B0271

Code

Generic B — Body

Body Control Module communication fault

Brand: Generic

Type: B — Body

Views: UK: 19 EN: 23 RU: 20

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Multiple body functions (locks, lights, wipers, interior lamps) inoperative or intermittent
Instrument cluster or message center displays communication warning
Unable to communicate with BCM using a diagnostic scan tool
Intermittent or persistent fault codes related to other modules (lost comm)
Battery drain or unexpected parasitic current in some cases
Erratic behavior of convenience features (remote, keyless entry, etc.)

Read live data and module presence with a professional scan tool; note time stamps and fault freeze frames
Visual inspection of BCM connectors for corrosion, bent pins, moisture, or damage
Check fuses and fusible links related to BCM power feeds
Verify battery voltage (12.4–12.8 V resting; 13.5–14.8 V charging) and inspect battery terminals
Measure BCM power and ground circuits for good continuity and low resistance
Inspect CAN/LIN wiring for chafing, breaks, or aftermarket splices

CAN bus recessive voltage: approx. 2.5 V (both CANH and CANL near 2.5 V)
CAN bus dominant voltages: CANH ≈ 3.5 V, CANL ≈ 1.5 V during transmission
Expected CAN bus speeds: commonly 250 kbps or 500 kbps (verify vehicle spec)
LIN bus idle nominal: ~12 V to 0 V pulses (verify LIN wiring and master frames)
Message frequency: BCM should transmit and receive regular messages (scan-tool network node list)
Terminal voltages: BCM Vbat ≈ battery voltage; key-on accessory supply per vehicle spec

Connect a scan tool and confirm B0271 is current or historic; record freeze frame and related codes.
Attempt to communicate with the BCM. If the tool cannot connect, note whether other modules are accessible.
Perform a visual inspection of BCM connectors and nearby wiring for corrosion, moisture, or mechanical damage.
With ignition off, disconnect BCM connector(s) and inspect pins for corrosion, bent/broken pins, or pushed-out terminals.
Check fuses and fusible links supplying the BCM; replace any blown fuses and re-test communication.
Measure continuity and voltage on BCM power and ground pins (key off and key on as required). Repair high resistance or open circuits.
Backprobe CAN high and CAN low at the BCM and at a known-good module to compare voltages and waveform behavior; use oscilloscope if available to confirm proper recessive/dominant signaling.
If CAN is bus-off or stuck dominant, isolate segments by disconnecting branches or suspected modules until normal bus behavior returns; repair the shorted/failed module or wiring branch.
If wiring and power/ground check good, perform module reprogramming/configuration or reflashing per manufacturer procedures and re-run diagnostics.
If communication still fails after wiring and software checks, consider BCM replacement as a last step. Follow proper programming and coding procedures for replacement modules.
Clear codes and road-test to confirm repair; monitor for recurrence and check for related module faults.