Code
B2025
Generic
B — Body
Body Control Module Communication Error
AI status
Completed
Completed
100%
Causes
- Open, shorted or corroded wiring or connector at the BCM or network nodes
- Battery voltage low or poor battery/charging system condition
- Blown fuse or poor power/ground to the BCM
- CAN/LIN bus short to battery or ground, missing termination resistors
- Faulty BCM (internal electronics or firmware)
- Aftermarket electronic device interfering with the vehicle network
Symptoms
- Multiple modules not responding to scan tool or intermittent module availability
- Nonfunctional body features (lights, locks, windows, wipers) or erratic operation
- Vehicle may not crank or will show immobilizer/security faults
- Accessory functions lost after start or during driving
- Communication-related trouble codes present (U-codes) or stored BCM faults
- Possible warning lights on instrument cluster
What to check
- Use a capable scan tool to read all modules and note communication and U-codes
- Check battery voltage and charging system (key ON, engine OFF should be ~12.4–12.8 V)
- Visually inspect BCM connector(s) and harness for corrosion, bent pins, water intrusion, or damage
- Verify fuses and power/ground circuits feeding the BCM
- Measure CAN bus voltages (CAN_H/CAN_L) at the BCM connector with key ON
- Inspect for aftermarket devices tied into the bus; disconnect and retest
Signal parameters
- CAN bus idle voltages (recessive): CAN_H ≈ 2.4–2.6 V, CAN_L ≈ 2.4–2.6 V
- CAN bus dominant state: CAN_H ≈ 3.5–3.9 V, CAN_L ≈ 1.1–1.5 V
- Measured differential voltage when dominant ≈ 1.5–2.5 V
- Bus termination: two 120 Ω resistors in parallel ≈ 60 Ω across CAN_H and CAN_L
- Common network data rates: 125 kb/s, 250 kb/s, 500 kb/s (verify vehicle spec)
Diagnostic algorithm
- Connect a scan tool to retrieve BCM code and any related U-codes. Record freeze-frame and module presence.
- Check battery state-of-charge and charging system. Recharge or replace if below specified levels before proceeding.
- Visually inspect BCM connectors and harness for damage or contamination. Repair any obvious faults.
- Verify BCM power and ground circuits with a multimeter; check associated fuses and relays.
- With key ON (engine OFF) measure CAN_H and CAN_L at the BCM connector. Compare to signal parameters and check for stuck-high/low or missing bus.
- Check continuity between BCM pins and other network nodes; look for short to ground/power.
- If bus voltages abnormal, isolate sections of the network (disconnect modules or harness branches) to locate the faulted segment or device.
- Remove aftermarket devices or accessories and retest communication.
- If wiring and power/ground are good and bus is healthy but module still not responding, check for required software updates or module programming. Reflash or reprogram per manufacturer procedures.
- Replace the BCM only after all wiring, power, ground, and bus issues are ruled out. Program/configure replacement module to vehicle and verify operation.
- Clear codes and road-test. Re-scan to confirm the code does not return.
Likely causes
- Damaged/abraded CAN wiring in harnessing (door sills, harness chafing)
- Corroded or loose BCM connector pins causing intermittent contact
- Weak battery causing modules to enter safe/fail states
- Failed termination (missing/burned 120 ohm resistor pair) causing bus instability
- Recent service or module replacement not programmed to vehicle
Fault status
Status
Body Control Module communication fault — module not communicating correctly on vehicle network.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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