B2876

Code

Generic B — Body

Occupant classification sensor circuit range/performance

Brand: Generic

Type: B — Body

Views: UK: 6 EN: 9 RU: 4

AI status

Completed

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Page language: EN

Causes

Damaged or faulty occupant classification sensor (pressure/mat sensor)
Open, short or high-resistance in sensor harness or connector
Corroded or poorly seated connector or terminal
Poor ground or loss of reference voltage to the sensor
Water/moisture intrusion or foreign debris in the seat cushion/mat
Incorrect or aftermarket seat cover or repair changed sensor characteristics

Symptoms

Airbag warning lamp (SRS) illuminated on dash
Passenger airbag ON/OFF indicator behaves incorrectly or shows disabled when occupied
Occupant classification “passenger” status incorrect (airbag disabled/enabled unexpectedly)
Possible inability to complete seat/occupant sensor calibration
Diagnostic trouble codes stored for occupant classification or SRS

What to check

Record all stored codes and freeze frame data with a qualified scan tool
Review service history for recent seat or wiring repairs and for aftermarket seat covers
Visually inspect seat bottom, connectors, and harness for damage, corrosion, or moisture
Follow manufacturer SRS safety procedure before probing (battery disconnect and required wait time)
With SRS power safe, unplug and reseat connector(s) at sensor and at SRS/seat module; look for bent pins
Measure reference voltage and ground at the sensor connector with ignition ON (see signal parameters and vehicle manual)

Signal parameters

Reference voltage typically provided by SRS system — ~5 V reference (vehicle-specific; consult service manual)
Sensor output typically a low-voltage signal that changes with load (commonly 0.0–5.0 V range) or a variable resistance range (hundreds ohms to several kilo-ohms depending on design)
Open circuit = very high/OL resistance or no voltage signal; short to ground ≈ 0 V; short to supply ≈ reference voltage stuck or
Expected dynamic behavior: signal should change smoothly when weight is applied/removed; abrupt jumps, flatlines, or oscillation indicate fault; confirm exact numeric values from the vehicle’s service data

Diagnostic algorithm

Safety first: disable SRS per manufacturer procedure (battery disconnect and required waiting period) before accessing connectors or removing the seat.
Connect a factory-level scan tool, read DTC(s) and freeze frame data, note when the fault sets and related codes.
Inspect visually: remove seat trim as required, inspect occupant sensor mat, harness routing, connectors, and look for moisture, damage, or poor repairs.
With SRS disabled/secured per procedure, unplug and reseat connectors at the occupant sensor and SRS/seat module; check for corrosion or bent pins.
Restore power (keeping safety procedures), turn ignition to ON (engine off) and measure sensor reference voltage, ground, and signal at the connector against vehicle-specific values.
Apply known weights or have technician sit/unseat while monitoring live sensor data to verify signal changes; perform wiggle tests on harness to reproduce the fault if intermittent.
If the signal is out-of-range or open, isolate wiring: check continuity from sensor connector to SRS module, check for shorts to ground or battery, and repair wiring/connector faults.
If wiring and connectors are good but sensor output is incorrect, replace the occupant classification sensor (or seat module if applicable).
After repair or replacement, perform required initialization/calibration of the occupant classification system with a scan tool and follow reset procedures.
Clear DTCs, re-check for permanent/latent codes, and perform validation tests (occupant presence tests) to confirm the fault is resolved.
If fault persists after sensor and wiring replacement, consider diagnosis of SRS control module or software update/reflash by dealer-level tools.

Likely causes

Broken wire or pinched harness under the seat
Corroded connector at the sensor or ECU
Worn or punctured occupant sensing mat allowing moisture/shorts
Connector not fully engaged after seat removal/repair
Failed sensor element (resistance drift or intermittent open)

Fault status

⚠️ Status

Occupant classification sensor circuit range/performance — SRS module detected sensor output outside expected range or inconsistent with occupant classification limits.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 2.5 hours