B3719

Code

Generic B — Body

Occupant Detection Sensor Circuit Fault

Brand: Generic

Type: B — Body

Views: UK: 2 EN: 3 RU: 5

AI status

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Page language: EN

Causes

Damaged or corroded connector at the seat occupancy sensor or airbag control unit
Broken, chafed or shorted wiring in the seat harness (under-seat area)
Faulty occupant detection mat/sensor module (pressure, weight or capacitance sensor)
Poor or missing ground or supply (blown fuse, damaged power feed)
Moisture or liquid intrusion into the seat mat or connector
Aftermarket seat covers or accessories interfering with the sensor

Symptoms

SRS / airbag warning light illuminated on dash
Passenger airbag status indicator may show incorrect on/off state
Seat-occupant detection not registering (passenger always shown as absent or present)
Seatbelt reminder or chime behavior may be incorrect
Stored B3719 (and possibly related SRS codes) in the airbag/BCM memory

What to check

Read and record all SRS/airbag codes and freeze-frame data with a capable scan tool
Visually inspect seat cushion, underside of seat, connectors and harness for damage, corrosion, or moisture
Check for aftermarket seat covers or objects on the seat that could affect the sensor
Inspect and verify related fuses and power/ground points for the SRS/occupant system
Use a scan tool to monitor occupant detection live data while an adult sits in the seat and when empty
Wiggle the seat wiring harness and connectors while monitoring live data and codes to reproduce fault

Signal parameters

Reference/supply voltage (typical): ~5 V reference or vehicle-specific supply (0 V to 12 V possible depending on design)
Signal voltage (typical): varies by design — with no occupant a low-level signal near reference low (~0.2–1.0 V) and with occupant signal typically rises into 1–4.5 V range; some systems use digital/capacitance values instead
Line resistance: open/very high when connector disconnected; low and stable continuity to module when intact (exact ohms vary by vehicle)
Note: exact voltages, resistance and communication protocol vary by manufacturer — always compare to OEM specifications

Diagnostic algorithm

Safety first: follow vehicle manufacturer's SRS safety procedures before probing connectors. Disable vehicle battery if required by the service manual and wait specified time before disconnecting SRS components.
Read codes and freeze frame with a qualified scan tool; note any other SRS codes stored.
Perform a visual inspection of the passenger seat cushion, underside, harness, connectors and airbag module for damage, corrosion, water ingress or foreign objects (including aftermarket covers).
Verify relevant fuses and power/ground points are present and secure.
Reconnect battery if removed and use scan tool to view live occupant detection data. Have an adult sit in various positions (centered, forward) and observe signal changes; then leave seat empty and observe. Look for expected change in live values or 'occupied' status.
With ignition off and battery disconnected if required, check continuity and resistance of the sensor harness from the seat connector to the airbag/occupant classification module. Repair any opens/shorts.
With ignition on and proper safety approach, backprobe connector and measure reference voltage and signal while repeating the occupied/unoccupied test. Check for intermittent change while wiggling harness/connectors.
If wiring and connectors are good but sensor signal is out of range or does not change with weight, replace the occupant detection mat/module per OEM procedure.
After repair/parts replacement, clear codes and perform any required occupant classification calibration, sensor learn or airbag module reset per manufacturer instructions.
If code persists after sensor and wiring replacement, consider airbag/control module fault and refer to manufacturer diagnostics or replace the module as last resort.

Likely causes

Loose or corroded connector at the seat occupancy sensor
Damaged wiring in the seat harness (pinched under the seat)
Defective occupant detection mat/module
Moisture ingress to the seat sensor or connector

Fault status

⚠️ Status

Occupant detection (passenger) sensor circuit fault detected — system may misclassify passenger presence; SRS warning light on. Inspect seat sensor, wiring and connectors and follow SRS safety procedures.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours

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