P0203 Code: Injector Circuit Malfunction - Cylinder 3

🟠 Moderate severity · drivable

Drivable short-term, but cylinder 3 may misfire and unburned fuel can damage the catalytic converter — fix it soon.

What P0203 means

The engine computer has detected an electrical fault in the fuel injector circuit for cylinder 3, so it can't command that injector. P0203 is a circuit fault rather than a fuel-pressure issue, and it commonly pairs with a cylinder 3 misfire (P0303) because cylinder 3 isn't receiving the right amount of fuel.

Symptoms

Check engine light on (may flash)
Rough idle or misfire on cylinder 3
Loss of power
Poor fuel economy

Common causes

most common: Faulty fuel injector on cylinder 3 (internal electrical fault)
common: Damaged wiring or a loose connector at the cylinder 3 injector
less common: Injector driver failure inside the engine computer (PCM)

How to fix it

Fix	DIY?	Typical cost
Test the cylinder 3 injector circuit with a noid light	Yes	$10–30
Swap the cylinder 3 injector with another cylinder to see if the fault follows it	Mechanic	$100–300
Replace the cylinder 3 fuel injector	Mechanic	$100–300
Repair damaged injector wiring or connector	Mechanic	$50–150

Frequently asked questions

Is P0203 electrical or fuel-related?

Electrical. P0203 means the injector circuit can't be controlled. It typically triggers a cylinder 3 misfire (P0303) as a secondary effect.

What's the fastest way to check P0203?

Use a noid light on the cylinder 3 injector connector. If it flashes, the circuit and computer are commanding the injector; if not, the wiring or driver is at fault.

Can I drive with a P0203?

Briefly, but cylinder 3 may misfire and dump unburned fuel into the catalytic converter.

Related codes

P0303

P0303 Code: Cylinder 3 Misfire Detected

P0200

P0200 Code: Injector Circuit Malfunction

P0263

P0263 Code: Cylinder 1 Not Contributing Enough Power (Contribution/Balance)

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