibrated threshold, which can reflect weak combustion or a loss of compression.

Common causes

Most likely first.

1. Low compression in cylinder 6
2. Fuel injector delivering too little fuel
3. Leaking or stuck-open valve
4. Worn or damaged piston rings

Symptoms

• Check-engine light
• Rough running or misfire
• Reduced engine power
• Increased fuel consumption

How to diagnose it

1. Save freeze-frame data and compare cylinder 6 pressure and misfire information with the other cylinders under the conditions that set the code.
2. Inspect cylinder 6 for obvious intake, exhaust, or wiring issues and check for related fuel or misfire codes.
3. Check cylinder 6 injector operation and delivery using the manufacturer's procedure to identify under-fuelling.
4. Perform a compression or leak-down test on cylinder 6 and compare results with the manufacturer's specification.
5. If compression is low, investigate the cylinder 6 valves, piston rings, and related mechanical sealing surfaces.

Common fixes

• Repair a loose or damaged connection affecting cylinder 6 fuel delivery.
• Clean or replace a cylinder 6 injector that fails its delivery test.
• Repair a leaking or stuck valve in cylinder 6.
• Repair cylinder 6 piston-ring or other mechanical damage if testing confirms it.

Can I keep driving?

Rough running, misfire, or reduced power means the engine should be driven only as far as needed to reach a safe place for diagnosis. Continued driving can worsen engine damage and increase emissions.