P0B72: Battery voltage sense L has excessive calculated resistance

P0B72 concerns hybrid/EV battery voltage sense circuit L. The 2018 GM table describes a high-resistance or open sense-line monitor, rather than a simple comparison of a cell's resting voltage with a low-voltage limit.

The controller creates a measurement opportunity

After a normal cell-voltage reading, the controller operates balancing gates in a test pattern. Current through a sense wire produces a voltage drop; the monitor uses that change to calculate resistance. More than 30 ohms is the documented failure threshold, with seven failures out of nine samples taken 100 milliseconds apart.

GM explains that high sense-wire resistance affects both voltage measurement and charge balancing. Therefore, an abnormal reported cell voltage can involve the measurement path rather than establish loss of cell capacity. The source requires system voltage above 10.2 V and no battery interface control-module communication fault from the specified group. Reporting is Type A, one trip.

What helps distinguish the fault

Preserve sense-circuit L identity, communication status and any available balancing-test result. A reassuring static cell-voltage snapshot does not recreate the current-dependent test. Conversely, this DTC is not proof that a battery cell itself must be replaced.

Use the vehicle-specific pack schematic to identify circuit L; the letter does not provide a universal physical cell number or accessible connector. Internal sense wiring and balancing components require qualified high-voltage service. Verification must address the monitored resistance response and the manufacturer's pack checks, without manually reproducing the balancing test.

Source and applicability

This explanation follows the documented GM monitor, not a verified application to every vehicle with this code. Confirm the vehicle, reporting module and calibration in current service information. GM diagnostic table, physical page 832.