P2BC6

Code

Generic P — Powertrain

Battery Charging System Positive Contactor B Stuck Open

Brand: Generic

Type: P — Powertrain

Views: UK: 19 EN: 37 RU: 24

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Contactor B mechanical failure (contacts welded or stuck open)
Contactor B coil or internal driver open or shorted
Control module (BCM/PCM) driver transistor or MOSFET failure
Open or shorted wiring between control module and contactor (harness, connector fault)
Blown fuse or fusible link in contactor control or supply circuit
Battery voltage extremely low preventing contactor operation

Charging system warning lamp or message illuminated
Battery not charging or slow charging / reduced charging current
Vehicle may run on battery only or enter limp mode
Intermittent loss of battery positive supply to certain loads
Low system voltage or repeated jump-start events
Possible no-crank or accessory power loss if contactor is part of main battery feed

Check battery state-of-charge and resting voltage (12.4–12.8 V nominal; >12.2 V preferred for tests)
Visually inspect contactor and wiring for corrosion, heat damage, loose terminals or melted insulation
Check relevant fuses and fusible links for continuity
Scan for additional DTCs that indicate driver or supply faults (voltage, communication)
Back-probe contactor coil/control connector while commanding contactor closed from scan tool (if allowed)
Measure voltage at contactor supply terminal and coil/control terminal during commanded closure

Battery supply to contactor (unswitched/switchable): ~12 V nominal with battery charged
Control/coil command voltage (when commanded CLOSED): ~12 V (or driver ground/low depending on design). When commanded OPEN: ~0 V (or no coil supply) — consult OEM polarity
Coil resistance: typically low (single-digit ohms to tens of ohms) — check OEM spec; open (infinite) indicates broken coil
Voltage drop across main contact when closed: small (
Module command status (controller output) should change state when commanded by scan tool — verify logical HIGH/LOW or PWM per OEM

Record freeze frame and all related DTCs. Confirm battery voltage and state-of-charge; charge battery if low and retest.
Visually inspect contactor, mounting, connectors, wiring harness and fuses for damage, corrosion or overheating. Repair obvious issues.
Using a scan tool, command Contactor B closed while monitoring coil/control terminal and supply terminal at the contactor. Verify the module issues a command and measure resulting voltages.
If module commands but coil has no supply voltage, check fuses/fusible links and the supply circuit to the contactor. Repair open circuits.
If coil has supply when commanded but contactor does not close, measure coil resistance and verify mechanical movement. Replace contactor if coil open, shorted, or mechanically stuck.
If coil does not get a command from the module, diagnose the driver output circuit at the module (look for blown internal FET/transistor) and inspect communications/power to module. Follow OEM diagnostics before replacing module.
After repair, clear codes and perform functional test under load and driving conditions to confirm contactor closes reliably and no reoccurrence of P2BC6.
If intermittent, perform wiggle tests and endurance cycling while monitoring to reproduce the fault; consider harness replacement or contactor replacement if intermittent connection is found.