B2012

Code

Generic B — Body

Occupant Classification System Sensor Fault

Brand: Generic

Type: B — Body

Views: UK: 0 EN: 4 RU: 0

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty occupant classification (seat weight/position) sensor module
Damaged or corroded connector or wiring between sensor and SRS control module
Open or short in sensor signal, reference, or ground circuit
Poor or intermittent seat module grounding or power supply
Software or calibration fault in SRS/OCS control module
Recent seat removal, repair, or aftermarket seat cover/interference

Symptoms

Illuminated SRS / Airbag warning light on dash
Passenger airbag status lamp showing airbag disabled or 'OFF' for no clear reason
Occupant detection/seat-occupied indicator reports incorrect status
Possible steering/SRS system entering a fault/reduced functionality mode
Related diagnostic trouble codes stored in SRS control module

What to check

Read and record all SRS/airbag codes and freeze frame data with a capable scan tool
Check for other related B- or U-codes that indicate network or module communication faults
Visual inspection of connector(s) and wiring under the passenger seat for damage, corrosion, or moisture
Verify seat is correctly mounted and no foreign objects are trapped under the seat
Confirm whether any recent seat work, recall, or software update applies

Signal parameters

Reference power typically 5 V (module-specific) present at sensor connector when ignition on
Sensor output may be analog voltage, frequency, or digital CAN/serial message (varies by manufacturer)
Expected sensor output changes with applied load; nominal value ranges are manufacturer-specific
Continuity to ground from sensor ground pin should measure near 0 Ω (low resistance)
CAN network: occupant classification data messages present on vehicle CAN bus with regular update rate (typically 10–100 ms)

Diagnostic algorithm

Safely disable SRS per manufacturer procedure (battery disconnect and recommended wait) before seat removal or connector work.
Use an OEM-capable scan tool to confirm code B2012, capture freeze frame and any related SRS codes, then clear and re-check to see if code returns.
Perform a detailed visual inspection of the passenger seat area: connectors, wiring harness (especially under the seat), sensor module, and seat track for damage or foreign objects.
With ignition on and following safety procedures, backprobe the sensor connector and verify reference voltage, sensor output, and ground presence. Compare readings to manufacturer specs; look for opens/shorts or no reference voltage.
Wiggle test wiring and connectors while monitoring live sensor data to reproduce intermittent faults.
Check continuity/resistance of sensor harness between the sensor connector and SRS module connector (check for high resistance or opens).
Inspect and, if necessary, repair any damaged wiring, pins or connector terminals (replace corroded connectors).
If wiring and power/ground are good, verify proper communication messages on the CAN bus (if applicable) and ensure SRS module software/calibration is up to date. Recalibrate the OCS/sensor per manufacturer procedure if required.
If sensor still fails known-good signals and wiring, replace the occupant classification sensor/module only with OEM-specified part and perform required calibration/initialization.
Clear codes, perform self-tests and verify system operation (SRS lamp extinguished, correct passenger airbag status and sensor live data).

Likely causes

Connector pin corrosion or loose terminal at the sensor or SRS module
Damaged wiring harness under the seat (chafed, cut, or shorted)
Failed load cell/pressure sensor inside the seat module
Incomplete or lost sensor calibration after service
Moisture ingress in the sensor or connector

Fault status

⚠️ Status

Occupant Classification System sensor fault detected by the SRS control module. The passenger seat occupant sensor is reporting invalid or out-of-range data, or its circuit has an electrical problem. This may disable the passenger airbag or require sensor replacement/repair.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2 hours