P0204 Code: Injector Circuit Malfunction - Cylinder 4

🟠 Moderate severity · drivable

Drivable short-term, but cylinder 4 may misfire and raw fuel can hurt the catalytic converter — fix it soon.

What P0204 means

The engine computer has flagged an electrical fault in the fuel injector circuit for cylinder 4, so it can't control that injector. This is a wiring/circuit problem rather than a fuel-pressure issue, and it often appears alongside a cylinder 4 misfire (P0304) because cylinder 4 isn't getting proper fuel.

Symptoms

Check engine light on (may flash)
Rough idle or misfire on cylinder 4
Loss of power
Poor fuel economy

Common causes

most common: Faulty fuel injector on cylinder 4 (internal electrical fault)
common: Damaged wiring or a loose connector at the cylinder 4 injector
less common: Injector driver failure in the engine computer (PCM)

How to fix it

Fix	DIY?	Typical cost
Test the cylinder 4 injector circuit with a noid light	Yes	$10–30
Swap the cylinder 4 injector to another cylinder to confirm the fault follows it	Mechanic	$100–300
Replace the cylinder 4 fuel injector	Mechanic	$100–300
Repair damaged injector wiring or connector	Mechanic	$50–150

Frequently asked questions

Is P0204 a wiring or fuel issue?

Wiring/circuit. P0204 means the injector circuit can't be controlled electrically, which often leads to a cylinder 4 misfire (P0304).

How do I test a P0204?

Plug a noid light into the cylinder 4 injector connector. A flashing light means the computer is commanding it; no flash points to wiring or the computer driver.

Can I drive with a P0204?

Short distances only — cylinder 4 may misfire and push unburned fuel into the catalytic converter.

Related codes

P0304

P0304 Code: Cylinder 4 Misfire Detected

P0200

P0200 Code: Injector Circuit Malfunction

P0264

P0264 Code: Cylinder 2 Injector Circuit Low

Updated 2026-08. This page is informational and not a substitute for professional diagnosis.