Code
B3642
HUMMER
B — Body
Body Control Module (BCM) Internal Fault
Views:
UK: 9
EN: 11
RU: 8
AI status
Completed
Completed
100%
Causes
- Defective BCM (internal hardware or firmware fault)
- Low or intermittent battery voltage / poor battery connections
- Corroded, damaged, or loose BCM connectors or wiring
- Water intrusion or physical damage to BCM or harness
- Software corruption requiring reprogramming
- Related fuse or power supply circuit fault
Symptoms
- Multiple body functions intermittent or inoperative (door locks, lighting, wipers, dome lights)
- Warning or information lamps/messages on dash related to body systems
- Erratic or no CAN network communication with BCM
- Blown fuses related to BCM circuits
- Stored DTCs for other modules due to loss of BCM messages
What to check
- Read all stored DTCs and freeze frame data with a capable scan tool (include U-codes)
- Check battery voltage (with engine off and cranking); inspect battery terminals and ground straps
- Visually inspect BCM connector(s) and harness for corrosion, bent pins, water, or physical damage
- Verify fuses and relays supplying BCM power and ignition feed
- Check CAN/LIN bus status and other module responses (bus voltage and message traffic)
- Attempt to clear the code and see if it returns; capture conditions when it returns
Signal parameters
- BCM supply voltage: nominal ~12V (13.5–14.8V with engine running) — should be stable
- Battery voltage during key-on: not dropping below ~11.5V
- Ground continuity: BCM ground to chassis
- CAN high/low idle voltages: approx. CAN_H ~2.5V, CAN_L ~2.5V (differential ~0V idle, ~2V during dominant)
- CAN bus message rate: consistent with other modules; no long bus-off conditions
- Module wake/sleep control signals present as specified by factory data
Diagnostic algorithm
- Connect a factory-level scan tool. Read and record all DTCs, freeze frame, and pending codes. Note any U-codes (communication errors).
- Verify battery state of charge and charging system. Ensure battery terminals and ground straps are clean and tight.
- Inspect BCM connector and mating harness for corrosion, bent pins, moisture, or damage. Repair any wiring/connectors found faulty.
- Verify BCM power and ground circuits at the module pins with a multimeter: supply voltage with key ON/engine running, ground continuity to chassis.
- Check CAN/LIN bus physical layer: measure bus voltages, check termination, and verify message traffic with the scan tool or scope. Isolate a bus fault if present.
- If wiring and power/ground check OK and communications healthy, attempt to clear codes and reproduce. If the code returns persistently under normal conditions, follow reprogramming procedures.
- Check for and apply any manufacturer software updates or calibrations for BCM. Reflash or reprogram the BCM per service procedures if applicable.
- If reprogramming fails or fault persists and all electrical checks pass, consider BCM replacement. After replacement, program and configure (vehicle personalization/teach-in) the new BCM and verify system operation.
- After repairs, clear codes and perform a full system check; confirm no related modules report new or pending faults.
Likely causes
- BCM internal electronics failure
- Poor battery/charging system voltage during module operation
- Corroded connector pins at BCM or harness splice
- Unstable CAN bus causing BCM internal fault recognition
- Previous improper programming or interrupted calibration
Fault status
Status
BCM internal fault — internal module error detected. May require power/ground/wiring repair, software update, or module replacement and programming.
Repair difficulty: Hard
Diagnostic time: 2-4 hours
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