Powertrain, generic · Hybrid propulsion

P0B91 Hybrid/EV Battery Voltage Sense R Circuit Range/Performance

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

Here the wiring of sense R is intact, but its value does not behave like a real cell. GM's 2019 hybrid powertrain processor demands that cell R moves at least 0.005 V in the same direction whenever the cell average shifts by more than 0.022 V; 35 failures out of 40 samples at 100 ms give a Type A fault. The 2016 Volt allows 7 s of failure in an 8 s window, the ELR 20 of 40 samples at 200 ms. On the 2012 two-mode trucks R is nickel-metal hydride block 18: blocks 18 and 19 are each multiplied by twenty, and if both estimates miss the pack voltage by more than 70 V in 160 of 170 samples, P0B91 is set as Type B. A frozen measuring channel or controller software is the usual suspect.

Likely causes

Measuring channel R reporting a stuck value

Outdated battery controller or hybrid processor software

Block 18 or 19 voltage drifting on two-mode NiMH packs

Symptoms

MIL on, vehicle often drives normally
Less electric assist or regenerative braking

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€80–5,000

Time0.5–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery voltage sense rwiring harnessbms

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.