Faulty fuel injector on cylinder 4, such as a clogged nozzle or internal leak; Vacuum leak at the intake manifold runner or injector O-ring specific to cylinder 4; Worn or fouled spark plug on cylinder 4 causing incomplete combustion; Ignition coil or spark plug wire fault affecting cylinder 4; Mechanical issue such as low compression from worn rings, valves, or a faulty lifter on cylinder 4; Contaminated engine oil or fuel affecting injector performance on that cylinder; Exhaust leak near the cylinder 4 port affecting the oxygen sensor reading

DTC codes / P23xx · Ignition system and misfire / P230D

P230DCylinder 4 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance

P230D indicates that the powertrain control module (PCM) has detected an air-fuel ratio imbalance on cylinder 4 that has reached the adjustment limit during a balance test. The engine computer tried to equalize power contribution across all cylinders and found that cylinder 4 could not be corrected any further, meaning that cylinder is running significantly richer or leaner than the rest.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Rough idle or noticeable vibration, especially when the engine is cold or under light load
Slight hesitation or stumble during acceleration
Decreased fuel economy compared to normal driving
Occasional misfire sensation or shaking felt through the steering wheel or seat

Common causes, most likely first

Faulty fuel injector on cylinder 4, such as a clogged nozzle or internal leak
Vacuum leak at the intake manifold runner or injector O-ring specific to cylinder 4
Worn or fouled spark plug on cylinder 4 causing incomplete combustion
Ignition coil or spark plug wire fault affecting cylinder 4
Mechanical issue such as low compression from worn rings, valves, or a faulty lifter on cylinder 4
Contaminated engine oil or fuel affecting injector performance on that cylinder
Exhaust leak near the cylinder 4 port affecting the oxygen sensor reading

How to diagnose and fix it

Connect a scan tool and record freeze-frame data and any stored misfire counters for cylinder 4
Perform a visual inspection of the cylinder 4 ignition components, wiring, and injector connector
Swap the ignition coil and spark plug from cylinder 4 to another cylinder and recheck the balance test to see if the fault moves
Run a compression test and cylinder leak-down test on cylinder 4 to rule out mechanical problems
Check for vacuum leaks at the intake manifold and injector seals using a smoke machine or carburetor cleaner
Test the cylinder 4 fuel injector for resistance, spray pattern, and flow rate, and replace if faulty
Clear the codes and perform a road test with the scan tool monitoring cylinder balance to confirm the repair

What the balance test really reveals

A P230D can be set by a perfectly healthy cylinder if the balance test is run with low fuel pressure or a partially restricted fuel filter, so always verify fuel delivery before condemning the injector.
Many technicians replace the cylinder 4 injector only to find the real cause is a worn spark plug or coil that was marginal and failed the balance test under load.
The code does not always mean the cylinder is misfiring; it means the PCM ran out of adjustment range, which can happen with a slightly lean condition that is not severe enough to trigger a misfire code.
A dirty mass airflow sensor or a failing upstream oxygen sensor can skew the balance test results across all cylinders, making cylinder 4 appear faulty when the problem is upstream.
On engines with variable valve timing, a sticking oil control valve can affect cylinder 4 balance without setting any other codes, so check VVT operation if ignition and fuel checks pass.

Can I keep driving with P230D?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, towing, or sustained high-speed driving because the imbalance can lead to overheating of the catalytic converter and further engine damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.