Powertrain, generic (extended)

P2BC6 Battery Charging System Positive Contactor B Stuck Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2BC6 means positive charging contactor B does not close when commanded, so the plus side of that charging branch stays dead and the session aborts or never starts. The only maker documenting it publicly is Mazda: on the 2024–2026 CX-90 and 2025–2026 CX-70 plug-in hybrids it reads OBC contactor (+) stuck off, listed with the welded cases P2BC5 and P2BCC. Mazda traces all three to a contact-welding problem in these contactors and fits a new Junction Box No. 2 (bulletin 30-003-26). GM's analogous test for contactor A on the Chevrolet Volt (P0D09) shows the principle: during precharge the voltage on the charger side must build up, and a reading under 10 V ends the check as failed. Welding is P2BC5, the negative side P2BCD. Driving normally continues.

Likely causes

Contactor B damaged inside and no longer closing (Mazda junction box)
Coil supply or drive line interrupted
Charging control software misjudging the closing check

Symptoms

  • Charging session stops or does not start
  • Hybrid system malfunction message (Mazda)
  • Driving usually unaffected

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 pos contactor bwiring harnessbms

Related codes

P2BC4P2BC5P2BC7P2BCDP0D09

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