OBD-II · Engine and powertrain (P)
P0204
Injector circuit cylinder 4
What it means
The engine computer sees an electrical fault in cylinder 4's injector circuit (open, short or wrong current). This applies to petrol and diesel engines; diesel common-rail injectors may be solenoid or piezo type.
Symptoms
- misfire or rough running on cylinder 4
- loss of power
- smoke (diesel)
- engine warning light, sometimes limp mode
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | loose, corroded or oil-contaminated injector connector |
| 02 | damaged injector wiring (on some engines it runs under the valve cover and suffers from heat and oil) |
| 03 | failed injector coil or piezo stack |
| 04 | shorted harness affecting the injector group |
| 05 | engine computer driver fault (rare) |
What to check, step by step
- 01Check if other injector or injector group codes (P2146-P2151) are stored - several cylinders point to wiring or the engine computer.
- 02Inspect the connector for oil, corrosion and backed-out pins.
- 03Identify the injector type and follow its OEM electrical tests with ignition off and required discharge precautions. Use the specified resistance, insulation or capacitance test as applicable; do not apply solenoid-coil criteria to piezo injectors.
- 04With components isolated as specified, check harness continuity and shorts back to the engine computer; never unplug an injector while the engine is running.
- 05Replace an injector only if confirmed faulty; enter its correction code and perform adaptation if that engine and injector system require it.