Code
B1C34
MITSUBISHI
B — Body
Body Control Module CAN Communication Error
Views:
UK: 16
EN: 27
RU: 21
AI status
Completed
Completed
100%
Causes
- Low or unstable battery voltage
- Blown fuse(s) supplying BCM or CAN bus
- Poor or corroded ground(s) at BCM or common chassis grounds
- Damaged, shorted or chafed CAN wiring/connectors
- Faulty BCM (hardware or internal CAN transceiver)
- Missing or failed CAN bus termination resistor(s)
Symptoms
- Instrument cluster or warning lights related to body systems
- Loss or intermittent operation of door locks, interior lights, remote keyless entry, windows or wipers
- Other modules reporting communication-related fault codes
- Reduced or no response from BCM-controlled features
- Possible illumination of general network or malfunction indicator lamp
What to check
- Verify battery voltage (with key off and key on) and battery health
- Inspect BCM fuses and relays; replace any blown fuses
- Visually inspect BCM connector(s) for corrosion, bent pins, or water ingress
- Check and clean BCM ground(s) and ensure tight chassis connection
- Measure resistance between CAN_H and CAN_L with ignition off (nominal ~60 ohms) to verify termination
- Check wiring harness for physical damage near doors, hinges, trunks — common flex points
Signal parameters
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each)
- Dominant state typical example: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential present)
- Expected bus termination: two 120 Ω resistors in parallel ≈ 60 Ω across CAN_H and CAN_L
- Normal CAN bitrate as vehicle spec (commonly 250 kb/s or 500 kb/s depending on network) — confirm with manufacturer data
Diagnostic algorithm
- Record freeze frame/related codes and symptoms and note when faults occur (key on, start, accessory, driving)
- Check battery voltage and charging system; repair as needed to ensure stable supply
- Inspect BCM fuses and power feed circuits; replace any failed fuses and recheck communication
- Visually inspect BCM connectors for corrosion, bent pins, broken wires; repair or replace damaged connectors
- Check and clean BCM ground points; verify low resistance to chassis and battery negative
- Measure resistance across CAN_H and CAN_L (ignition off) — expect ~60 Ω. If open or high, trace for disconnected termination or open wiring
- Using a multimeter or preferably an oscilloscope, probe CAN_H and CAN_L for idle and active waveforms; look for missing signals, noise, or bus shorts to battery/ground
- If a short is suspected, isolate segments by disconnecting connectors to identify the faulty branch or module
- Use the scan tool to attempt reflash/reprogramming of BCM only after eliminating wiring faults and confirming stable power/ground
- If wiring and external modules check OK and the BCM still fails to communicate, consider replacing the BCM per manufacturer procedure and program new unit
- Clear codes and perform a test drive; monitor for recurrence and verify restored functionality
Likely causes
- Corroded BCM connector pins or poor ground connection
- Short to power or ground on CAN_H or CAN_L wiring at a wiring harness splice or connector
- Open or high-resistance CAN bus termination (faulty or disconnected resistor)
- Failed BCM CAN transceiver or internal electronics
- Vehicle battery recently disconnected and module needs reprogramming
Fault status
Status
Body Control Module CAN communication error: BCM is not communicating correctly on the vehicle CAN bus. May be intermittent or permanent loss of CAN messages to other modules.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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