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Home / DTC / B2951 — Occupant Classification Sensor Fault

B2951 — Occupant Classification Sensor Fault

Detailed page for trouble code B2951.

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B2951

Generic B — Body

Occupant Classification Sensor Fault

Brand: Generic
Type: B — Body
Views: UK: 0 EN: 2 RU: 0
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Page language: EN

Causes

  • Damaged or corroded connector or wiring in the seat harness
  • Open, short or high resistance in sensor mat circuits
  • Faulty occupant classification sensor module or mat
  • Poor ground or missing reference voltage to the sensor
  • Water intrusion, contamination, or mechanical damage to the sensor mat
  • Incorrect or lost sensor calibration (software/ECU issue)

Symptoms

  • Airbag / SRS warning lamp illuminated
  • Passenger airbag status message (airbag disabled/enabled incorrectly)
  • Driver/passenger seat occupant detection incorrect or unavailable
  • Diagnostic trouble code B2951 stored in SRS module
  • Possible chimes or dashboard messages related to passenger airbag

What to check

  • Use a scan tool to read all SRS codes and freeze-frame data
  • Visually inspect passenger seat, upholstery, connectors and harness for damage or contamination
  • Check for any Service Bulletins or calibration procedures for occupant classification
  • Verify connector pin integrity and presence of locking tabs
  • Measure reference voltage and ground at sensor connector with key ON (typically 5V reference and sensor ground)
  • Perform wiggle test on seat harness while monitoring scan tool for code changes

Signal parameters

  • Reference voltage typically ~5 V at the sensor supply pin (varies by manufacturer)
  • Sensor ground should be near 0 V with low resistance to chassis ground
  • Signal output varies with occupancy (often a voltage or CAN/serial data representing weight or sensor zone values)
  • Open circuit (infinite resistance) or short to ground/power on sensor lines indicates a fault
  • Scan tool may display raw weight/zone values (e.g., 0–255 counts or kilograms) — unexpected or frozen values indicate a problem

Diagnostic algorithm

  1. Connect a capable scan tool, record all stored SRS codes and freeze-frame data; note if other SRS or communication codes are present.
  2. Visually inspect the passenger seat area for signs of water, debris, or damage; remove seat cushion trim if necessary to access mat and connectors.
  3. Disconnect battery per manufacturer safety procedure before disconnecting any SRS connectors; then inspect and reseat the occupant sensor connector(s).
  4. With battery reconnected and ignition ON (follow safe SRS procedures), verify reference voltage and ground at the sensor connector pins. Compare to manufacturer spec.
  5. Measure continuity/resistance of sensor mat circuits and harness between connector and sensor module. Look for opens, high resistance, or intermittent connections (wiggle test).
  6. If the wiring and connectors test good, use the scan tool to view live occupant sensor values or run the sensor self-test. Attempt a recalibration/initialization if procedure is available.
  7. If sensor outputs are out of range or calibration fails, replace the occupant classification mat/module or repair the identified damaged wiring/connector.
  8. After repair or replacement, clear codes, perform required calibration/initialization, and verify that the SRS light stays off and that occupant detection behaves correctly.
  9. If fault persists and wiring/sensor are good, investigate SRS control module functionality and inter-module communications (CAN/UART) as a potential cause.

Likely causes

  • Connector pin corrosion or disconnected seat harness connector
  • Broken wire in seat harness (pinched at seat frame or recliner)
  • Failed sensor mat under seat cushion
  • Loss of 5V reference or ground to the sensor
  • Contamination (liquid, debris) causing mat short or open

Fault status

⚠️ Status
Occupant Classification Sensor Fault — The passenger seat occupant detection/weight sensor circuit or module is reporting a fault. Passenger airbag enable/disable may be affected; SRS/service airbag warning lamp will be illuminated.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

B2950 B2952 B1650 B1651 U0121 U0140
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