B13B7

Code

Generic B — Body

Body Control Module — Blind Spot Sensor Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 6 EN: 10 RU: 7

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Page language: EN

Causes

Damaged or corroded wiring or connector between BCM and blind spot sensor
Faulty blind spot sensor (radar/ultrasonic) or internal electronics
Intermittent or lost power or ground to the sensor
CAN/LIN bus fault, high bus error rate, or termination problem
Faulty BCM or BCM software/configuration error
Blown fuse or auxiliary power issue for sensor circuit

Symptoms

Blind spot warning unavailable, disabled, or shows error icon
False or missing blind spot alerts
Warning message or lamp on instrument cluster referencing blind spot or sensors
Related systems that use blind spot input reduced or disabled (lane-change assist)
Stored communication fault codes in BCM and/or sensor modules

What to check

Read all stored and pending DTCs from BCM and related modules; record live data if available
Check for other network-related codes (U-codes) that indicate wider bus issues
Visually inspect sensor connectors and wiring harnesses for damage, corrosion, or water ingress
Verify fuses and relay(s) supplying sensor circuits and BCM power/ignition feeds
Check battery voltage and vehicle ground quality
Use a scan tool or scope to confirm presence and rate of messages from the blind spot sensor(s)

Signal parameters

Vehicle battery nominal voltage: ~11–14.5 V during normal operation (verify at sensor power pin)
CAN bus idle voltages (approximate): CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V; dominant state differential ≈ 1.5–3.0 V
Expected message presence: blind spot sensor messages typically repeat at a steady rate (manufacturer dependent); absence or long gaps indicate timeout
Low-level wiring: check for continuity (near 0 ohms) on power/ground, and expected resistance on CAN/LIN pairs (should not be open)
Look for excessive bus error counts or CRC failures reported by a diagnostic tool

Diagnostic algorithm

Connect a capable diagnostic scanner and read BCM and related module codes and live data. Note sensor presence flags, message IDs, and any network errors.
Attempt to reproduce the fault by cycling ignition and exercising blind spot functions; watch live message rate and error counters.
Visually inspect blind spot sensor(s), connectors, and wiring for corrosion, bent pins, water intrusion, or physical damage. Repair any obvious damage.
Verify power and ground at the sensor connector with key ON. If power or ground is missing, trace wiring back to fuse/relay/ground point and repair.
Check fuses and relays for the sensor/BCM circuits; replace if blown and investigate cause of blow if present.
Use a scan tool / CAN bus monitor or oscilloscope to confirm the blind spot sensor’s network messages appear on the bus. If messages are absent, test wiring continuity between sensor and bus/BCM.
Wiggle-test connectors and harness while observing live data to find intermittent faults. Repair or replace harness/connector as needed.
If a single sensor is suspected, swap with a known-good sensor (if available) or temporarily disconnect to observe change in code behavior.
If wiring and sensor check good but communication errors continue, check BCM software level and configuration; reflash or update per manufacturer service instructions and re-run diagnostics.
After repairs, clear codes and road-test to confirm the fault does not return. Verify correct system behavior and perform any required calibration or adaptation procedures.