Powertrain, generic · Hybrid propulsion

P0B66 Hybrid/EV Battery Voltage Sense I Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

When channel I claims a voltage above what its cell or block can physically reach, the controller stores P0B66. The thresholds GM publishes depend on chemistry and architecture: lithium-ion packs with a battery energy control module set it at 4.8 V or more for 1.4 s in a 2 s window, Type A, one trip; the BAS Plus mild hybrid at above 4.65 V in 7 of 10 samples, Type B; the 2012 two-mode trucks, which measure nickel-metal hydride block 9 rather than single cells, above 23 V in 15 of 20 samples, Type B. Every limit sits clearly above normal full charge, so a real overcharged cell is unlikely. Look first for a sense lead touching the next tap up or for a measuring input that has lost its reference.

Likely causes

Channel I lead touching a higher-potential tap
Open reference or ground of the measuring chip
Genuinely overcharged cell after a charging control fault

Symptoms

  • Charging stops or is refused
  • MIL and reduced power

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 iwiring harnessbms

Related codes

P0B63P0B64P0B65P0B67P0B61P0B6B

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.