Fault code P0203 – a step-by-step guide to diagnosing and fixing it

Error code P0203 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a fault in the injection valve of the third cylinder. This DTC (Diagnostic Trouble Code) indicates a problem with the electrical circuit of the fuel injector of cylinder 3, which can lead to engine performance problems.

What can cause this error code?

• Defective injector cylinder 3
• Damaged wiring to the injector
• Corroded or loose plug connections
• Defective engine control unit (ECU)
• Short circuit in the injector circuit
• Broken ground wire
• Defective fuel pump or low fuel pressure
• Clogged fuel filter

What symptoms occur in parallel with fault code P0203?

• Engine running smoothness: The engine runs unevenly and jerks, especially at idling speed
• Loss of power: Noticeable reduction in engine power when accelerating
• Increased fuel consumption: Consumption increases significantly
• Starting problems: The vehicle is harder to start or requires several attempts to start
• Exhaust odor: Unburned fuel can smell in the exhaust gas
• Misfiring: The engine fires irregularly, especially under load

How can the problem with fault code P0203 be rectified?

• Repairing fault code P0203 requires a systematic diagnosis of the injector circuit.
• Replace injector valve cylinder 3: Replace the defective injector valve with a new or reconditioned spare part, replacing the seals in the process
• Check and repair wiring and plug connections: Inspect all cables to the injector for damage, clean corroded contacts and replace defective cables
• Diagnose the engine control unit and replace if necessary: Test ECU with professional diagnostic software and replace with a programmed replacement unit if defective
• Check and clean the fuel system: Measure fuel pressure, change filter and check fuel lines for blockages
• Measure injector resistance and test electrical connections: Check the resistance of the injector with a multimeter and perform a continuity test on the circuit