B3150

Code

Generic B — Body

Body Control Module Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 8 RU: 5

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Page language: EN

Multiple body systems inoperative or intermittent (locks, lights, windows, wipers)
BCM-related warning lamp on dash or message center alert
Loss of communication with BCM on a scan tool
Vehicle functions reset or behave erratically after key cycles
Stored multiple B- or U- codes related to BCM and bus communication

Use a scan tool to read all stored codes, freeze frame and freeze-frame conditions; note repetition and history
Verify battery voltage at rest and during cranking (should be ~12.0–14.5 V)
Inspect BCM connectors, pins and harness for corrosion, water, bent pins or damage
Check BCM ground(s) for corrosion, tightness and low resistance to chassis
Verify proper fuses and relays feeding the BCM are intact and seated
Check CAN/LIN network for communication with other modules using a scan tool

Battery supply to BCM: ~12.0–14.5 V during operation (stable, not intermittent)
Ignition-switched supply present when key ON (per vehicle spec)
CAN bus idle voltage: ~2.5 V on CAN_H and CAN_L (differential idle ~0 V); dominant states ~3.5 V/1.5 V respectively
LIN bus idle: typically near battery or ground reference per vehicle spec; check waveforms for wake/sleep
Wake/sleep line(s) logic states as defined by vehicle (verify with service data)
Ground continuity: low ohms to chassis (

Record code(s), freeze frame and vehicle history with a capable scan tool; note repeatability and related modules affected.
Confirm stable vehicle battery voltage and charging system health; charge battery if low and re-check.
Visually inspect BCM and harness for water intrusion, corrosion, physical damage and connector pin condition; repair any damage.
Verify all BCM power feeds and ground circuits for proper voltage and low resistance; wiggle-test harness while monitoring for changes.
Check network communication: attempt to communicate with BCM and other modules on CAN/LIN. If BCM is not responding but bus active, test transceiver lines for proper voltages and termination.
Clear codes and operate affected systems; see if fault returns and under what conditions. Capture freeze-frame when it reappears.
If intermittent or software-related, check for available reflash/calibration updates or known TSBs; perform software reflash per OEM procedure.
If module fails bench voltage/power or communication tests, compare to known-good specifications; consider connecting a known-good BCM (if available and programmable) to confirm behavior.
If replacement BCM is required: obtain correct part, program/calibrate to vehicle and immobilizer/security systems per OEM procedures. Re-learn functions and re-check all body systems.
After repair, road-test and re-scan to confirm no recurrence and proper communication across networks.