B01A0

Code

Generic B — Body

Body Control Module Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 20 RU: 9

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Low or missing battery voltage / poor battery condition
Blown or corroded BCM-related fuse or fusible link
Loose, corroded, or damaged BCM power/ground connections
Broken, shorted or high-resistance CAN/LIN wiring or connectors
Faulty termination (missing/shorted CAN terminator) or incorrect bus voltage
Intermittent connector contact (pin corrosion, bent pins)

Symptoms

No response from BCM-controlled features (door locks, lighting, windows, etc.)
Intermittent or permanent loss of instrument cluster messages or warning lights
Multiple modules reporting communication faults
Keyless entry, start/stop, or immobilizer problems
Erratic lighting, door ajar warnings, or convenience feature failures
Stored or active communication-related DTCs (U-codes, additional B-codes)

What to check

Verify good battery condition and resting voltage (>= 12.4 V) and charging system operation
Check BCM-related fuses and fusible links for continuity and correct rating
Visually inspect BCM connector(s) and harness for corrosion, water damage, pin damage or disconnected plugs
Use scan tool to confirm BCM presence on the network and list other lost-communication codes
Measure CAN_H and CAN_L voltages at the BCM connector with ignition ON and engine OFF
Measure bus termination resistance (approx. 60 ohms total between CAN_H and CAN_L across the bus)

Signal parameters

CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V
CAN bus dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V)
Typical termination resistance: ~60 ohms measured across CAN_H and CAN_L (two 120 Ω terminators in parallel)
LIN bus idle: near battery voltage when idle; data pulses pull low (vehicle-specific)
Expected scanner response: BCM should appear on network and respond to diagnostic requests; lost/missing = communication fault

Diagnostic algorithm

Confirm and record all stored DTCs and freeze-frame data with a capable scan tool; note if other modules report lost communication.
Verify battery state of charge and charging system; ensure stable voltage during testing and repairs.
Inspect BCM fuses and relays; replace any blown or corroded components and retest.
Visually inspect BCM connectors and wiring for physical damage, corrosion, or signs of water intrusion; repair as needed.
With ignition ON, use DVOM or oscilloscope to measure CAN_H and CAN_L at the BCM connector: check idle voltages and dominant levels during activity and verify termination resistance (~60 Ω).
Perform wiggle/connector stress tests while watching live network data for dropouts or errors. Isolate sections by disconnecting harness branches or peripherals to locate intermittent faults.
Remove or disable aftermarket devices and check whether communication returns.
If wiring, power and grounds are verified good and network signals are correct, attempt module reset/clear codes and re-scan. If intermittent persists, check for required software updates or reflash BCM calibration per OEM procedure.
If all wiring and software steps are complete and BCM remains unresponsive or shows internal faults, replace BCM and program/configure/relearn as required. Verify restoration of network communications and proper operation of BCM-controlled features.
After repair, clear codes and road-test/operate affected features to confirm the fault is resolved and no new communication codes appear.

Likely causes

Battery voltage low or intermittent (most common cause of network issues)
Loose/poor ground or power feed to BCM
Damaged CAN bus wiring or connector at BCM or gateway
Missing/failed CAN terminator causing incorrect bus impedance
Corrupted BCM software or failed module after electrical event
Aftermarket alarm/remote start interfering with bus communications

Fault status

⚠️ Status

BCM communication fault detected — module not responding or network errors present. Intermittent or persistent loss of communication with the body control module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.5 hours