B2905

Code

Generic B — Body

Passenger Seat Occupant Detection Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 6 EN: 12 RU: 14

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Page language: EN

Read and record all stored DTCs and freeze frame data with a qualified scan tool
Inspect seat cushion, upholstery and sensor mat for signs of water or mechanical damage
Visually inspect connectors (sensor and control module) for corrosion, bent pins, or loose terminals
Check relevant fuses and power/ground circuits for integrity
Wiggle test harness and connector while observing live data to reproduce fault
Confirm occupant detection status with known weights (empty seat vs. adult passenger or test weight)

Reference/shared supply: typically a regulated 5 V reference (verify with model-specific data)
Signal type: may be analog voltage (0–5 V range) or a digital message to the SRS module — signal should change when weight is applied/removed
Open-circuit condition: very high resistance or no signal (often >10 kΩ or no voltage present)
Short-to-ground: signal near 0 V; short-to-battery: signal near battery voltage (check for both fault conditions)
CAN/Central module systems: occupant status updates typically at low frequency (e.g., 1–10 Hz) — verify with factory scan tool
Resistance checks (if applicable): refer to vehicle service data; expect a finite resistance across sensor elements, not infinite

Connect a qualified scan tool and record DTCs, live data, and any freeze-frame information.
Clear the code, then attempt to recreate the fault to verify it returns and gather live-data behavior.
Visually inspect the passenger seat cushion area, sensor mat, and connectors for damage or moisture.
With key on (engine off) verify presence of reference voltage and ground at the sensor connector using a multimeter. Note values.
Observe the sensor signal (or occupant status) while applying/removing a known weight to the seat. Confirm the signal changes as expected.
Perform continuity/resistance checks on the sensor signal, reference and ground circuits between the sensor connector and the airbag/occupant detection module. Repair any opens or shorts.
Wiggle the harness and connectors while watching live data to find intermittent faults; inspect for chafing where the harness crosses the seat frame.
If electrical checks are good but the signal does not respond correctly, remove and bench-test or replace the sensor mat/load cell per service procedure, or replace the occupant detection module if indicated by module diagnostics.
After repairs, clear DTCs and verify correct operation through live data and by confirming passenger airbag enable/disable logic and warning lamp behavior.
If intermittent or unclear, consult vehicle-specific service manual and wiring diagrams; consider dealer/OEM diagnostic procedures for SRS and occupant detection systems.