P0204: The fuel injector circuit for cylinder 4 has a fault
Injector Circuit Malfunction -- Cylinder 4
There is a fault in the cylinder 4 fuel injector circuit, which causes a misfire. Get it checked today. If the light is flashing, stop driving: raw fuel can destroy the catalytic converter within minutes.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
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 the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Wiring or connector repair
- Fuel injector replacement (single)
- PCM diagnosis and replacement
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 reads P0204 alongside any misfire codes for cylinder 4, so you can confirm the injector fault is causing a misfire before any parts come off. Get Lewis on the App Store or Google Play.
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.
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