P0203
Cylinder 3 Injector A Circuit
Fuel injector circuit
Generic OBD-II
High
What it means
P0203 means the ECM has detected an electrical fault in the fuel injector circuit for cylinder 3. If the circuit is open or shorted, that injector may stop firing, so cylinder 3 misfires and the engine runs rough with reduced power. The most common causes are damaged wiring, a bad connector, or a failed injector solenoid on that cylinder.
High
Can I keep driving? Limited — if the injector circuit is dead, cylinder 3 won't fire and the engine runs rough and down on power; drive as little as possible.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle and noticeable misfire on cylinder 3
- Reduced power and hesitation
- Possible fuel smell or raw fuel in the exhaust
Common causes
Most likely first
- Damaged wiring or a connector open/short on the cylinder 3 injector circuit (most common)Likely
- Failed injector solenoid on cylinder 3Common
- Corroded or loose connector at the injectorCommon
- Faulty injector driver in the ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Inspect the injector's connector and wiring for damage, corrosion, or an open circuit.
- Measure the injector's coil resistance and compare it to the other injectors.
- Check that the injector is receiving a pulse from the ECM (noid light or scope).
- Swap the injector with an adjacent cylinder to see if the fault follows it.
- Replace the injector if it's failed; repair wiring or consider the ECM driver last. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0203?+
Not for long. A dead injector means one cylinder isn't firing, which runs raw fuel into the exhaust and can damage the catalytic converter.
Can I just clear P0203?+
It returns as soon as the ECM sees the circuit fault again. The wiring, connector, or injector has to be repaired first.
Related codes
Often seen with P0203
Read & clear P0203 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX