B0407

Code

Generic B — Body

BCM Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 6 EN: 11 RU: 8

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Malfunction or loss of body systems (door locks, interior lighting, wipers, windows, HVAC blend doors, etc.)
Multiple body-related warning lights or alerts
Intermittent operation of several unrelated body functions
Communication errors with scan tool (lost or intermittent responses from BCM)
Stored B0407 with possible companion codes for power, ground, or CAN/U‑codes
Vehicle entering reduced/function-limited mode for body systems

Read all stored codes and freeze frame data with a capable scan tool; record related U‑ and B‑codes
Check battery state-of-charge and charging system voltage (engine running ~13.5–14.5 V)
Visually inspect BCM and connectors for water, corrosion, heat damage, or bent pins
Verify fuses and relays associated with BCM power and key circuits
Check and measure BCM supply voltage and ground at the module connector
Inspect CAN/LIN wiring and connectors; check for proper termination and short to battery/ground

Module supply voltage (nominal ~12 V; check during cranking and while running)
Battery voltage and cranking voltage (should not drop excessively during cranking)
Module ground resistance to chassis (low ohms;
CAN_H and CAN_L differential voltage (idle ~2.5 V each; differential ~0 V idle with frames visible)
Presence of valid CAN frames and data traffic on the bus (packets/sec, no continuous errors)
LIN bus voltage levels and signal pulses if BCM uses LIN subnets

Retrieve complete DTC list, freeze frame data and any history. Note time and conditions when B0407 set.
Check battery condition and charging system. Recharge or replace battery if voltages are low or unstable.
Visually inspect BCM location, mounting, connectors and wiring for moisture, corrosion, damage or rodent issues.
Verify fuses and relays powering the BCM. Replace any blown fuses and test related relays.
With key on, measure supply voltage and ground at the BCM connector pins. Repair any faults in power/ground circuits.
Inspect and test CAN/LIN communication lines: check continuity, short to voltage/ground, and CAN termination (approx. 120 Ω). Use oscilloscope or capable scan tool to verify valid bus traffic.
Attempt to communicate with BCM using OEM scan tool. If no communication or intermittent, try another known-good diagnostic interface and recheck wiring.
If electrical supply and communications are normal, check BCM software level. Compare against OEM release and apply any recommended updates or reflash procedures.
If software reflash fails or errors persist and bench testing shows internal faults, follow OEM procedure for BCM replacement. Program/initialize new replacement BCM per manufacturer requirements.
After repair, clear codes and perform full functional test of all affected body systems and confirm the code does not return. Record final results and any replaced parts.