P058A: battery-monitor internal checks, not a battery-capacity verdict

P058A reports battery-monitor performance. The 03A ECM example receives an internal-fault indication over LIN. The more detailed 04B BCM example describes an intelligent battery sensor, or IBS, testing its own reference, calibration data, memory checksums and wakeup timer.

An internal result travels over LIN

In the BCM implementation, the IBS performs the checks once on LIN wakeup and communicates the result within six seconds. A fault first noticed after waking the vehicle can therefore be associated with that self-test sequence rather than with a sudden change in battery capacity.

Both examples require usable communication. The BCM table excludes active lost-communication and incorrect-message-counter faults, while the ECM example excludes bus-off or battery-module communication faults. A module that cannot communicate presents a different evidence problem from one that communicates an internal failure.

Applying the result

Confirm which controller stored the code and whether its enabling conditions were met. The ECM example requires reference voltage above 9 volts and a valid ambient temperature within its stated range; the BCM example enables above 11 volts with disabling hysteresis below 10 volts. These must not be blended into one threshold.

The code is not a published battery load-test result and does not identify which internal IBS check failed. Verification should establish a successful enabled self-test with valid communication. Use the applicable sensor and module service information before drawing a component-replacement conclusion.

Source and applicability

Documented monitors in gm-2025-03a, gm-2025-04b, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 347. GM 2025-04b, page 67.