P235A: Cylinder 10 Pressure Variation High

What it means

Cylinder-to-cylinder pressure variation on cylinder 10 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 evaluates how much combustion pressure in cylinder 10 varies from one firing cycle to the next. This code sets when that variation exceeds the calibrated limit, pointing to unstable combustion such as an intermittent misfire or inconsistent injector delivery.

Common causes

Most likely first.

1. Unstable combustion in cylinder 10
2. Cylinder 10 injector delivery fault
3. Intermittent misfire

Symptoms

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

How to diagnose it

1. Save freeze-frame data and review live cylinder 10 misfire, contribution, or pressure-variation information to identify when the instability occurs.
2. Inspect cylinder 10’s injector connector and wiring for looseness, corrosion, chafing, or vibration-related damage.
3. Compare cylinder 10’s contribution or pressure behavior with other cylinders under the same operating conditions.
4. Test cylinder 10 injector operation and delivery using the manufacturer’s procedure, paying attention to intermittent behavior.
5. If injector checks pass, assess cylinder 10’s compression and combustion stability using manufacturer-specified tests.

Common fixes

• Repair a loose or damaged cylinder 10 injector connector or wiring.
• Repair or replace a cylinder 10 injector that fails testing.
• Address a confirmed compression or mechanical fault affecting cylinder 10.

Can I keep driving?

Avoid hard acceleration if the engine is vibrating or misfiring; prolonged unstable combustion can damage the emissions system and reduce power. Stop if the misfire becomes severe.