B3501

Code

Generic B — Body

Airbag Passenger Seat Occupant Detection Fault

Brand: Generic

Type: B — Body

Views: UK: 5 EN: 14 RU: 5

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Page language: EN

Faulty passenger seat occupant sensor (pressure/weight or capacitance mat)
Damaged wiring, pinched harness or corroded connector at the seat or control module
Poor ground or intermittent power supply to the occupant detection system
Faulty Restraint Control Module (RCM) / Airbag control unit or internal software fault
Aftermarket seat covers, seat repairs, or foreign objects interfering with the sensor
Water intrusion or contamination of the seat sensor

Airbag/SRS warning lamp illuminated or flashing
Passenger airbag OFF/ON indicator incorrect or not changing with occupant presence
Inability to enable/disable passenger airbag as expected
Possible related warnings (seat belt light) or vehicle entering reduced airbag mode

Retrieve DTCs and freeze frame data with a capable scan tool; log present/historic codes
Check battery voltage (should be stable >12V) and charging system before diagnosing SRS faults
Visually inspect passenger seat, underside, connectors and harness for damage, corrosion or water intrusion
Check for aftermarket seat covers or items on seat that could mask weight reading
Wiggle-test harness/connectors while monitoring DTCs to find intermittent faults
Check related fuses and ground connections

Occupant sensor reference voltage — typically ~5 V reference (verify with service data)
Occupant sensor signal range — typically 0–5 V varying with load/position (manufacturer-specific)
Seat mat resistance/impedance — varies with load; consult OEM data for expected values
Diagnostic bus messages — Occupant Classification System data present on CAN/LIN (scan tool should show occupancy status and sensor values)
RCM status codes/payload — expected occupancy state codes (e.g., empty/child/adult) available via scan tool

Read and record DTCs and freeze-frame data with an SRS-capable scan tool; note any other related codes
Verify vehicle battery voltage and charging; charge if low and clear codes to retest
Perform visual inspection: seat upholstery, sensors/mats, connectors, pins and wiring under the seat for damage, moisture or corrosion
With ignition ON, monitor occupant sensor values on a diagnostic tool while a known weight (adult) sits in different positions; compare to expected PID values per service data
Perform connector wiggle test while monitoring for code or PID changes to find intermittent wiring faults
Check continuity and resistance of occupant sensor circuits per OEM procedures; replace mat if out of spec
Inspect and test grounds and power feeds to the occupant detection system
If wiring and connectors are good, perform SRS/OCS relearn or calibration procedure per manufacturer service manual, then recheck
If fault persists after wiring and calibration verified, consider replacement of the occupant sensor mat or RCM as guided by manufacturer diagnostic flow
After any repair, clear DTCs and perform functional test and final road/test seat occupant detection verification
Always follow SRS safety precautions: disable airbag system power per manufacturer procedure (disconnect battery and wait specified time) before removing or servicing seats or connectors

Damaged connector or wire harness under the seat (broken, chafed or corroded)
Malfunctioning occupant detection mat/sensor in the passenger seat
Poor ground or low battery voltage at time of fault
Recent seat removal, replacement or reupholstery not followed by required calibration/relearn