P0203 Injector Circuit Malfunction (Cylinder 3) — Causes & Fix

What Does P0203 Mean?

P0203 indicates the ECU has detected an electrical fault in the fuel injector circuit for cylinder 3. Cylinder 3 is the third from the timing belt end on inline engines. The diagnostic and repair approach is the same as P0201/P0202.

P0203 at a Glance

• What it means: The ECU has detected a fault in the fuel injector electrical circuit for cylinder 3.
• Most common cause: Faulty injector, wiring damage, or ECU driver fault.
• Severity: Moderate to serious — causes misfire on cylinder 3.
• Can you drive?: Short distances only. Prolonged driving risks DPF and catalytic converter damage.
• Typical repair cost: £100-£350 for injector replacement; £40-£100 for wiring repair.