Powertrain, generic (extended)

P2BC4 Battery Charging System Positive Contactor B Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2BC4 is the catch-all electrical code for positive contactor B of the charging system, the second charging switch on the plus side next to contactor A (P0D07). Which charging path B serves is up to the maker: Mercedes-Benz files its B codes under the DC charge connection unit of its plug-in hybrids, EQB and eSprinter, Mazda under the on-board charger branch of its two large plug-in SUVs, and Audi calls it charging contactor 2 on the Q8 e-tron. No manufacturer documents P2BC4 itself publicly. Under CARB the charging system of plug-in vehicles has to be supervised, and a GM patent judges such contactors by their coil current. Fused or non-closing contacts are P2BC5/P2BC6, driver faults P2BC7–P2BCA, the minus side P2BCB. Usually only the affected charging mode is lost.

Likely causes

Coil of positive contactor B open or shorted
Wiring or connector fault in the contactor B branch
Fault or software issue in the controlling module

Symptoms

  • DC fast charging or on-board charger charging (depending on design) refused
  • Charging fault message in the cluster or app
  • Driving usually still possible

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–1,800
Time1–6 h

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

Parts involved

bcs pos contactor bwiring harnessbms

Related codes

P2BC5P2BC6P2BC7P2BCBP0D07

References: law.cornell.edu, patents.google.com, static.nhtsa.gov, static.nhtsa.gov.