P058B: current-monitor performance includes stored sleep-time evidence

P058B concerns battery-current monitoring. The 04B BCM table identifies an open shunt condition diagnosed inside the intelligent battery sensor. Its result reaches the BCM over LIN; the broader 03A ECM summary simply describes a battery-module current fault.

Historical and continuous paths differ

The sensor can monitor the shunt while asleep and retain the result. The BCM reports that historical result within one second of LIN wakeup. Thus, a code appearing immediately after wakeup need not describe a new failure that began at that instant.

The continuous diagnostic uses four failed samples out of five, at sixteen seconds per sample, giving an eighty-second evaluation window. It does not run while the historical portion runs. A short observation immediately after waking the vehicle therefore cannot establish that the continuous test has completed successfully.

What the code does not measure

This monitor is concerned with the integrity of current measurement, not a published excessive-current or battery-capacity threshold. An unusual current PID may support further investigation, but it cannot by itself reveal whether the reported internal shunt fault is current or historical.

For the BCM example, valid IBS communication and appropriate system voltage are prerequisites. Record the storing module, wakeup timing, communication faults and test status before interpreting the current value. Verification should address both the historical indication and a completed continuous evaluation where applicable, using the exact vehicle procedure rather than replacing the battery solely because this code is present.

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 348. GM 2025-04b, page 68.