Powertrain, generic · Hybrid propulsion

P0B7B Hybrid/EV Battery Voltage Sense M Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B7B is reserved for a sense M signal that flickers: short dropouts or jumps while the circuit is otherwise intact. No manufacturer documents this code publicly. GM's tables for channel M contain open, plausibility, low and high tests but no erratic test, and Ford's Fusion bulletin lists only the open-circuit code P0B77. The legal footing is CARB 1968.2, which requires the battery voltage sensors of a hybrid energy storage system to be monitored as electronic components and demands fault codes that point to the smallest replaceable unit. In practice a loose crimp at the M tap, a chafed lead in the sense harness or a cracked solder joint on the monitoring board would cause such a signal. Expect warnings that come and go.

Likely causes

Loose crimp or connector at the channel M tap
Chafed wire in the cell sense harness
Cracked solder joint on the monitoring board

Symptoms

  • Hybrid warning appearing and clearing again
  • Brief drops in electric power

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–5,000
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

P0B77P0B78P0B79P0B7AP0B76P0B80

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov.