B133C

Code

Generic B — Body

Body Control Module Internal Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 4 EN: 4 RU: 2

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Intermittent or low battery/charging system voltage
Poor or corroded power or ground connections to the BCM
Damaged wiring harness or connectors at the BCM
CAN/LIN bus faults or excessive bus traffic/noise
Software corruption, failed firmware update, or configuration mismatch
Internal BCM hardware failure (processor, memory, transceiver)

Symptoms

One or more body systems work intermittently or not at all (locks, lights, wipers, interior lamps)
Multiple unrelated warning lights or system messages on dash
No response from remote keyless entry or intermittent key recognition
Unexpected door ajar, airbag, or ABS faults that appear with body communication loss
Vehicle may not enter expected accessory/ignition behaviors

What to check

Read all stored DTCs (BCM and all network modules) and freeze frame/occurrence data with an OEM-capable scanner
Check battery state-of-charge and charging system voltage (engine running ~13.5–14.8 V; key on ~12.0–12.8 V)
Inspect BCM fuses, fusible links and relays for continuity and correct rating
Visually inspect BCM connector(s) and harness for corrosion, bent pins, water intrusion, chafing or damage
Verify good chassis and battery grounds at BCM (measure resistance to battery negative; should be very low)
Scan CAN/LIN bus for bus-off conditions or other network errors

Signal parameters

Battery supply to BCM: ~11–15 V depending on key/engine state (key on ~12 V, running ~13.5–14.8 V)
Ground resistance from BCM ground pin to battery negative:
CAN bus idle voltages: CAN H ≈ 2.5 V, CAN L ≈ 2.5 V; dominant state ~3.5 V / ~1.5 V respectively (use scope for differential check)
ABS/other module communication status bits/messages present on network (use diagnostic tool to confirm message counters)
LIN bus voltage levels and wake/sleep signals per manufacturer spec if LIN used

Diagnostic algorithm

Record all codes and module communication status. Note if code is permanent or intermittent and any related codes in other modules.
Verify battery voltage and charging system. Recharge or replace battery if below specification and retest.
Inspect and test BCM fuses, relays and visible connector pins for corrosion or damage; repair or replace as needed.
Backprobe/check power and ground at BCM with connector connected: confirm proper supply voltage and low ground resistance.
Scan the vehicle network: check for bus errors, messages from other modules, and perform a module network health check.
Use an oscilloscope to verify CANH/CANL idle and dominant waveforms and to look for noise or reflections on the bus.
Wiggle-test wiring harness while monitoring bus and BCM status to try to reproduce fault and locate intermittent harness faults.
Check for water intrusion or physical damage to BCM; dry and clean connector area if contamination found.
If wiring, power and ground are good, attempt soft reset/reboot of BCM per manufacturer procedure (battery disconnect or scan tool reboot) and re-scan.
Check for available software updates or reflash the BCM with OEM diagnostic equipment if advised by manufacturer.
Replace the BCM only after confirming all wiring, power, ground and network faults are resolved; program and configure new module per OEM procedure.
After repair, clear codes and road-test to verify fault does not return; re-check module communications and related system operation.

Likely causes

Weak battery or poor battery terminal connection causing supply undervoltage
Poor ground at BCM (loose bolt, corrosion)
Contaminated/damaged BCM connector(s) or pinned wiring shorted/open
CAN bus short to voltage/ground or missing bus termination
BCM software glitch or corrupted calibration requiring reflash
Failed BCM electronics requiring replacement

Fault status

⚠️ Status

Body Control Module reports an internal communication fault. The module detected failure or corruption in internal message processing or network interface. Further diagnosis required to confirm cause (power/ground, wiring, software, or internal hardware).

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.0-4.0 hours