Powertrain, generic · Hybrid propulsion

P0B51 Hybrid/EV Battery Voltage Sense E Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B51 tells that cell sense channel E reads near zero. GM's battery energy control module only runs this check under clear conditions: the module is in run, crank or accessory mode, the second protection self-test is not running, and no slave communication, open sense line, balancing or internal performance fault is active. Then a reading of 0.2 V or less for 1.4 s in a 2 s window sets the code, Type A, one trip. The order matters for diagnosis: an open sense line or a lost slave board would be reported first by their own codes. On the 2012 two-mode hybrids channel E is block 5, set when blocks 5 and 6 both drop below 2 V, Type B. Electric operation is then restricted.

Likely causes

Channel E sense line shorted to its neighbour
Faulty input on the cell monitoring slave board
Pin backed out of the monitoring harness connector

Symptoms

  • MIL and hybrid system warning
  • Electric-only driving unavailable

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–5,000
Time0.3–6 h

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

Parts involved

hv battery voltage sense ewiring harnessbms

Related codes

P0B4FP0B50P0B52P0B53P0B4CP0B56

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