B3860

Code

Generic B — Body

Seat Occupancy Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 7 EN: 8 RU: 6

AI status

Completed

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Page language: EN

Causes

Open or shorted wiring in the seat occupancy sensor circuit
Corroded, loose or damaged connector at the sensor or control module
Failed seat occupancy sensor mat or pressure sensor element
Faulty body/airbag control module or internal driver circuit
Water intrusion or contamination in the seat cushion
Recent seat repair, removal or replacement with improper reinstallation

Symptoms

Airbag warning or SRS light illuminated
Passenger airbag status may show OFF when occupied (or ON when empty)
Seatbelt reminder light/chime behavior incorrect
Possible DTC present even after ignition cycles
Intermittent or persistent fault without other drivability symptoms

What to check

Scan for stored/active DTCs and freeze frame data; note history and occurrence count
Visually inspect seat, seat cushion cover and underside for damage or moisture
Inspect connectors and harness routing at seat, underseat junctions and control module
Perform wiggle test on harness with scan tool connected to see fault set/reappear
Compare passenger airbag status on dash with actual occupancy
Check for recent collision, seat replacement or upholstery work

Signal parameters

Supply/reference voltage: typically 5 V or vehicle reference — should be present at sensor connector with ignition on
Signal voltage: depends on sensor type — typical occupant sensor outputs 0–5 V or variable resistance; should change smoothly with applied load
Expected idle/open-circuit: infinite/open (if circuit open) or near known resistance for mat sensors; short to ground or to battery will show near 0 V or battery voltage
Continuity: low resistance between sensor pins and module where wiring intact; open or high resistance indicates break
Intermittent: signal may fluctuate when pressure applied or when harness is flexed

Diagnostic algorithm

Read and record DTC(s) and freeze frame data. Check for related airbag/body codes.
Visually inspect seat cushion, sensor mat area and connectors for contamination, damage or improper seating.
With battery charged, backprobe connector at sensor and verify reference/supply voltage present (compare to vehicle spec).
Measure signal output while applying weight to the seat; look for smooth, repeatable change in voltage/resistance. If no change, suspect sensor or open circuit.
Check continuity and resistance of wiring between sensor connector and airbag/body control module; repair any opens or shorts. Perform wiggle test while monitoring signal/scan tool live data.
Inspect/repair connector pins and grounds; clean corrosion and ensure secure mating.
If wiring and connectors good but sensor output is out of range or inconsistent, replace the seat occupancy sensor/mat assembly.
If sensor and wiring test good but fault persists, inspect the body/airbag control module inputs and replace or reprogram only after confirming module fault with manufacturer procedures.
After repair, clear codes, perform diagnostic relearn procedures if required by manufacturer, and verify correct operation and no code return.

Likely causes

Connector pins pushed out, bent or corroded at the seat sensor
Broken/damaged harness where it flexes (seat rail area)
Sensor mat damaged by liquid, sharp object or heavy wear
Intermittent contact caused by foam compression or seat cover interference

Fault status

⚠️ Status

Seat Occupancy Sensor Circuit Malfunction detected. Occupant classification may be unreliable; airbag/passenger restraint behavior could be affected. Inspection and repair recommended before vehicle is returned to service.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours