P0204: Injector Circuit/Open - Cylinder 4
The engine computer has found an electrical problem in the fuel injector circuit for cylinder 4, so that cylinder may not be getting fuel.
What P0204 means
When P0204 sets, the computer has caught a fault in the cylinder 4 injector circuit: open, shorted, or missing the normal voltage spike when the injector closes. That cylinder will likely misfire, often with a P0304 at the same time. On inline four cylinder engines, cylinder 4 sits at the end nearest the transmission, where harnesses route around brackets and can be pinched or rubbed. A failed injector coil or a corroded connector are just as likely. KBB groups P0200 through P0204 together and says experts do not recommend driving with them, since an engine that misfires for long can be damaged. Shops measure injector resistance, check the power feed with the key on and use a noid light to see the pulse from the computer. If the injector clicks and the pulse is good but the cylinder still misfires, they move on to ignition or compression tests. Otherwise, the repair is usually an injector or a wiring fix.
Common symptoms
- Check engine light on
- Misfire on cylinder 4, often with P0304
- Rough idle and shaking
- Loss of power
- Worse gas mileage
Most common causes
- Open or shorted fuel injector coil
- Broken or corroded injector connector
- Damaged wire between the computer and the injector
- Harness damage near the back of the engine or transmission
- Engine computer injector driver failure (rare)
What to check yourself first
On inline four engines, cylinder 4 sits at the end nearest the transmission. Unplug the cylinder 4 injector connector and look for broken locks, green corrosion or pushed out pins. With a meter, measure injector resistance and compare it to a neighboring injector; a reading of zero or open points to a bad injector.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace fuel injector | $768-$953 | Replace if the injector resistance is out of spec or it does not click. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | RepairPal warns injectors and computers are often replaced when the wiring is the real problem. |
| Check engine light diagnosis at a shop | $125-$183 | Includes a noid light test to check the injector pulse at the connector. |
| Replace engine control module (ECM/PCM) | $1,122-$1,192 | Only if the injector driver inside the computer is confirmed dead. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0200 Injector Circuit/Open
- P0304 Cylinder 4 Misfire Detected
- P0203 Injector Circuit/Open - Cylinder 3
- P0201 Injector Circuit/Open - Cylinder 1
- P0171 System Too Lean (Bank 1)