B0740

Code

Generic B — Body

Body Control Module — Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 10 EN: 8 RU: 9

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Page language: EN

Multiple body electrical features fail or behave intermittently (locks, lights, wipers, interior lighting)
Instrument cluster or other modules report BCM communication loss
Illuminated general warning light or BCM-related lamp
Modules fail to wake or sleep properly; keyless entry or remote functions fail
Stored communication errors (U-codes) together with B0740

Retrieve stored codes and freeze frame data with a capable scan tool; note history and conditions
Check overall network: verify other modules can communicate with scan tool (CAN/LIN status)
Measure and verify battery voltage with engine off and cranking; check charging system voltage with engine running
Inspect BCM connector(s) for corrosion, bent pins, or water intrusion; verify harness condition and routing
Check fuses and fusible links feeding BCM power and ignition circuits
Visually inspect BCM for physical or moisture damage (do this with vehicle battery disconnected if you will remove module)

Battery voltage (key ON): nominal 12.0–13.5 V; while running 13.5–14.8 V
Cranking voltage: not less than ~9.6–10.5 V (depending on vehicle)
CAN bus idle voltages: CAN_H ≈ 2.5–3.0 V, CAN_L ≈ 1.5–2.5 V; differential ~0 V recessive, dominant CAN_H ≈ 3.5 V and CAN_L ≈ 1.5 V
LIN idle: pulled to battery voltage (approx. 12 V) when recessive; dominant pulls low (~0–2 V)
Ground resistance: BCM ground to chassis should be low (

Connect a diagnostic scanner and record B0740 and any related codes (U-codes, other B-codes). Save freeze frame and occurrence data.
Verify battery condition and charging system. Repair weak battery or charging faults, then clear codes and retest.
Check BCM power and ground circuits: inspect fuses, fusible links, relay outputs, and measure pin voltages at BCM connector with key ON/engine as required.
Inspect physical condition of BCM and connector for corrosion, water ingress, bent pins, or burnt smells. Repair wiring or connector faults found.
Verify vehicle network communications: check CAN/LIN voltages and message presence using scope/scan tool. Repair bus wiring or terminators if abnormal.
If external power, ground, and communications are normal, attempt to reinitialize or reflash BCM software per manufacturer procedure; check for available software updates/TSBs.
If reflashing fails or module reports internal hardware faults after software attempts, consider replacing BCM. Ensure replacement module is the correct part and perform any required programming, VIN/immobilizer pairing, and configuration.
After repairs or module replacement, clear codes and perform full functional test of body systems and network communications. Recheck for reappearance of B0740.
Document all findings and, if necessary, consult manufacturer service information for module bench test or return/repair policies.