Powertrain, generic · Hybrid propulsion

P0B8E Hybrid/EV Battery Voltage Sense Q Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Channel Q reporting an implausibly high voltage sets P0B8E. On the 2012 GM two-mode hybrids, where Q is NiMH block 17, the limit is 23 V for 15 of 20 samples, Type B, checked only while the 12 V system lies between 9 and 18 V. GM's lithium-ion programs work at cell level: 4.8 V or more for 1.4 s in 2 s in the 2016 and 2019 battery controllers, more than 4.90 V in 14 of 18 samples where a separate battery sense module measures, all Type A. The BAS Plus mild hybrid limit is 4.65 V. As with the other high codes of this family, wiring and measuring input are far more often to blame than the cell; a damaged harness that lets lead Q touch the next tap is a classic finding. Charging and regeneration are limited.

Likely causes

Damaged harness letting lead Q touch the next tap
Measuring input of channel Q reading high
Real cell overvoltage after a balancing failure

Symptoms

  • Regeneration and charging limited
  • MIL and battery system warning

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–6,000
Time1–8 h

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

Parts involved

hv battery voltage sense qwiring harnessbms

Related codes

P0B8BP0B8CP0B8DP0B8FP0B89P0B93

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