Diagnostic article Generic OBD-II
P2B03: Cylinder 4 injection pulses without the expected opening signature
P2B03 evaluates injector movement through coil-voltage feedback, rather than assuming that an electrical command delivered fuel.
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Documented application
2025 GM 03B documented monitor only; module and calibration applicability must be matched to the vehicle.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P2B03 targets cylinder 4 injection-pulse performance in the GM 03B monitor. The controller looks for the voltage-feedback signature produced when the injector's pintle or armature moves. This separates a commanded injection from evidence that the injector actually opened.
What the missing-pulse test measures
The ECM measures voltage feedback across the injector's enable and command wiring and converts that information into an opening-magnitude value. The published failure routes are absence of a detectable opening magnitude or a measured magnitude below the applicable missing-pulse limit.
The monitor requires the small-pulse diagnostic to be enabled and fuel-pulse voltage-feedback data to be ready. Its sampling is tied to cylinder events, with a listed 50-to-100-sample qualification range. Those are event samples, not a universal number of seconds or a required number of cranking attempts.
Why the distinction is useful
A commanded pulse or an electrical-continuity result does not independently establish the movement signature evaluated here. Equally, the code does not measure the injector's delivered fuel quantity directly. Retain pulse-command context, feedback validity and any available missing-pulse results before interpreting a cylinder contribution complaint.
The source uses a supporting calibration table for the opening-magnitude threshold; this article does not invent an externally measurable coil voltage from that converted value. Confirm the exact cylinder numbering and controller procedure before testing. Injector circuits and high-pressure fuel work require the prescribed equipment and safe service method. Verification should demonstrate valid feedback during an enabled cylinder-event evaluation, not merely a cleared code.
Source and applicability
2025 GM 03B documented monitor only; module and calibration applicability must be matched to the vehicle. GM PDF, page 863.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
Cylinder 4 Injection Pulse Performance
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT