P0B75: block 12 high sensing has its own filtered threshold

P0B75 describes a high-range voltage-sensing event for block 12 in the GM battery controller. The generic L designation should be mapped through the actual vehicle's service information. It should not be used to guess a terminal number or battery-module location.

Follow the high branch only

The block 12 measurement must exceed 23 V. GM confirms the condition with fifteen failures among twenty samples at 100 ms intervals. The high branch does not use the paired low readings printed for P0B74, and it does not use the scaled pack-voltage comparison printed for P0B73.

Those distinctions matter when several related codes are present. Preserve their status and associated data instead of collapsing them into a single assumption that the battery is overcharged or that one block must be replaced.

Establish the measurement context

The documented test requires RUN mode, a low-voltage supply between 9 and 18 V and P0A1F inactive. These are eligibility conditions for the controller's decision. They do not specify what voltage a technician should apply to the high-voltage sensing circuit.

Review the block 12 trace alongside other relevant measurements under an eligible operating state. The source leaves the physical cause unresolved, so repair selection needs the correct hybrid diagnostic procedure. A warning that disappears after memory clearing is less persuasive than documented normal readings and a completed, eligible monitor.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, cited BPCM or hybrid-controller monitor only. Historical calibration values are not universal specifications; no per-code model, engine or hardware fitment has been established. GM PDF, physical page 228.