P1203 Injector Circuit Fault (Cylinder 3) — Causes & Fix

What Does P1203 Mean?

P1203 is a manufacturer-defined (P1-series) injector circuit code for cylinder 3, used by several makes — notably Ford and PSA diesels — alongside or instead of the generic P0203. The diagnosis is identical: coil resistance, wiring and connector checks, then a swap test to confirm whether the injector or the circuit is at fault.

P1203 at a Glance

• What it means: Manufacturer-specific injector circuit fault for cylinder 3 (P1-series equivalent of P0203).
• Most common cause: Injector solenoid resistance out of specification, wiring short, or connector corrosion.
• Severity: Moderate to serious — the ECU may cut fuel to cylinder 3, causing a misfire.
• 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.