B119B

Code

Generic B — Body

Occupant Classification Sensor Circuit Fault (Passenger Seat)

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 14 RU: 11

AI status

Completed

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Page language: EN

Causes

Damaged or shorted wiring harness to the occupant classification sensor (OCS) or seat module
Corroded, loose, or disconnected connector at the sensor or control module
Faulty occupant classification sensor mat/module in the passenger seat
Water/moisture ingress or contamination into the seat cushion or sensor
Aftermarket seat cover, seat repair, or improper reinstallation of seat components
Faulty seat control module or body control module (BCM) that processes OCS data

Symptoms

Airbag warning lamp illuminated on instrument cluster
Passenger airbag may be disabled or not deploy as expected (indicator may show 'PASSENGER AIRBAG OFF')
Possible diagnostic trouble codes stored related to occupant classification or airbag system
Inability to clear code or recurring code after clearing
Seat belt reminder or other seat-related warnings in some vehicles

What to check

Retrieve all airbag/occupant classification DTCs and freeze-frame data with a capable scan tool
Check for Technical Service Bulletins (TSBs) or recalls related to occupant classification
Visually inspect passenger seat area for signs of water damage, stains, or foreign objects
Inspect seat upholstery, covers, and cushion condition; remove aftermarket covers if present
Visually inspect connector(s) and wiring under the seat for damage, corrosion, or unsecured routing
Verify battery voltage and charging system are within spec before diagnosing airbag circuits

Signal parameters

Reference/supply voltage to OCS module: typically ~5 V reference for sensor electronics or 9–12 V supply for seat module — verify against manufacturer spec
Sensor signal: varied voltage or data packet on dedicated line/CAN; expected steady valid values when seat empty vs occupied — compare live data values to known-good or spec
Ground: good continuity to vehicle chassis ground (
Mat/element resistance: sensor mat elements usually measure as specific resistances or impedance ranges — check against service data
Communication: occupant classification module should appear on CAN/bus or LIN (if used); check for valid frames and no bus errors

Diagnostic algorithm

Read and record all related DTCs and freeze-frame data. Note ignition state, battery voltage, and when code set.
Visually inspect passenger seat, upholstery, and underside for moisture, damage, or aftermarket covers. Remove covers that could affect sensor.
Inspect connectors under the seat: unplug and inspect pins for corrosion, bent pins, or pushed-out terminals. Reconnect securely.
With scan tool, view live OCS/passenger seat data. Compare empty-seat vs occupant responses. Note abnormal or no-change values.
With ignition ON (engine off), backprobe the sensor/module connector: verify reference voltage, signal voltage, and ground presence. Compare to expected ranges.
Check continuity of harness between the sensor and the airbag/seat module; wiggle wiring while watching live data for intermittent faults.
Measure resistance or impedance of the sensor mat per manufacturer procedure. Replace sensor mat/module if out of spec.
Inspect for and remove any moisture; dry and retest. Replace seat cushion or module if water damaged.
If wiring and sensor check good, check seat control module/BCM communications and power/ground. Reflash or replace module only after verifying wiring and sensor.
After repair, clear codes and perform any required OCS recalibration or occupant classification learn procedure per manufacturer. Verify code does not return and airbag/passenger status is correct.

Likely causes

Connector loose, corroded, or pins pushed out at passenger seat sensor
Broken or damaged harness (pinched under seat, chafed at seat rail)
Failed occupant classification sensor mat/module
Moisture or liquid spilled into seat causing short or changed impedance
Aftermarket seat cover or cushion interfering with sensor readings

Fault status

⚠️ Status

Occupant Classification Sensor Circuit Fault (Passenger Seat) — airbag system has detected a fault in the passenger seat occupant detection circuit. Passenger airbag may be disabled and the airbag warning lamp will be lit.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours