B2670

Code

Generic B — Body

Body Control Module (BCM) Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 13 EN: 27 RU: 17

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Page language: EN

Multiple unrelated body functions inoperative or intermittent (lights, locks, wipers, etc.)
Illuminated warning lights related to body or communication faults
Loss of communication with BCM on diagnostic tool (U codes may be present)
Modules entering limp behavior or default modes
Intermittent operation that may resolve temporarily after battery disconnect or key cycle

Read all stored DTCs (including U and B codes) with a capable scan tool and note freeze frame/data
Check battery voltage with key off and during crank; ensure >=12.4V at rest and >=9.6V during cranking
Visually inspect BCM connectors and wiring for corrosion, damage, or water intrusion
Inspect BCM mounting area for signs of moisture or impact
Check main power and ground pins at BCM for good continuity and low resistance
Scan CAN/LIN network for communication faults and other module faults

Battery supply at BCM: nominal ~12V (12.4–12.8V at rest, 13.5–14.8V charging)
Ignition-switched feed: stable when ignition ON, no brownouts during operation
Ground resistance: typically
CAN bus differential idle: ~2.5V on CAN_H and CAN_L (approx. 2.5V each, 2.5V ±0.5V typical), differential ~0V idle voltages around 0V but measured with scope as ~2.5V/1.5V split
LIN bus idle: near supply voltage when idle (checks per vehicle spec)
Watchdog resets/errors logged in BCM event memory

Retrieve all codes from BCM and other modules; record freeze-frame and any U-codes indicating network loss.
Verify battery state-of-charge and charging system; charge or replace battery if voltage low or unstable.
With key off, disconnect BCM connector(s) and inspect pins for corrosion, bent pins, or water damage; repair as needed.
Check power and ground pins for continuity to battery and chassis ground; measure voltage at BCM connector with key ON and cranking.
Check CAN/LIN communication with an oscilloscope or advanced scan tool: confirm bus activity and correct voltage levels; isolate any bus short to ground or battery.
Clear codes and reproduce symptom; monitor for reappearance and note conditions when fault sets (temp, key state, events).
If power/ground and network are good, verify BCM software/calibration against manufacturer spec and reflash/update if newer/recommended file available.
If reflashing fails or fault persists after correct power, ground, and network verification, consider BCM replacement; follow module programming and security procedures when replacing.
After repair or replacement, reprogram and reinitialize BCM per vehicle procedures, clear codes, and verify all related systems operate correctly.