Faulty ignition coil or spark plug specific to cylinder 4; Leaking or clogged fuel injector on cylinder 4; Vacuum leak at the intake manifold runner for cylinder 4; Mechanical issue such as low compression, worn rings, or valve problems on cylinder 4; Exhaust leak near the cylinder 4 port affecting the oxygen sensor signal; Contaminated or degraded engine oil affecting variable valve timing components; Wiring or connector fault in the cylinder 4 injector or ignition circuit

DTC codes / P21xx · Fuel and air metering / P219F

P219FCylinder 4 Air-Fuel Ratio Imbalance

Q: What does code P219F mean?

Cylinder 4 Air-Fuel Ratio Imbalance. P219F indicates that the powertrain control module (PCM) has detected a significant air-fuel ratio imbalance on cylinder 4, meaning that cylinder is not contributing its fair share of power or is running noticeably richer or leaner than the rest of the engine. The PCM typically makes this determination by comparing crankshaft speed fluctuations or individual exhaust oxygen sensor readings against learned values for the other cylinders.

P219F indicates that the powertrain control module (PCM) has detected a significant air-fuel ratio imbalance on cylinder 4, meaning that cylinder is not contributing its fair share of power or is running noticeably richer or leaner than the rest of the engine. The PCM typically makes this determination by comparing crankshaft speed fluctuations or individual exhaust oxygen sensor readings against learned values for the other cylinders.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering

Symptoms you may notice

Often no symptoms besides the warning light, especially in early stages
Noticeable engine misfire or rough idle that may worsen under load
Reduced fuel economy and a rich-smelling exhaust
Hesitation or stumble during acceleration
Shaking or vibration felt through the steering wheel or seat
In some cases, a flashing check engine light indicating a catalyst-damaging misfire

Common causes, most likely first

Faulty ignition coil or spark plug specific to cylinder 4
Leaking or clogged fuel injector on cylinder 4
Vacuum leak at the intake manifold runner for cylinder 4
Mechanical issue such as low compression, worn rings, or valve problems on cylinder 4
Exhaust leak near the cylinder 4 port affecting the oxygen sensor signal
Contaminated or degraded engine oil affecting variable valve timing components
Wiring or connector fault in the cylinder 4 injector or ignition circuit

How to diagnose and fix it

Perform a visual inspection of cylinder 4 ignition components and wiring for damage or corrosion
Swap the ignition coil and spark plug from cylinder 4 with a known-good cylinder to see if the misfire moves
Use a scan tool to check misfire counters and fuel trim data to confirm which cylinder is affected
Run a compression test and cylinder leak-down test to rule out mechanical faults
Check fuel injector operation with a noid light or injector balance test, and inspect for leaks
Smoke-test the intake system to locate vacuum leaks near cylinder 4
Verify exhaust system integrity and oxygen sensor operation with a scan tool and oscilloscope if available

Cylinder 4 imbalance often misdiagnosed

A P219F can be set by a vacuum leak that affects only one intake runner, so a full intake smoke test is essential before replacing parts.
Technicians sometimes replace the oxygen sensor when the real problem is a leaking injector or a failing ignition coil that only shows up under load.
Low compression on cylinder 4 from a worn cam lobe or collapsed lifter can mimic an injector fault, so mechanical testing should not be skipped.
The code may appear alongside misfire codes like P0304, but the absence of a misfire code does not rule out a mechanical issue.
Fuel contamination or a restricted fuel filter can cause lean conditions that affect one cylinder more than others, leading to this code.

Can I keep driving with P219F?

You can drive cautiously to a repair shop if the check engine light is steady and the engine runs smoothly, but avoid heavy acceleration or towing. If the light flashes or the engine misfires noticeably, stop driving to prevent catalytic converter 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.