Comprehensive diagnostic guide for OBD-II code P0202

Cylinder 2 Injector Circuit/Open

Overview

• What the code means: P0202 is an OBD-II powertrain diagnostic trouble code indicating an open , which aligns with the standard interpretation of P0202 as a cylinder 2 injector circuit issue. Citation: Open Source OBD2 code entry; standard OBD-II mapping and Wikipedia's OBD-II Powertrain Codes context. Citations: Wikipedia OBD-II: Diagnostic Trouble Codes; Wikipedia OBD-II: Powertrain Codes; Open Source injector code entry.
• Context: DTCs like P0202 are part of the OBD-II diagnostic framework and classified under powertrain (engine) codes. Citations: Wikipedia OBD-II: Diagnostic Trouble Codes; Wikipedia OBD-II: Powertrain Codes.

Symptoms

• MIL Illumination: Check Engine Light active due to the P0202 code.
• Rough idle or misfire symptoms that are localized to cylinder 2 (engine may feel the misfire or stumble when cylinder 2 is commanded as active).
• Reduced engine power or drivability issues (especially under load or during acceleration).
• Possible accompanying misfire codes such as P0302 could appear if the injector circuit fault causes a loss of cylinder 2 combustion.
• Fuel economy may degrade while the MIL is active.

Note: The above symptom set reflects typical field observations when injector circuit faults are present and aligns with general DTC behavior described in OBD-II references. If you have a P0202 but no misfire symptoms, you still should diagnose the injector circuit since the PCM is not energizing or reading the injector for cylinder 2.

Probable Causes

Because the sources don't provide NHTSA complaint statistics for P0202, the probability guidance here comes from standard ASE field experience and automotive diagnostic practice:

• Injector circuit open (internal fault or broken coil in cylinder 2 injector): 30-50%
• Wiring harness or connector issue to injector 2 (damaged insulation, loose/dirty pins, corrosion): 15-35%
• PCM injector driver/output failure or intermittent control signal: 5-15%
• Power supply or grounding issue affecting injector/PCM (battery voltage drop, bad ground strap, corrosion): 5-15%
• External or incidental issues (recent service, water intrusion, wiring harness routing damage): 5-10%

Step-by-Step Diagnosis

1) Confirm the code and collect data

• Use a capable OBD-II scan tool to confirm P0202 (Cylinder 2 Injector Circuit/Open).
• Record freeze-frame data: engine coolant temperature, absolute load, engine RPM, vehicle speed, and any other active codes. These help assess operating conditions when the fault occurred.
• If available, review injector pulse width/current for cylinder 2 on live data to see if the PCM is commanding the injector and whether current is present.

2) Cross-check with related issues

• Check for misfire codes (P0302, P0300, etc.) that could be associated with an injector issue.
• Review recent service history for injector changes, wiring repairs, or water intrusion in the engine bay.

3) Visual and mechanical inspection

• Inspect the injector 2 electrical connector for corrosion, bent/pushed pins, damaged seals, or improper locking.
• Inspect the injector wiring harness for insulation damage, abrasion, chafing, or routing that could cause a short to ground, short to power, or open circuit.
• Check for signs of oil or fuel leakage around the injector or intake manifold, which can indicate injector or seal problems.

4) Electrical testing (injector 2 circuit)

• Resistance (ohm) test of injector 2 coil with an ohmmeter; compare measured value to factory spec. Abnormal resistance (much higher or lower than spec) indicates an internal injector fault.
  • If resistance is out of spec, replace the injector.
• Inspect injector supply voltage and ground when the ignition is on and the engine is cranking/running (as applicable to the vehicle's system):
  • Use back-probing or a suitable probe to verify:
    • One side of the injector coil bridge is supplied with a constant 12V (or system voltage) when the ignition is on.
    • The other side is being switched to ground (or PWM) by the PCM during operation.
  • Use a noid light or an oscilloscope to verify that the PCM is providing pulses or activity on the injector circuit corresponding to cylinder 2 when commanded.
• Check continuity of the wiring from the PCM injector driver to injector 2: look for opens, shorts to ground, or shorts to 12V in the harness.

5) Functional testing and fault isolation

• Swap test (advanced diagnostic step to differentiate injector vs wiring/PCM):
  • Swap injector 2 with injector 3 (or another cylinder with a known-good injector) and clear codes, then re-test:
    • If P0202 follows the injector (code moves to P0203), injector 2 is likely faulty.
    • If P0202 remains on cylinder 2 despite the swap, wiring or PCM circuit for cylinder 2 is likely the issue.
  • After the swap test, recheck the system with the scan tool and drive the vehicle to verify the fault is reproducible and localized.
• If injector 2 tests out electrically and the symptoms persist, investigate PCM output integrity or module grounding as a potential root cause.

6) Post-repair verification

• After repairing any wiring or replacing injector 2, clear DTCs and perform a road test or drive cycle to verify the code does not return.
• Ensure the engine runs smoothly with cylinder 2 contributing normally (no rough idle, no loss of power, and no misfire indications on cylinder 2).

Tools Needed

• OBD-II scan tool capable of live data and freeze-frame retrieval
• Digital multimeter (DC) for resistance/continuity tests
• Noid light or injector signal tester
• Sufficient inline or back-probe leads for connector testing
• Optional: oscilloscope or injector pulse width reader for advanced waveform analysis
• Manufacturer service information/specifications for injector coil resistance and PCM drive behavior (as available)

Safety Considerations

• Disconnect the battery or follow proper battery safety procedures when unplugging or reconnecting electrical connectors in the engine bay.
• Wear eye protection and follow safe handling procedures when probing live circuits, and avoid shorting pins or applying external power to injector circuits.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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