B3194

Code

Generic B — Body

Body Control Module (BCM) Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 4 EN: 3 RU: 1

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Page language: EN

Causes

BCM internal hardware failure (processor, memory, power regulation)
Corroded or loose BCM connector or wiring harness
Low or unstable battery voltage / poor ground
Water intrusion or physical damage to BCM
Software corruption or failed module boot/reflash
Shorts, opens, or intermittent CAN/LIN bus communications

Symptoms

Multiple body electrical functions inoperative or intermittent (locks, lights, wipers, interior electronics)
Warning lights or message cluster indicating electrical module fault
Loss of communication with BCM on diagnostic tool (U-codes or timeouts)
Battery drain or unable to enter sleep/standby modes
Unusual behavior after jump start, battery replacement, or water exposure

What to check

Retrieve all stored and pending DTCs and freeze frame data from the BCM and other modules
Verify battery voltage at rest and during cranking (12.4–12.8 V resting; >10 V during cranking typical)
Inspect BCM connector(s) for corrosion, bent pins, water intrusion, or damage
Check fuses and power/ground circuits supplying the BCM for correct continuity and voltage
Scan for related communication codes (U0100, U0140, U0073, U0401) and check CAN/LIN integrity
Perform wiggle testing on harness while monitoring live data for intermittent faults

Signal parameters

Battery/supply voltage at BCM pin (V)
Main ground resistance/continuity (ohms)
CAN bus voltage levels and recessive/dominant states (approx. 2.5 V idle on many networks)
CAN/LIN error counters and message rates from scan tool
Module internal uptime/restarts or watchdog reset count (if available)
Sleep/wake command and ignition status messages visible on bus

Diagnostic algorithm

Read and record all DTCs and freeze frame data from BCM and related modules. Note occurrence conditions.
Verify good battery condition and charging system. Recharge or replace battery if low and retest.
Visually inspect BCM and harness for corrosion, water damage, rodent damage, or loose connectors. Clean and secure as needed.
Check power and ground pins at BCM for correct voltage and low resistance to chassis ground. Repair wiring or grounds that fail.
Scan CAN/LIN networks for communication faults. Use oscilloscope or high-quality scan tool to verify message traffic and bus health.
With a scan tool, monitor BCM internal parameters (uptime, reset count, supply voltage) while performing wiggle/operational tests to reproduce fault.
If wiring and power/ground are good, check for and apply any official software updates or reflash BCM per manufacturer procedure.
If module still reports internal fault after verified wiring, power, and software, consult manufacturer repair information. Replace BCM only after confirming external causes are eliminated and following proper programming/initialization procedures.
After repair or replacement, clear codes and perform full system test to confirm fault does not recur.

Likely causes

Corrosion or moisture at BCM connector causing intermittent internal resets
Battery or charging system problem causing undervoltage to BCM
Failed internal voltage regulator or capacitor inside BCM
Lost or corrupted firmware requiring reflash
CAN bus fault causing module watchdog to trigger internal fault

Fault status

⚠️ Status

BCM detected an internal error (hardware, firmware, or internal communications fault). Module may be unreliable until root cause (power, grounding, wiring, water damage, or software) is resolved.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4.0 hours