B28F0

Code

Generic B — Body

Front Passenger Occupant Detection System Fault

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 14 RU: 15

AI status

Completed

ready

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Page language: EN

Causes

Faulty passenger seat occupancy/pressure sensor mat
Damaged, corroded or loose connector under passenger seat
Broken or shorted wiring harness (open, short to ground or power)
Seat heater or aftermarket accessories interfering with sensors
Occupant classification module (OCM) or airbag ECU/software fault
Water/moisture intrusion into seat or connector

Symptoms

Airbag warning lamp illuminated or stays on
Passenger airbag status incorrect on dash (airbag ON when seat empty or OFF when occupied)
Passenger occupant classification message displayed
Inability to enable/disable passenger airbag as expected
Related safety restraints behaving inconsistently (seatbelt reminder)

What to check

Read and record all stored DTCs and freeze frame data with a capable scanner
Check live data for passenger occupancy/classification status and sensor signal values
Visually inspect passenger seat area: connectors, clips, sensor mat, seat heater and wiring for damage or moisture
With ignition off, disconnect and reconnect the occupant sensor connector(s) to ensure good contact; inspect pins for corrosion or bent terminals
Perform a wiggle test on harness and connectors while monitoring live data for intermittent changes
Measure continuity and resistance of occupancy mat circuits per vehicle service manual

Signal parameters

Sensor reference voltage: typically a regulated reference (commonly ~5 V) provided by the module — verify per OEM specification
Signal voltage: occupancy/classification sensor output will vary (0–5 V range) depending on sensor type — see service manual for expected values
Resistance/impedance of sensor mat: varies by design — many mats read kilo-ohms to mega-ohms when unoccupied vs different when occupied; check manufacturer table
Connector pin continuity/Ground: near 0 ohms for ground circuits; expect low ohms for power and reliable continuity for signal return
CAN/serial comms: module should show normal bus activity; loss of bus messages may indicate module or wiring fault

Diagnostic algorithm

Retrieve freeze frame and full DTC list; note history and whether fault is permanent or intermittent.
Inspect passenger seat area: remove seat trim as needed and visually inspect sensor mat, connectors, harness routing, seat heater and any signs of moisture or physical damage.
With a scan tool, monitor live occupancy/classification signals while a technician sits in different positions (no occupant, light object, adult) to observe expected changes.
Perform connector pin inspection: disconnect occupant sensor connector(s), inspect for bent pins, corrosion, water or foreign material; clean and apply dielectric grease if required.
Perform wiring checks: continuity to module and ground checks; check for short to battery/ground per wiring diagram. Repair any open/shorted wires.
Measure sensor reference and signal voltages and compare to OEM values. If voltages absent, follow power/ground supply path to find open/fuse/relay issue.
If wiring and connectors are good but sensor readings are out of spec, replace the passenger occupant sensor mat per procedure.
After any replacement or repair, clear codes and perform required occupant classification calibration or system initialization following manufacturer instructions.
If fault persists after sensor replacement and calibration, consider replacing/repairing the occupant classification module/airbag ECU and reprogramming as required. Escalate to dealer or specialist for module programming if necessary.

Likely causes

Loose or corroded connector under the passenger seat
Damaged sensor mat (wear, crushed wires, moisture)
Wiring harness abrasion or pinched wires under seat
Faulty occupant classification module or improper software/flash state

Fault status

⚠️ Status

Front Passenger Occupant Detection System Fault — airbag system may be disabled or incorrectly enabled; service required. Airbag warning indicator and passenger status message may be displayed.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours