P0204: Cylinder 4 Injector A Circuit/Open

What does P0204 mean?

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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

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

Common causes

• High Connector at the cylinder 4 injector loose, corroded or with a broken or pushed-back pin
• Medium Injector coil open
• Medium Wire between module and injector open or chafed (heat, rodents)
• Low Injector supply missing (fuse, relay) – then usually several cylinders at once
• Low Driver stage in the engine module faulty

Likelihood is a general estimate across vehicles; your make and model may differ.