Fuel & air metering · Powertrain · generic (SAE-defined)
P0204: Injector Circuit/Open - Cylinder 4
P0204 means the engine computer has found an electrical problem, commonly an open circuit, in the cylinder 4 fuel injector circuit.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0204 sets
The powertrain control module (PCM) monitors the cylinder 4 injector control circuit while commanding the injector on and off. If it cannot see the expected electrical behavior, due to an open, short or failed driver, it stores P0204. The exact method is manufacturer-specific.
Common causes of P0204
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Faulty cylinder 4 fuel injector winding
- Broken or shorted wire in the cylinder 4 circuit
- Connector corrosion or poor terminal tension
- Loss of injector supply voltage
- PCM injector driver failure
P0204 symptoms
- Check engine light on, possibly flashing
- Rough idle and vibration
- Reduced acceleration
- Cylinder 4 misfire code P0304 may also appear
How P0204 is diagnosed
- Scan for codes and note any related misfire or injector codes.
- Inspect the cylinder 4 injector connector and harness.
- Measure injector resistance and compare with the other injectors.
- Use a noid light to check for an injector pulse.
- Check the injector supply voltage and continuity of the control wire to the PCM.
Typical fixes for P0204
- Replace the cylinder 4 fuel injector
- Repair the circuit wiring or connector
- Restore injector power by fixing a fuse or relay issue
- Repair or replace the PCM if the driver is faulty
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0204 FAQ
What does code P0204 mean?
P0204 means the engine computer has found an electrical problem, commonly an open circuit, in the cylinder 4 fuel injector circuit. The standard definition is "Injector Circuit/Open - Cylinder 4."
Can I drive with a P0204 code?
Drive only if necessary and only a short distance. If the cylinder 4 injector is not working, the resulting misfire can overheat the catalytic converter, and a flashing check engine light is a sign to stop.
Can a single bad connector set P0204?
Yes. A connector that has loosened or corroded can interrupt the circuit and set the code, even if the injector itself is fine.
If several injector codes appear at once, what does it mean?
Multiple injector circuit codes together usually point to a shared problem, such as a lost power feed, a damaged harness section or a PCM issue, rather than several failed injectors.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.