P0B64: block 9 performance cannot be judged from one voltage alone

P0B64 is the rationality branch of block 9 voltage monitoring in the cited GM source. A scanner may expand it as voltage-sense circuit I range/performance. In this application, the important issue is whether the block measurements agree with a separate pack-voltage measurement.

The paired plausibility test

GM specifies an absolute difference greater than 70 V between twenty times block 9 voltage and pack voltage. The equivalent calculation for block 10 must also exceed 70 V. Both comparisons are required by the row; the code should not be reduced to a single-channel low-voltage alarm.

The controller needs 160 failing samples out of 170, with a 100 ms interval. That counter helps distinguish persistent disagreement from an isolated update or transient. It is not a published instruction to apply a particular load to the battery for a fixed duration.

Confirm that the inputs were eligible

The block 9 signal must be valid, the BPCM must be in RUN, and the contactors must have been closed for more than 200 ms. Listed block and pack sensing faults inhibit this check. Their presence matters before interpreting a later absence of P0B64 as repair confirmation.

Keep the block 9, block 10 and total-pack values together when discussing the diagnosis. The source describes a consistency test, not a verdict on which component is defective. Vehicle-specific procedures and high-voltage training are required for physical investigation.

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 227.