P2B03 — Cylinder 4 Injection Pulse Performance

Diagnostic algorithm

1. Retrieve all codes and freeze frame data. Note conditions when code set (engine temp, RPM, load).
2. Perform a visual inspection of cylinder 4 injector connector, wiring harness, and related grounds. Repair any obvious damage.
3. With ignition off, measure injector coil resistance at the connector and compare to spec. Replace if out of range.
4. Backprobe the injector connector with a noid light or oscilloscope while cranking/running to confirm injector drive pulses and waveform. Observe pulse width and shape.
5. Verify constant battery voltage at the injector power feed and check the driver ground/back to the ECM while operating.
6. Check fuel rail pressure and regulator operation at key-on, idle, and under load. Repair fuel system faults if pressure is low or fluctuating.
7. Swap the suspect injector with a known good injector from another cylinder. Clear codes and run to see if the fault follows the injector (if it follows, replace injector).
8. If the fault remains on cylinder 4 after a swap, suspect wiring between the ECM and injector or the injector driver in the ECM. Perform continuity and short-to-ground/power checks of the harness.
9. If wiring checks good, inspect ECM injector driver output with an oscilloscope. Replace ECM only after confirming driver failure and ruling out wiring and injector.
10. If electrical tests pass, perform mechanical checks on cylinder 4 (compression or leak-down test) and clean/test fuel injector flow as needed.
11. After repairs, clear codes and perform a road/test cycle to confirm the code does not return and drivability is restored.