P0203 Injector Circuit Malfunction - Cylinder 3

P0203 points to an injector circuit malfunction on cylinder 3. The code identifies the injector control circuit that needs electrical testing.

Code status

Needs verification

Not yet verified against SAE J2012_202509 / J2012DA. Treat unverified rows as a lookup aid, not repair authority.

System: Injector
Scope: iso-sae-controlled-p0
Standard: SAE J2012 / ISO 15031-6
Source: legacy-import

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not treat P0203 as a fuel-quality or spark-plug issue first; the named path is the cylinder 3 injector circuit.

Useful checks before replacing parts

Inspect cylinder 3 injector connector condition, terminal tension, wiring continuity, power feed, and control signal.
Compare injector current, resistance, or balance results against known-good cylinders when the vehicle supports it.
Use misfire data and fuel trims to separate injector-circuit failure from fuel delivery or compression problems.

Related OBD-II codes

These nearby injector entries can help compare wording and fault area. They may share the same verification status as the source database.