P0203
P0203 Injector Circuit/Open Cylinder 3
P0203 is a generic OBD2 powertrain diagnostic trouble code for injector circuit/open cylinder 3. The code identifies the system or circuit the engine computer flagged, but diagnosis still depends on vehicle symptoms, freeze-frame data, and related codes.
How urgent is P0203?
Injector circuit and fuel-delivery faults can create misfires that damage the catalytic converter. Diagnose quickly if the engine runs rough.
Common symptoms
- Check engine light
- Misfire
- Rough idle
- Poor acceleration
- Fuel smell
Likely causes
- Injector circuit fault
- Clogged or leaking injector
- Damaged connector
- Open or shorted wiring
- PCM driver fault in rare cases
What to check before replacing parts
1
Check injector connector and wiring
2
Verify injector pulse
3
Listen for injector operation
4
Run injector balance testing
5
Check for cylinder-specific misfire codes
Use the code with symptoms
A code points at the system, not always the failed part. Add your vehicle, mileage, symptoms, and whether the check engine light is steady or flashing so the AI diagnostic can narrow the next step.