P0204: Cylinder 4 Injector A Circuit/Open

P0204 reports an electrical fault, mainly an open circuit, in the injector circuit of cylinder 4. 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 P0270/P0271. On direct injection the affected injector is switched off; the cylinder misfires.

High severity. Can I keep driving?Make only the shortest trip needed to get the car somewhere safe: the engine loses power and, if the circuit leaves the injector open, unburned fuel can damage the catalytic converter. If the check engine light flashes, stop and do not continue.

Cylinder 4 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 P0304
Loss of power, rough idle
Limp mode possible on diesel and direct injection

Most likely causes

Connector at the cylinder 4 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.

Check the connector and wiring of the injector indicated
Check the continuity of the wire between the component and the control module.
Measure the resistance and compare it with the manufacturer's specification
Check the control signal with an oscilloscope; on direct injection or diesel engines, leave this to a repair shop because of the high voltages
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 P0204 means

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

Frequently asked questions

Can I keep driving with code P0204?

Make only the shortest trip needed to get the car somewhere safe: the engine loses power and, if the circuit leaves the injector open, unburned fuel can damage the catalytic converter. If the check engine light flashes, stop and do not continue.

What causes code P0204?

The most common causes are: connector at the cylinder 4 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

Sources

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.