P0203 - Injector Circuit - Cylinder 3
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0203 is a diagnostic trouble code (DTC) for an injector circuit malfunction specifically on cylinder 3. The Engine Control Module (ECM) monitors the continuity and voltage of the injector circuit. When the ECM triggers the injector driver, it expects to see the voltage drop to near ground; when released, it expects a high-voltage inductive spike followed by battery voltage. If the logic circuit within the ECM detects a deviation from these expected parameters, such as an open circuit or high resistance, P0203 is stored.
Possible Causes
Defective fuel injector on cylinder 3 (internal electrical failure or open circuit)
Wiring harness damage, chafing, or corrosion in the connector
Loose connection or bent pins in the electrical connector
Failed injector driver circuit inside the Engine Control Module (ECM)
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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