B0845

Code

Generic B — Body

Body Control Module Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 15 EN: 14 RU: 15

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Page language: EN

Causes

BCM internal hardware failure (CPU, memory, or internal power regulator)
Corrupted or failed BCM firmware/software
Intermittent or incorrect BCM supply voltage or ground
CAN/LIN bus electrical issues causing module errors
Water ingress, corrosion, or physical damage to the BCM housing or connector
Aftermarket electrical work or jump-start damage

Symptoms

Instrument cluster warnings or lamp indicating BCM fault
Multiple unrelated electrical functions operating incorrectly (lighting, locks, wipers, etc.)
Intermittent or permanent loss of functions controlled by BCM
Stored DTC B0845 in BCM freeze frame and freeze data available
Communication loss with BCM on diagnostic tool or restricted data availability

What to check

Inspect BCM connector for corrosion, bent pins, or water intrusion
Verify battery voltage with key off and key on (should be ~12.0–12.6 V off, ~13.5–14.5 V while running)
Check BCM ground integrity and continuity to vehicle chassis
Scan for other related DTCs (BCM and communication bus codes) and read freeze frame data
Visual inspection of BCM housing for physical damage or signs of repair or overheating

Signal parameters

Battery supply (VBATT) at BCM: ~11.5–14.8 V depending on state
Ground continuity: near 0 Ω to chassis ground
CAN bus idle voltages: CAN_H ~2.5 V, CAN_L ~2.5 V (differential ~0 V) when idle; normal dominant levels when active
LIN bus idle: ~12 V pulled to wake/sleep levels as specified by vehicle
Module responds to diagnostic poll (ISO 14229/UDS) or reports communication timeout/failures

Diagnostic algorithm

Record full DTC list and freeze frame data from BCM and gateway modules
Verify battery state of charge and charging system health; ensure stable supply voltage during diagnosis
Perform a visual and physical inspection of BCM connector, pins, and PCB (if accessible) for moisture, corrosion, or damage
Check power and ground circuits: measure VBATT at BCM connector and verify good ground continuity to chassis
Scan vehicle network for communication errors (bus-off, timeouts) and look for related U-codes; disconnect non-essential modules if needed to isolate bus problem
If wiring and power/ground are good, attempt to re-flash or update BCM software using correct OEM procedure and verified package
If re-flash fails or software update does not clear internal fault, consider module replacement; program and configure new BCM per manufacturer procedure
After repair, clear DTCs and perform a full functional check of BCM-controlled systems and monitor for reoccurrence

Likely causes

Failed BCM internal power regulator or voltage spikes
Corrupted module software or failed software update/flash
Intermittent main power or ground to BCM (loose connector, damaged wiring)
CAN/LIN transceiver failure inside BCM
Moisture or corrosion on BCM PCB or connector pins

Fault status

⚠️ Status

Stored code B0845 — BCM internal fault. Indicates module self-test or internal diagnostics detected hardware/firmware/memory failure; verify power/ground, communication bus, and perform software reflash or module replacement as required.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.0-3.0 hours