B100A

Code

LAND ROVER B — Body

Body Control Module Internal Fault

Brand: LAND ROVER

Type: B — Body

Views: UK: 21 EN: 39 RU: 38

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Page language: EN

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

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