B29EE — Body Control Module Internal Communication Error

Causes

• BCM internal processor or memory fault
• Corrupted or incompatible firmware/software
• Intermittent or low power supply to BCM (battery/ignition feed)
• Poor or corroded ground or power connections at the BCM
• Severe CAN/LIN bus errors or bus shorting causing internal watchdog trips
• Water intrusion or physical damage to the BCM

Symptoms

• Loss or intermittent operation of body functions (locks, lights, windows, wipers)
• Warning messages or dash indicators related to body systems or communication
• Other modules report loss of communication with BCM or U-codes (e.g., U0100)
• Keyless entry, immobilizer or starting issues tied to BCM functions
• Unexpected module resets, stored miscommunication DTCs, or no response from BCM on scan tool

What to check

• Read all stored and pending DTCs from BCM and other network modules; record freeze frame and event counts
• Check battery voltage with key off and key on; verify stable 12.4–12.8V (engine off) and ~13.5–14.8V (engine running or charging)
• Inspect BCM connectors and harness for corrosion, water entry, bent pins, or loose terminals
• Verify BCM power and ground circuits for proper continuity and low resistance to chassis
• Scan for CAN/LIN bus error counters and verify presence of expected message IDs and frequencies
• Check for recent software updates, flashes, or body repairs that could have altered BCM programming

Signal parameters

• Battery voltage at BCM pin (V) — expected ~12.4–12.8 V (key off), ~13.5–14.8 V (running)
• Ground resistance at BCM chassis/power ground (
• CAN bus voltages (dominant/recessive levels ~2.5 V differential with ~2.5 V on each line idle)
• CAN bus message frequency and specific BCM message IDs (messages/sec or Hz)
• Bus error/frame error counters reported by scan tool
• LIN bus voltage and wake/sleep timing (if BCM uses LIN subnetwork)

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