Code
B297D
MITSUBISHI
B — Body
Body Control Module Communication Fault
Views:
UK: 7
EN: 9
RU: 6
AI status
Completed
Completed
100%
Causes
- Open, shorted, corroded or damaged wiring/connectors on CAN/LIN bus or BCM harness
- Blown fuse or loss of BCM power supply or ground
- Poor battery voltage or intermittent supply (low charge/voltage spikes)
- Failed or intermittent BCM or other network module
- Network termination or bus wiring short between CAN High and CAN Low
- Aftermarket electronics interfering with vehicle network
Symptoms
- BCM-related features intermittent or nonfunctional (interior lights, door locks, windows, wipers, remote keyless entry)
- Multiple communication-related DTCs present (loss of modules/messages)
- Instrument cluster warnings or erratic behavior of body systems
- Some convenience functions work only sporadically or after ignition cycles
- Vehicle may fail certain self-tests or require module reinitialization
What to check
- Retrieve all codes from all modules and note freeze frame / occurrence history
- Check battery state of charge and measure system voltage (with engine running and off)
- Inspect BCM fuses, relays, and power/ground connections for security and corrosion
- Visually inspect BCM connectors and wiring for damage, corrosion, or water intrusion
- Check for aftermarket devices tied into body wiring; disconnect if present
- Scan the CAN/LIN network with a capable scan tool to view message presence and bus error counters
Signal parameters
- Battery supply to BCM: ~12.0–14.5 V (engine off and running respectively)
- CAN bus idle voltages: CAN H ~2.5 V, CAN L ~2.5 V (differential ~0 V idle); differential swings to ~1–3 V during activity (vehicle-specific)
- Termination resistance across CAN H and CAN L: ~60 ohms (two 120 ohm terminators in parallel)
- Ground resistance at BCM: low ohms (near 0 Ω between BCM ground and chassis)
- Message presence: periodic BCM network messages should be seen on CAN/LIN (frequency varies by vehicle and message)
Diagnostic algorithm
- Read and record all DTCs from all modules; clear codes and see if B297D returns and when.
- Verify battery voltage and charging system health; ensure stable supply before further testing.
- Inspect BCM area visually for water, corrosion, or physical damage. Check connector locks and pin condition.
- Check BCM fuses and main relays; confirm BCM is receiving constant and switched power and has a good chassis ground.
- With a scan tool, monitor CAN/LIN bus traffic. Look for missing periodic messages from the BCM or high bus error counts.
- Measure CAN H and CAN L voltages at the BCM connector and downstream nodes with key on. Verify termination resistance (~60 Ω).
- Wiggle-test wiring and connectors while monitoring bus and DTCs to find intermittent faults.
- If a suspect module is isolated, disconnect non-essential modules or aftermarket devices to see if bus returns to normal.
- If wiring and power/grounds check good but communication still fails, try reprogramming or re-flashing BCM per manufacturer procedure; follow immobilizer/pairing steps if required.
- Replace BCM only after verifying wiring, power/ground, and network health. After replacement, perform necessary reprogramming and configuration.
Likely causes
- CAN bus open or short (CAN H to CAN L, CAN to ground, CAN to 12V) near BCM
- Loose or corroded connector pins at BCM or gateway module
- Blown BCM fuse or main power relay not supplying BCM
- Faulty BCM internal hardware or firmware error after recent battery replacement or jump start
- Faulty gateway/module upstream causing message loss
- Improperly installed aftermarket alarm/remote start tapping into body wires
Fault status
Status
BCM communication fault detected — the Body Control Module failed to communicate correctly on the vehicle network. This may be caused by power/ground loss, wiring/connector faults, bus termination issues, or module failure.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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