P0B56: Block-six low sensing is qualified by block seven as well

P0B56 is assigned to block-six voltage sensing in the cited GM table. Its low-limit condition requires block six below 2V and block seven below 2V. Reading only the named block misses an explicit part of the controller's decision.

A synchronized pair matters

The battery controller must be in run mode with its low-voltage supply in the accepted range and P0A1F inactive. The paired condition is then evaluated through 15 failing samples out of 20 at 100ms intervals.

Two low readings taken at different times do not establish that the required pair existed together. Preserve timestamps or a synchronized trace when available, especially if the event is intermittent and one channel has already recovered during later inspection.

Keep signal evidence separate from physical conclusions

The source does not reveal the actual sense-wire topology or prove that adjacent physical modules share a failed connection. It also does not establish that the physical blocks are depleted or de-energized. Those conclusions need the correct battery diagram and approved service tests.

Record related block-six rationality/high-limit codes and other pack-sensing faults before clearing them. A qualified high-voltage technician must carry out any physical investigation using prescribed isolation and absence-of-voltage verification. The generic low-circuit label and a low scan display are not substitutes for that safety process.

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 225.