P0203: Injector Circuit/Open - Cylinder 3
The engine computer has found an electrical problem in the fuel injector circuit for cylinder 3, so that cylinder may not be getting fuel.
What P0203 means
P0203 is the cylinder 3 version of the injector circuit code. The computer has seen an open, short or missing feedback signal on the wire that switches the cylinder 3 injector. When the injector does not open, the cylinder gets no fuel and misfires, so P0303 often follows. A failed injector coil, a damaged connector and a broken or chafed wire are the usual causes. On engines where the injector harness runs across the top of the fuel rail, a wire can wear through on a sharp edge after years of engine vibration. Shops measure injector resistance and compare it with the others, since a coil that reads very different is suspect. They also confirm power at the connector and watch for the pulse with a noid light or scope. RepairPal notes that the most common misdiagnosis is replacing an injector or computer when the wiring is bad, so the harness deserves a close look before parts go in.
Common symptoms
- Check engine light on
- Misfire on cylinder 3, often with P0303
- 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
- Wire chafed against the intake or fuel rail
- Engine computer injector driver failure (rare)
What to check yourself first
Cylinder 3 is in the middle of most inline four engines. Unplug the cylinder 3 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
- P0303 Cylinder 3 Misfire Detected
- P0202 Injector Circuit/Open - Cylinder 2
- P0204 Injector Circuit/Open - Cylinder 4
- P0300 Random/Multiple Cylinder Misfire Detected