P2156: Group D supply-low is assessed while its high-side driver is on

P2156 is the fuel injector group D supply-circuit-low entry. The cited GM implementation calls the monitored channel injector 4's high-side driver. The strategy classifies a ground-directed electrical fault from its feedback while that driver is powered on.

An energized-driver comparison

The controller uses its own acceptable voltage range to assess the output. An off-state measurement is not equivalent, because a deliberately inactive driver can have different expected feedback. The code also does not say that fuel pressure is low; its subject is the electrical supply path represented by this output.

The listed enables require battery voltage of at least 11 V, engine runtime of at least one second and the specified P062B fault states to be absent. Ten failures within twenty samples, evaluated every 100 milliseconds, confirm the condition with one-trip reporting.

Preserve the output identity and its operating opportunity

Record the high-side command, feedback status, supply and applicable injector-driver faults together. If the wider injector-control diagnostic inhibits this assessment, the absence of another P2156 result cannot establish that the output passed.

The group-D label and the document's injector-4 name must be mapped through the actual controller configuration before choosing physical hardware. This table gives no connector pin or universal probe voltage and does not locate the ground-directed path in wiring, load or controller. Further electrical isolation requires the matching service procedure rather than a fuel-system replacement based on the code alone.

Source and applicability

2025 GM 03B documented monitor only. Vehicle, engine and controller calibration applicability must be established separately; no model fitment is inferred from the file. GM PDF, physical page 789.