P0203 — Injector Circuit/Open - Cylinder 3

What it means

An electrical fault has been detected in the control circuit of the cylinder 3 injector: the module sees an open circuit or a coil resistance outside the specification. Injection into that cylinder stops, so the cylinder produces no torque and the engine vibrates and loses power. Unburned mixture entering the exhaust distorts fuel trim on the whole bank.

Likely causes (most common first)

1. Loose or oxidised connector on the cylinder 3 injector
2. Broken conductor or insulation rubbed through in the engine harness
3. Open winding in the injector itself
4. Interruption in the common supply line to the injectors, fuse or relay
5. Water ingress into the connector causing corrosion of the terminals
6. Failed injector driver channel in the engine control module

Can you drive with it?

Drive only to the workshop and gently: continuous misfire from the dead cylinder destroys the catalytic converter within a few dozen kilometres.