OBD codes / P0204
P0204
SeriousInjector Circuit/Open - Cylinder 4
P0204 deserves prompt attention. Unburned fuel from a non-firing cylinder 4 flows straight into the exhaust and can overheat the catalytic converter, turning a modest electrical repair into an expensive one. Drive lightly, skip the highway pulls, and if the check-engine light flashes, stop.
What this code means
P0204 is the engine computer reporting that the cylinder 4 injector circuit isn't behaving electrically — it detected an open, a short, or resistance outside the expected window when it tried to pulse that injector. This code lives in the wiring-and-coil world, not the fuel-flow world: a clogged injector would not set it, because a clog doesn't change the circuit's electrical properties. In practice the fix is most often at the connector (corrosion, a loose terminal, or a plug knocked off during other work), next most often in chafed or broken harness wiring, and after that a failed winding inside the injector. The computer's own injector driver fails only rarely. Since cylinder 4 usually stops firing, the misfire code P0304 is a common companion.
Symptoms you might notice
- Cylinder 4 misfire — P0304 frequently stored with this code
- Rough idle and vibration at stoplights
- Noticeable power loss; the engine feels flat
- Check-engine light, which can flash under an active misfire
- Longer cranking before startup on some engines
What it costs to fix
Typical range: $80–$550 · about ~0.5–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Fuel injector (single) | $50–$300 | ~0.5–2 hrs |
| Wiring / connector repair | $10–$60 | ~0.5–1.5 hrs |
On most inline four-cylinder engines cylinder 4's injector is easy to reach, keeping labor low. V engines that require intake-manifold removal push labor toward the high end. These ranges cover typical gasoline port and direct-injection engines; diesel injectors cost several times more.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0204 for my exact vehicle →
Frequently asked
I have both P0204 and P0304 — which do I fix?
They're two views of the same problem: P0204 is the electrical fault on the cylinder 4 injector circuit, and P0304 is the misfire that results when that cylinder gets no fuel. Repair the circuit fault and the misfire code should clear with it.
What's the first thing to check for P0204?
The injector connector. Unplug it, look for green corrosion, spread terminals, or a plug that wasn't fully clicked in — especially if anyone recently worked on the engine. It's the most common cause and the cheapest fix.
Is it okay to drive with P0204?
Gently and briefly, if the light is steady. The risk isn't being stranded so much as feeding raw fuel to the catalytic converter, which can be ruined by a sustained misfire. A flashing light means active converter damage — stop driving.
What will fixing P0204 cost?
Often very little — connector and wiring repairs are cheap. If the injector itself has failed, expect a moderate part price plus half an hour to two hours of labor, with V engines that need the intake removed sitting at the top of that range.
Seeing P0204 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0204 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0204 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.