Powertrain, generic (extended)

P2BC8 Battery Charging System Positive Contactor B Control Circuit Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2BC8 flags a control circuit of positive charging contactor B that is connected but behaves implausibly: the coil draws a current that does not fit the command, the line voltage lies in an unexpected band, or pulling in takes too long. No manufacturer documents P2BC8 publicly. CARB demands rationality checks in addition to circuit checks for the charging components of plug-in vehicles. A GM patent explains one way to judge a coil: send a short pulse, record the current response and compare it with stored values, which reveals a winding or armature that no longer behaves as designed. Likely culprits are corrosion at the pins, a coil with drifting resistance and an ageing output stage. Opens are P2BC7, hard low or high readings P2BC9/P2BCA, the contactor A equivalent P0D0B. Charging may work only intermittently.

Likely causes

Contact resistance at connectors of the control line
Coil resistance of contactor B outside specification
Driver stage in the module degraded

Symptoms

  • Charging works only now and then
  • Charging aborts with a 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

P2BC7P2BC9P2BCAP2BCFP0D0B

References: law.cornell.edu, patents.google.com.