P2149: Reading injector group B supply faults through driver state

P2149 names injector group B supply voltage in the generic dictionary. In this GM source, the monitored entry is described as cylinder 2 injector “B” and concerns the high side of its driver circuit. That is the applicable documentary scope, not proof of a universal group layout.

The same code can represent opposite short directions

The monitor evaluates low voltage during the driver's off state as a short-to-ground pattern. It also evaluates high voltage during the on state as a short-to-supply pattern. These alternatives are joined in the row, which specifies two diagnostic events rather than a fixed number of elapsed seconds.

The consequence is practical: a fault code alone does not identify which direction the circuit failed. Nor does the generic “circuit/open” wording establish that an open wire is the detected condition.

What narrows the diagnosis

Retain the driver's electrical classification and its commanded state if those data are available. A high-side supply diagnosis should be separated from a fuel-pressure or injector-flow complaint; neither hydraulic measurement is the criterion used here.

The table references additional basic enable and inhibition rules. A test that was prevented from running is therefore not a passed supply-circuit test. For a particular vehicle, confirm the cylinder/channel mapping and actual supply topology before isolating wiring, load or driver behavior. The source does not tell which physical component must be replaced, and a guessed shared-injector arrangement could send the investigation to the wrong circuit.

Source and scope

2025 GM 25OBDG07A Part 2 monitor tables only; model, engine and transmission applicability are not established by the unresolved application-matrix filename join. These are documented monitor criteria, not a universal repair procedure. GM PDF, physical page 711.