B3791

Code

Generic B — Body

Body Control Module (BCM) Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 19 EN: 14 RU: 13

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Page language: EN

VBAT and ignition feed voltage at BCM (should be stable at battery/ignition levels)
Ground integrity — voltage drop to chassis ground under load (millivolts)
CAN_H and CAN_L idle voltages (approximately mid-supply ~2.5 V each) and differential during activity
CAN bus error/frame rate and presence of repeated error frames
LIN or local bus wake/poll signals as applicable to vehicle
BCM supply current (check for abnormal quiescent drain)

Read and record all DTCs and freeze-frame data from the BCM and other modules. Note time-stamps and ignition state.
Verify battery voltage and charging system. Ensure a fully charged stable battery before further tests or reflashing.
Visually inspect BCM and harness connectors for water, corrosion, bent pins, or heat damage. Repair or reseat as needed.
Check fuses/relays feeding the BCM and measure supply and ground at the module connector while operating affected circuits.
Confirm network communication with a scan tool. If communication is lost, check bus termination resistances and for shorted CAN lines.
Attempt to clear codes and reproduce fault. If DTC returns, capture live data and bus traffic (use oscilloscope if available) to identify anomalies.
If software-related, check for available service updates and attempt a reflash/reprogram following manufacturer procedure with stable power.
If internal hardware fault is suspected after verification of power, grounds and wiring, consider module bench test or replacement. Follow manufacturer pairing/coding/immobilizer re-learning procedures when installing a replacement.
After repair or replacement, verify all related systems and clear codes, then road-test to confirm fault does not return.
If intermittent or unclear, document conditions and consult manufacturer support or TSBs before replacing module.