Powertrain, generic (extended)

P2BC9 Battery Charging System Positive Contactor B Control Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2BC9 is the low-signal fault on the coil feed of plus-side charging contactor B: the module measures less voltage on that wire than its command calls for, most often because the wire touches ground or the output stage is being dragged down. With a high-side feed the coil is then starved and the contactor never pulls in, or the output stage trips its own protection. No manufacturer documents P2BC9 publicly. GM notes for its corresponding contactor A test on the Chevrolet Volt (P0D0A) that the open-circuit check cannot detect a short to ground, so this case needs a check of its own. CARB requires monitoring of the charging system on plug-in vehicles. Expect insulation rubbed through on the battery casing or moisture inside a plug. P2BCA is the high counterpart, P2BD0 the same fault on the minus side. That charging mode is then refused.

Likely causes

Control wire of contactor B shorted to ground
Moisture or corrosion in a connector
Coil of contactor B internally shorted

Symptoms

  • Charging session does not start
  • Charging fault message

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–1,500
Time1–5 h

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

Parts involved

bcs pos contactor bwiring harnessbms

Related codes

P2BC7P2BC8P2BCAP2BD0P0D0C

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