B29A0

Code

Generic B — Body

Body Control Module Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 9 EN: 30 RU: 13

AI status

Completed

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Page language: EN

Causes

BCM internal hardware failure (processor, memory, power regulation)
Corrupted or failed BCM firmware/flash
Loss or glitch of BCM supply voltage or ground
Water ingress or physical damage to BCM
Intermittent or shorted wiring to the BCM
Faulty CAN/LIN bus transceiver inside BCM

Symptoms

One or more convenience functions not working (locks, windows, dome lights, wipers)
Intermittent or permanent dashboard warning lamp(s) related to body systems
Loss of communication with BCM via scan tool (NO COMM / timeout)
Random or constant DTCs related to body functions
Erratic lighting behavior (DRL, interior lights, exterior lights)
Vehicle entering fail-safe or degraded mode for affected features

What to check

Scan vehicle with OEM-level diagnostic tool; read all BCM and network faults, freeze frame and event data
Verify battery state-of-charge and cranking voltage (should be ~12.4–12.8 V at rest, ~11–14.5 V during events)
Inspect BCM connectors for corrosion, bent pins, water stains, or contamination
Verify solid ground(s) and power supply(s) at the BCM (measure voltage and resistance to chassis)
Check fuses and relays feeding BCM circuits
Confirm CAN/LIN network health: bus voltages, termination resistance and presence of other module messages

Signal parameters

BCM supply voltage: key-off ~12.0–12.8 V; key-on/run 12–14.5 V
Ground continuity:
CAN High/Low idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (depending on vehicle)
Presence of periodic BCM CAN frames/messages when powered (frequency and IDs per vehicle spec)
Wake/sleep state transitions: module should respond to wake commands and go to sleep within specified time
Current draw: abnormal high quiescent current at BCM may indicate internal short or fault

Diagnostic algorithm

Record the trouble code(s), freeze frame and any related codes from all control modules. Note conditions when code set.
Clear codes and attempt to reproduce the fault under the same conditions. Retest to confirm persistent fault.
Check battery condition and charging system. Ensure stable supply before continuing diagnostics or reflash attempts.
Visually inspect BCM and harness connectors for corrosion, water ingress, physical damage and repair as needed.
Verify power and ground at the BCM with a DVOM. If supply/ground faults found, repair wiring and retest.
Check CAN/LIN bus activity with a scan tool or oscilloscope. Confirm BCM transmits/receives expected messages. Investigate bus errors or shorted nodes.
If wiring and network are good, check for available software updates or TSBs. Perform BCM reflash/update per OEM procedure with stable power.
If reflash does not clear the fault, consider swapping in a known-good BCM (programmed/configured for vehicle) to confirm internal hardware failure before module replacement.
If replacement BCM is required, follow OEM procedures for coding, immobilizer pairing and configuration to the vehicle.
After repair/reprogramming, clear codes and verify all related systems and communications return to normal and that the code does not recur.

Likely causes

Low or unstable battery voltage during key events or reprogramming
Poor ground or corroded connector pins at BCM
Known software bug requiring module reflash or calibration
Water intrusion at BCM housing or connector
Failed internal voltage regulator or transceiver on BCM board

Fault status

⚠️ Status

Body Control Module internal fault detected. Module self-test indicates malfunction or corrupted software/firmware. Verify power, grounds, and communications; reprogram or replace BCM if fault persists.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.0-3.0 hours