Code
B100A
LAND ROVER
B — Body
Body Control Module Internal Fault
Views:
UK: 6
EN: 12
RU: 5
AI status
Completed
Completed
100%
Causes
- BCM internal hardware failure (processor, memory, internal power regulation)
- Corrupted or failed BCM firmware/software
- Intermittent or low supply voltage / poor ground at BCM
- Water intrusion or corrosion at BCM housing or connectors
- Voltage transients or a jump-start event that damaged internal electronics
- Aftermarket alarm/immobilizer or poor-quality modification interfering with BCM
Symptoms
- One or more body systems inoperative or intermittent (locks, lighting, wipers, interior functions)
- Warning lamp or message on dash related to vehicle electronics or BCM
- Loss or intermittent loss of communication with BCM on diagnostic scanner
- Erratic operation of central locking, alarm, or convenience features
- Parasitic battery drain or unexpected battery flat when parked
- Multiple unrelated DTCs present in other modules (communication errors)
What to check
- Scan vehicle with a factory-level or manufacturer-capable diagnostic tool; record all stored and pending DTCs and freeze frame data
- Confirm battery resting voltage and charging system voltage (battery >= 12.2 V; while running ≈ 13.5–14.8 V)
- Visually inspect BCM connectors and harness for corrosion, damage, water ingress, or loose pins
- Check BCM main fuses, relays, and fusible links feeding the module
- Verify good chassis and engine grounds associated with BCM
- Check for aftermarket alarms, trackers or remote-start systems and disconnect them for testing
Signal parameters
- Battery voltage at BCM connector: typical resting ≈ 12.2–12.8 V; charging (engine running) ≈ 13.5–14.8 V
- Cranking voltage: should not drop below ~9.5–10.5 V under normal starter load (vehicle-specific)
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); dominant states typically produce ~3.5 V / ~1.5 V respectively
- CAN differential signal when active: typically around 2 V differential during dominant bits
- Parasitic current draw: expected values vary by model; unexpected high draw (>100 mA) warrants investigation
- Module wake/sleep current and wake-message presence as reported by manufacturer scan data
Diagnostic algorithm
- Use a manufacturer-capable diagnostic tool to read and log all BCM and network DTCs, freeze frame and live data. Note related U-codes from other modules.
- Verify battery state of charge and charging system. Recharge battery if needed and retest — low battery can cause module faults.
- Inspect BCM physical condition and harness: look for water entry, corrosion, bent/missing pins, rodent damage, or signs of overheating.
- Check and measure power and ground at the BCM connector with connector connected: main +12 V feed(s), switched feeds, permanent feed, and ground continuity to chassis.
- Verify CAN/LIN bus continuity and resistance (terminations) and check voltage levels with key on. Repair any short/open or incorrect termination.
- If external power/ground and network are good, clear DTCs and power-cycle vehicle. If B100A returns immediately or intermittently, suspect internal BCM fault.
- Check for and remove aftermarket devices; repeat tests. Perform wiggle tests on harness while monitoring communication for intermittent faults.
- Verify BCM software/calibration level against factory specifications; perform reflash/update if a newer, validated calibration is available.
- If reflash does not clear the fault and all external causes are eliminated, follow manufacturer procedure for BCM replacement, ensuring module coding/immobilizer programming and security pairing are performed as required.
- After repair or replacement, re-scan all modules, confirm proper communication, clear codes and verify all related systems function normally. Document procedures and parts.
Likely causes
- Internal BCM hardware failure or corrupted firmware (most likely if fault persists across power cycles and other modules show communication issues)
- Poor battery/charging supply or poor ground at BCM (common and must be eliminated early)
- Water ingress / connector corrosion (likely if vehicle has been exposed to moisture or front/rear modules affected)
- Aftermarket electrical additions or incorrect repairs creating noise or backfeed on networks
- Transient event (voltage spike) that corrupted BCM software
Fault status
Status
Internal Body Control Module fault detected. Module may be malfunctioning or reporting internal hardware/software errors. Further electrical and diagnostic testing required to isolate internal failure vs external cause.
Repair difficulty: Hard
Diagnostic time: 1.5 - 3.5 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop Manual199,00 UAH
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop Manual199,00 UAH
Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop Manual199,00 UAH
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