Is cylinder 4 the same location on every car?

No. Cylinder numbering conventions differ. On most inline four-cylinders, cylinder 4 is at the back or right end. On V-engines, numbering varies by manufacturer. Check a diagram for your specific engine.

Can a fuel injector test confirm P0204 is really the injector?

Resistance and balance rate tests can confirm a failed injector, but the circuit fault could still be wiring. Test both before ordering parts.

Why is the catalytic converter mentioned for an injector code?

A dead cylinder passes unburned oxygen and fuel into the exhaust. The converter overheats trying to burn it. Extended misfires are the most common way catalytic converters fail prematurely.

Codes › P0204

P0204: The fuel injector circuit for cylinder 4 has a fault

Injector Circuit Malfunction -- Cylinder 4

High severityCan you keep driving?

Drive with caution. If the light is flashing, stop driving now. A misfiring cylinder sends raw exhaust into the catalytic converter and can destroy it within minutes of continued driving.

What it means

P0204 is the cylinder 4 injector circuit fault. The PCM commands the injector to open and monitors the resulting current draw. When the electrical response is missing or wrong, this code sets. Cylinder 4 is particularly notable because on four-cylinder engines it is the last cylinder in the firing order, and its location at the end of the intake manifold can make it more susceptible to wiring harness pull or chafing. P0304 will typically accompany this code. Do not just replace the injector without first checking the harness.

Common causes

Wiring or harness damage to the cylinder 4 injectorOn inline four-cylinder engines, the cylinder 4 harness is stretched the farthest and most prone to chafing.
Failed injector solenoid coilThe coil inside the injector burns out. Resistance check will confirm.
Corroded or damaged connector at cylinder 4The back of inline engines often runs hotter, accelerating connector degradation.
PCM injector output driver failureRare. Only suspect after the injector and wiring are confirmed good.

What it costs

Wiring or connector repair$80 to $250
Fuel injector replacement (single)$150 to $400 installed
PCM diagnosis and replacement$500 to $1,200

Symptoms

Check engine light on, steady or flashing
Rough idle and vibration
Power loss and stumbling on acceleration
P0304 misfire code likely also stored
Possible fuel smell

What to do next

On a four-cylinder, cylinder 4 is at the far end of the engine. Check whether the harness has been rubbing against the timing cover or any bracket. Measure injector resistance and compare to spec. A common shop shortcut is to swap the cylinder 4 injector connector with cylinder 3 and see if the code follows the connector. If it does, the wiring or connector is the cause.

Lewis logs per-cylinder misfire data so you can confirm it is cylinder 4 misfiring before any parts come off. Download Lewis.

Related codes

FAQ

Is cylinder 4 the same location on every car?: No. Cylinder numbering conventions differ. On most inline four-cylinders, cylinder 4 is at the back or right end. On V-engines, numbering varies by manufacturer. Check a diagram for your specific engine.
Can a fuel injector test confirm P0204 is really the injector?: Resistance and balance rate tests can confirm a failed injector, but the circuit fault could still be wiring. Test both before ordering parts.
Why is the catalytic converter mentioned for an injector code?: A dead cylinder passes unburned oxygen and fuel into the exhaust. The converter overheats trying to burn it. Extended misfires are the most common way catalytic converters fail prematurely.