P2350: Cylinder 9 Pressure Variation High

What it means

Cylinder-to-cylinder pressure variation on cylinder 9 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 engine controller estimates combustion pressure in cylinder 9 and compares its variation from one firing cycle to the next with a calibrated limit. This code sets when cylinder 9’s pressure variation exceeds that limit, which can indicate unstable combustion or an intermittent fuel delivery problem.

Common causes

Most likely first.

1. Rough combustion - excessive cycle-to-cycle variation
2. Injector intermittent on cylinder 9

Symptoms

• Check-engine light
• Rough running or misfire
• Engine vibration
• Reduced engine power

How to diagnose it

1. Record freeze-frame data and check live misfire or cylinder-balance information to see when cylinder 9 becomes unstable.
2. Inspect cylinder 9’s injector connector and wiring for looseness, corrosion, or damage that could interrupt fuel delivery.
3. Compare cylinder 9’s contribution or pressure-related data with other cylinders under the same operating conditions.
4. Test cylinder 9’s injector operation and delivery using the vehicle maker’s procedure to identify intermittent fueling.
5. If fueling checks pass, assess cylinder 9’s mechanical condition and combustion stability using manufacturer-specified tests.

Common fixes

• Repair a loose, corroded, or damaged cylinder 9 injector connector or wiring.
• Repair or replace a cylinder 9 injector that fails testing.
• Address a confirmed mechanical or combustion fault affecting cylinder 9.

Can I keep driving?

Avoid heavy acceleration and prolonged driving if the engine is shaking or misfiring; continued misfire can damage the emissions system and reduce power. Stop if the vibration becomes severe or the engine runs abnormally.