Diagnostic article Generic OBD-II
P2671: Supply B high is a shutdown switch test in this controller
P2671 checks whether transmission HSO2 remains too high after it is disabled, with the result stored for the next startup.
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Documented application
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred.
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.
The P2671 monitor in this transmission table tests high-side output two after it is disabled during powerdown. A voltage above 70% of battery voltage is the listed shorted-switch criterion. This differs from the related open-load check, which uses a different test configuration and threshold.
Timing explains an apparently normal startup
The controller saves the shutdown failure in nonvolatile memory and reports it at the next startup. Finding a normal value after the code appears does not establish that the earlier shutdown test passed. The relevant interval is at least 60 ms, with battery change during the test below 1.5 V.
The source also restricts supply voltage and disables the check for P0882 or P0883. These conditions affect whether a follow-up shutdown can provide meaningful confirmation.
Evidence to keep
Record the HSO2 shutdown-test result and whether the output was actually disabled during the observation. A high voltage while an output is intentionally powered is a different condition. The code identifies a high-side switch-path failure class in this calibration, not a universal actuator location. Applicable service information is necessary to distinguish the output stage from its connected circuit before selecting a repair.
Document scope and source
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.
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
Actuator Supply Voltage B Circuit High
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