B2650

Code

Generic B — Body

Occupant Classification System (OCS) Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 16 RU: 11

AI status

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Page language: EN

Causes

Damaged or disconnected connector at the occupant sensor/seat module
Broken, pinched, chafed, or shorted wiring in the seat harness (common where harness passes under seat)
Faulty occupant classification sensor mat or sensor module
Corrosion, water intrusion, or contamination in seat area or connectors
Poor or missing ground or reference voltage to the sensor
Faulty airbag/occupant classification control module or related ECU

Symptoms

SRS / airbag warning lamp ON
Passenger airbag status indicator (ON/OFF) incorrect or unavailable
Passenger airbag disabled or not deploying per normal logic
DTC B2650 stored in airbag/OCS control module; may be intermittent
Possible inability to complete vehicle self-test or to power cycle without code returning

What to check

Read and record stored codes, freeze frame and lamp status with a capable scan tool
Visually inspect passenger seat, underside, and all connectors for damage, corrosion, contamination or water
Check for recent work on seat (reupholstery, replacement, sensors disturbed)
Perform a wiggle test of seat harness/connectors while watching live data for the OCS sensor
Verify battery voltage and perform recommended SRS power-down procedure before working on airbags
Inspect grounds and power/reference supply to the OCS sensor/module

Signal parameters

Reference voltage commonly 5 V (check OEM spec); sensor signal typically varies with occupancy
Power supply to sensor may be switched 12 V or fused feed—verify per vehicle data
Signal line expected to change value with occupant presence (voltage or resistance change)
Ground continuity: near 0 ohms to chassis ground
Communication may be on LIN/CAN or a dedicated analog signal depending on vehicle; compare live-data values to OEM expected ranges

Diagnostic algorithm

Use a scan tool to read SRS/OCS live data and confirm B2650 is current or historic; record freeze-frame data.
Disable battery power and wait required time per manufacturer before accessing airbag/seat components.
Visually inspect the seat cushion area, connectors under the seat, and the occupant sensor mat for obvious damage, water, or contaminants.
Reconnect and reseat all related connectors; clean contacts if corroded. Ensure connector latches are fully engaged.
With battery reconnected and scan tool monitoring OCS data, perform a wiggle test of the seat wiring and connectors to look for intermittent changes or return of the code.
Measure reference voltage, signal voltage and ground at the sensor connector using a DMM and compare to manufacturer specifications.
Check continuity between the sensor connector and the airbag/OCS control module. Repair any open/shorted wiring found (insulate, replace harness sections, repair terminals).
If wiring and connectors test normal, measure sensor mat resistance or sensor output per service manual; replace the occupant classification sensor/mat if out of spec.
If sensor and wiring are good, verify module operation and communications; consider replacement or reprogramming of the OCS/airbag control module only after confirming wiring/sensor faults are not present.
Clear codes, cycle ignition and retest. Confirm SRS lamp extinguishes and passenger airbag status behaves correctly. Road/test as required.

Likely causes

Loose or corroded connector under the passenger seat
Damaged wiring caused by seat movement or abrasion
Failed occupant classification mat/sensor module
Intermittent connector contact from contamination or moisture

Fault status

⚠️ Status

Occupant Classification System sensor circuit malfunction detected. Passenger presence sensor signal out of expected range — inspect seat sensor, wiring, and connectors.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 2.5 hours

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