DTC P0203: Cylinder 3 Injector Circuit/Open

In the intricate world of automotive diagnostics, diagnostic trouble codes (DTCs) serve as essential guides, illuminating potential issues within a vehicle’s systems. DTC P0203 takes center stage as an indicator of problems related to the Cylinder 3 Injector Circuit/Open. This comprehensive article delves into the causes, symptoms, inspection procedures, and effective solutions for diagnosing and resolving DTC P0203.

1. Causes of DTC P0203:

DTC P0203 emerges when the Engine Control Module (ECM) detects an open circuit or malfunction within the Cylinder 3 Injector Circuit. The underlying causes can encompass:

– Faulty injector: A malfunctioning or clogged injector can disrupt the fuel delivery to cylinder 3.

– Wiring and connector issues: Damaged or corroded wiring and connectors within the injector circuit can lead to open circuit conditions.

– Open injector circuit: A break in the injector circuit can result in a lack of signal transmission.

– ECM malfunction: An ECM glitch can lead to erroneous injector control signals.

2. Symptoms of DTC P0203:

Recognizing the symptoms associated with DTC P0203 assists mechanics in accurate diagnosis:

– Engine misfires: Cylinder 3 may experience misfires due to inadequate fuel delivery.

– Reduced engine performance: Insufficient fuel supply to cylinder 3 can lead to reduced power and efficiency.

– Illuminated Check Engine Light (CEL): DTC P0203 triggers the CEL to alert the driver of a potential problem.

3. Inspection of DTC P0203:

Thorough inspection techniques are crucial for pinpointing the root cause:

– OBD-II scan: Utilize an OBD-II scanner to retrieve the DTC and accompanying freeze frame data, offering insight into the conditions that activated the code.

– Visual examination: Inspect the Cylinder 3 injector wiring and connectors for visible damage or corrosion.

– Injector resistance check: Measure the resistance of the injector using a multimeter.

4. Resolving Causes of DTC P0203:

Addressing DTC P0203 requires specific actions tailored to the underlying issue:

– Injector replacement: Replace the malfunctioning injector with a new, high-quality unit that meets manufacturer specifications.

– Wiring and connector repair: Repair or replace damaged wiring and connectors to ensure accurate signal transmission.

– Injector circuit continuity test: Verify continuity within the injector circuit to identify any open circuits.

– ECM diagnosis: If an ECM malfunction is suspected, diagnose and address the issue through reprogramming or replacement.

5. Clearing DTC P0203:

After effectively resolving the underlying cause, clear the DTC from the ECM’s memory using an OBD-II scanner. This step confirms the issue’s resolution and prevents the CEL from reappearing.


DTC P0203, pointing toward problems in the Cylinder 3 Injector Circuit/Open, underscores the importance of proper fuel delivery for optimal engine performance. By comprehending its causes, recognizing its symptoms, employing meticulous inspection techniques, and implementing effective solutions, mechanics can accurately diagnose and rectify this issue. Ensuring reliable injector performance remains pivotal for achieving optimal engine functionality, fuel efficiency, and overall vehicle operation.