B1A26

Code

Generic B — Body

Occupant classification sensor fault — front passenger seat

Brand: Generic

Type: B — Body

Views: UK: 8 EN: 22 RU: 14

AI status

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Page language: EN

Causes

Damaged or disconnected occupant classification sensor (seat mat)
Damaged wiring harness, chafing, or connector corrosion between sensor and SRS/seat module
Short or open in sensor power, ground, or signal circuit
Faulty passenger seat module or SRS control module input circuit
Water/moisture intrusion in the seat or connector
Recent seat removal/installation, improper reconnection, or missing calibration/relearn

Symptoms

Passenger airbag status may show 'off' or incorrectly enabled/disabled
SRS warning light illuminated on instrument cluster
Possible inability to enable passenger airbag even with an occupant present
Diagnostic trouble code stored in SRS/airbag system (B1A26)
Intermittent airbag status changes when passenger shifts position or when seat is moved

What to check

Record freeze frame and DTC history with a capable scan tool
Confirm whether code is current, intermittent, or historic
Visually inspect passenger seat for signs of damage, water/moisture, or aftermarket seat covers that may affect the sensor
Inspect connectors under the seat and at the seat module: ensure fully seated, locked, and free of corrosion
Check wiring along seat rails for chafing, pinching, or broken conductors
Verify SRS system has required battery disconnect wait time and follow manufacturer safety procedures before service

Signal parameters

Occupant classification sensor resistance values or sensor pad open/short status (manufacturer-specific expected range)
Sensor supply voltage (typically 5 V or vehicle-specific reference) and ground integrity
Signal voltage or data packet on seat module bus (LIN/CAN) if applicable
SRS control module input status bits for passenger seat occupied/unoccupied
Diagnostic tool live data: occupant weight or classification value, sensor error flags

Diagnostic algorithm

Follow all SRS safety procedures before beginning (disconnect battery per manufacturer instructions and wait specified time)
Connect a diagnostic scan tool that can read SRS/occupant classification live data and freeze frame
Confirm B1A26 is present and note whether it is current or intermittent; check for related SRS codes
Perform a visual inspection of the passenger seat: upholstery, seat cushion, and underside for moisture or physical damage
Inspect connectors under the seat and at the seat module; disconnect and inspect pins for corrosion, bent pins, or pushed-out terminals; reconnect securely
With battery reconnected per safety procedure, monitor live data while a known weight is placed on the seat (use a test weight or occupant) and while moving the seat to reproduce the fault
If live data shows open/short or out-of-range resistance: measure continuity and resistance of sensor pad circuits to ground and supply with a multimeter (compare to expected ranges in service manual)
Check power and ground at the occupant sensor connector—verify proper reference voltage (typically 5 V) and good ground
If wiring and connectors are good but sensor outputs are invalid, consider replacing the occupant classification sensor/pad or seat module as dictated by manufacturer diagnostics
After repair or replacement, perform any required OCS calibration / occupant detection recalibration or SRS module relearn procedure; clear codes and test for reoccurrence
If intermittent and not reproducible, perform wiggle tests on harness while monitoring live data to find intermittent open/short
If communication messages for the seat module are missing on CAN/LIN, follow network diagnostics for the bus and SRS control module

Likely causes

Broken or pinched sensor pad cable under seat upholstery
Connector pins pushed out, bent, or corroded at the seat ECU/occupant sensor connector
Seat harness damaged by seat rail movement
Sensor module failure (internal electronics)
Moisture penetration in seat cushion sensor area

Fault status

⚠️ Status

Occupant classification sensor fault — front passenger seat. Sensor reporting invalid/open/short or communication failure; may disable or misreport passenger airbag status.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours