P0B48: Block-three circuit high checks the named input directly

P0B48 evaluates the high end of block-three voltage sensing in this GM controller. The documented threshold is an indicated value above 23V. Unlike block three's low-sense monitor, this high-limit entry does not require a simultaneous abnormal block-four reading.

The condition is channel-specific

The battery controller must be in run mode with the low-voltage supply accepted and the controller-performance fault absent. Fifteen qualifying samples within twenty, at 100ms intervals, form the failure decision.

The separate P0B46 rationality monitor compares scaled readings from blocks three and four against pack voltage. A high-limit result and a rationality result answer different questions, even when they concern some of the same measurement hardware.

Keep the original measurement identity

Capture block-three voltage, its validity information, pack voltage and companion sensing faults. A screen that shows only the highest block value may not preserve whether block three was the source of that maximum during the event.

The table provides no physical cell-group map, approved voltage test point or proof that a battery module must be replaced. A qualified technician must use the correct sensing diagram and service procedure to identify the cause. High-voltage isolation and verification are necessary before pack access; the monitor threshold is not a safe operating target or a reason to manipulate charging voltage.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, only the cited controller and monitor. These are historical calibration examples; individual vehicle, engine and hardware applicability is not established. GM PDF, page 223.