P230C: Cylinder 3 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance

What it means

The ECU continuously trims individual cylinders to equalise air-fuel ratio across the bank using ion-current or per-cylinder lambda feedback. For cylinder 3 the per-cylinder fuel correction has hit its software-side maximum or minimum without restoring balance, indicating the underlying mechanical or fuelling deviation is too large to compensate.

At a glance

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

How it works

The engine computer uses cylinder-specific lambda or combustion feedback to balance cylinder output and mixture. P230C means its adjustment for cylinder 3 has reached its allowed limit without correcting the imbalance, pointing to a problem affecting that cylinder.

Common causes

Most likely first.

1. Fuel injector for cylinder 3 has drifted in flow rate
2. Local intake or vacuum leak at cylinder 3
3. Reduced compression on cylinder 3

Symptoms

• Check-engine light on, possibly flashing
• Rough idle or engine vibration
• Hesitation or uneven acceleration
• Reduced power

How to diagnose it

1. Save freeze-frame data and review cylinder-specific balance or correction data to confirm cylinder 3 is the outlier and note when the fault occurs.
2. Inspect cylinder 3's injector connector, wiring, intake runner, and nearby vacuum hoses for damage, looseness, or leaks.
3. Compare cylinder 3 injector operation or flow with the other cylinders using the vehicle's supported scan-tool or injector test procedure.
4. Check cylinder 3 for ignition-related misfire evidence and resolve any separate ignition fault before reassessing the balance code.
5. If fuel and ignition checks do not explain the imbalance, compare cylinder 3 compression and leak-down results with the manufacturer's specification.

Common fixes

• Repair a loose or damaged cylinder 3 injector connector or wiring.
• Repair a vacuum or intake leak at cylinder 3.
• Clean or replace the cylinder 3 injector if it fails the applicable flow or operation test.
• Repair a cylinder 3 mechanical fault if compression or leak-down results are outside specification.

Can I keep driving?

Avoid hard acceleration and extended driving while the engine runs rough. If the check-engine light flashes or the misfire is severe, stop driving when safe; continued misfire can damage the catalytic converter.