Powertrain, generic · Hybrid propulsion

P0B7A Hybrid/EV Battery Voltage Sense M Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

A reading on channel M above what any healthy cell can deliver produces P0B7A. For lithium-ion packs GM sets the line at 4.8 V or more for 1.4 s in a 2 s window and treats it as Type A, illuminating the MIL on the first trip. The BAS Plus mild hybrid already reacts above 4.65 V in 7 of 10 samples, Type B. Where M stands for NiMH block 13, as on the 2012 two-mode trucks, a block voltage above 23 V for 15 of 20 samples is the trigger, again Type B, with the 12 V system between 9 and 18 V. Because a cell itself rarely climbs that high, a sense lead touching a higher potential or a faulty measuring input is far more likely than overcharging. The vehicle will usually limit charging and electric drive.

Likely causes

Sense lead M in contact with a higher cell potential
Measuring input of channel M reading high
Real overvoltage of the cell after a balancing fault

Symptoms

  • MIL on from the first trip (GM lithium-ion, Type A)
  • Charging stopped or limited
  • Reduced electric 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 mwiring harnessbms

Related codes

P0B77P0B78P0B79P0B7BP0B75P0B7F

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