Powertrain, generic · Hybrid propulsion

P0B81 Hybrid/EV Battery Voltage Sense O Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B81 stands for an open sense lead on channel O, the fifteenth cell tap. GM has used it from the start: the 2011 Volt battery tables already list P0B81 among the open sense line codes and detect, among other cases, a busbar connection voltage above 0.7 V. In the 2019 battery energy control module the test needs 0.8 s within a 1.6 s window, with adjacent cells 1.3 V or more apart or a balancing gate below 36 mV, Type A. The BAS Plus mild hybrid compares lines N and N-1, both under 1.4 V with a change above 0.5 V in 200 ms, 7 of 10 samples, Type B. Unlike channels M and N, P0B81 does not appear in Ford's Fusion plug-in bulletin. With the lead open, the controller loses sight of that cell and limits operation.

Likely causes

Loose or high-resistance busbar joint at the O tap
Broken sense wire O in the battery harness
Faulty cell sense module

Symptoms

  • MIL and propulsion system warning
  • Reduced power or no electric drive

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–6,500
Time1–10 h

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

Parts involved

hv battery voltage sense owiring harnessbms

Related codes

P0B82P0B83P0B84P0B85P0B7CP0B86

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