P0203: Cylinder 3 Injector A Circuit/Open

P0203 reports an electrical fault, mainly an open circuit, in the injector circuit of cylinder 3. The engine module watches each injector output: GM flags an open circuit at an impedance of 200 kΩ or more – on direct injection and diesel engines in 10 of 20 or 5 of 10 samples and with the warning light in the first trip, on some port-injected engines only after two trips. Ford's port injection reads a fault bit from the driver chip that covers open, short to ground and short to voltage alike; Ford diesels report only the open circuit here and shorts as P0267/P0268. On direct injection the affected injector is switched off; the cylinder misfires.

Cylinder 3 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

• Check engine light on
• Misfire and rough running, misfire code P0303
• Loss of power, rough idle
• Limp mode possible on diesel and direct injection

Most likely causes

• Connector at the cylinder 3 injector loose, corroded or with a broken or pushed-back pin
• Injector coil open
• Wire between module and injector open or chafed (heat, rodents)
• Injector supply missing (fuse, relay) – then usually several cylinders at once
• Driver stage in the engine module faulty

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the connector and wiring of the injector indicated
2. Check the continuity of the wire between the component and the control module.
3. Measure the resistance and compare it with the manufacturer's specification
4. Check the control signal with an oscilloscope; on direct injection or diesel engines, leave this to a repair shop because of the high voltages
5. On diesels, check the per-cylinder injection corrections

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0203 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 2: Fuel injection
• 03: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0203?

Limit driving to what is essential: a cylinder without injection vibrates and the car responds worse. If an injector sticks open, it can fill the cylinder with fuel, so shut off the engine if you smell gasoline.

What causes code P0203?

The most common causes are: connector at the cylinder 3 injector loose, corroded or with a broken or pushed-back pin; injector coil open; wire between module and injector open or chafed (heat, rodents).

Related codes

• P0267Cylinder 3 Injector A Circuit Low
• P0268Cylinder 3 Injector A Circuit High
• P02F0Cylinder 3 Injector Circuit Range/Performance
• P0303Cylinder 3 Misfire Detected
• P0300Random/Multiple Cylinder Misfire Detected
• P020CCylinder 3 Injection Timing

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
• gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
• fordservicecontent.com: obd summary diesel 2023

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.