Powertrain, generic · Hybrid propulsion

P0B56 Hybrid/EV Battery Voltage Sense F Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

The GM two-mode hybrids of 2012, Tahoe, Yukon, Escalade, Silverado and Sierra, show a detail of P0B56 that lithium-ion packs lack. Their nickel-metal hydride pack is read in blocks, channel F being block 6, and the battery pack control module sets the code only when block 6 and block 7 both read under 2 V in 15 of 20 samples at 100 ms, Type B, two trips; a shared sense wire between the blocks is the obvious suspect then. In GM's lithium-ion systems the battery energy control module uses 0.2 V or less on cell voltage F for 1.4 s within 2 s, Type A. In both cases the controller assumes a failed measurement and reduces battery use until repair.

Likely causes

Fault in the sense wire shared by blocks 6 and 7 (GM two-mode)
Channel F sense line shorted to a neighbouring line
Failed input on the cell monitoring electronics

Symptoms

  • Hybrid system warning, MIL after the second drive (two-mode)
  • Engine runs continuously, no electric launch
  • Lower fuel economy

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 fwiring harnessbms

Related codes

P0B54P0B55P0B57P0B58P0B51P0B5B

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