Powertrain, generic (extended)

P2BCC Battery Charging System Negative Contactor B Stuck Closed

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

P2BCC says negative charging contactor B is still closed although the module ordered it open – in practice fused contacts on the return side. Mercedes-Benz lists it in the DC charge connection unit next to P2BC5 and P0E8929 (DC input current too high); the plug-in hybrid, EQB or eSprinter then cannot be started after DC charging. The bulletins name ripple and overvoltage from the station and contacts that open too late, and call for a software update and a contactor-fault reset instead of a new unit. Mazda names it OBC contactor (−) stuck on in the same bulletin and also prescribes a new Junction Box No. 2. Hyundai and Toyota patents find such welding by opening one pole while the other stays closed and checking the voltage behind it. P2BC5 is the plus side, P2BCD the reverse fault.

Likely causes

Contacts of negative contactor B welded at the end of charging
Charging module software (Mercedes update)
Current ripple or overvoltage from the DC station

Symptoms

  • Vehicle will not start after DC charging (Mercedes)
  • High-voltage system warning
  • Charging blocked

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–4,000
Time0–10 h

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

Parts involved

bcs neg contactor bwiring harnessbms

Related codes

P2BCBP2BCDP2BC5P0E89P0D0F

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, patents.google.com.