Code
B28D5
Generic
B — Body
Blind Spot Monitor Control Module Communication Fault
AI status
Completed
Completed
100%
Causes
- Faulty BSM control module
- Open/shorted or intermittent wiring between BSM and vehicle network
- Corroded or loose connectors at module or wiring harness
- Blown fuse or poor ignition/switched power to module
- CAN/LIN bus fault or gateway/module address conflict
- Software/configuration mismatch or required module reprogramming
Symptoms
- Blind spot indicator lamps not functioning
- Intermittent or no blind spot alerts
- Warning message or BSM lamp on dash
- Cross-traffic alert or lane-change assist unavailable
- Related systems (e.g., door modules, instrument cluster) show faults or loss of data
What to check
- Check for stored freeze-frame or related U-codes in network gateway or BCM
- Visually inspect BSM module connector and wiring for damage/corrosion
- Verify fuses and ignition-switched power to BSM module
- Check vehicle ground points shared by BSM module
- Scan network for other active communication faults (U-codes)
- Confirm recent service history for module replacements or software updates
Signal parameters
- Module supply voltage: battery voltage when key on (vehicle specific)
- Ground continuity to chassis ground (
- CAN bus idle voltages: CAN_H ~2.5 V, CAN_L ~2.5 V (differential signaling)
- Presence of periodic BSM CAN frames (ID and interval are manufacturer-specific)
- LIN (if used) signal present and within expected voltage levels
Diagnostic algorithm
- Retrieve all stored DTCs from BSM, BCM/gateway, and instrument cluster; note freeze-frame data
- Verify battery voltage and fuses supplying the BSM module
- Perform a visual inspection of the BSM module and harness; repair any physical damage or corrosion
- Check ground(s): measure resistance from BSM ground pin to chassis ground (
- Backprobe CAN high/low at the BSM connector with oscilloscope or multimeter to confirm activity and nominal voltages; compare to another module on same bus
- If bus is quiet or corrupted, isolate sections by disconnecting modules to locate short/open; inspect for pinbacks or shorted circuits
- If communication is present but messages invalid, check for other modules reporting U-codes (gateway issues) and clear codes then re-scan
- If wiring and bus are good, perform module self-test or attempt reprogramming/configuration per OEM procedure
- Replace BSM module only after confirming wiring, power, ground, and network integrity; program/configure new module as required
- Clear codes and verify system operation and that no related codes return
Likely causes
- BSM module internal failure
- Damaged CAN high/low wiring or short to battery/ground
- Poor ground at BSM module or shared ground point
- Connector pin corrosion/backshell damage at module
- Faulty gateway or other module failing to forward BSM messages
- Recently replaced or updated module not programmed/configured
Fault status
Status
Blind Spot Monitor control module communication fault — lost or invalid network messages to/from BSM.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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