B1650 Occupant detection/classification system malfunction (Subaru, Toyota)

Passenger occupant detection system (ODS/OCS) fault

B1650 in short

On Subaru and Toyota, B1650 means the front passenger seat's occupant detection (classification) system has found a fault, so the airbag light comes on and the passenger airbag may not be managed correctly. Subaru links it to the seat sensor mat, moisture and calibration. Have a dealer check it soon; never probe airbag wiring yourself.

The front passenger seat has a sensor in its cushion that tells the airbag computer whether the seat is empty or holds a child seat, a small person or an adult. Subaru calls this the occupant detection system (ODS); Toyota calls it the occupant classification system. B1650 is the code both use when that system reports a malfunction.

Subaru's bulletins diagnose B1650 together with B1760 (sensor mat abnormal) on 2014–2016 Foresters, and say liquid, rain or high humidity reaching the mat can set them. On 2010–2014 Legacy and Outback, Subaru gives a revised B1650 chart and an ODS rezeroing (calibration) procedure. Toyota's 2004 bulletin covers initializing the occupant classification system for B1150 and B1650.

Subaru also recalled 2015–2018 Foresters with heated seats because the sensor mat harness connection may loosen and turn the passenger airbag off. That recall does not name B1650, but a dealer can check whether it applies. Diagnosis and repair of the airbag system belong with a dealer or trained technician.

Pick your make

B1650 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Passenger seat occupant detection sensor mat or seat cushion faulty

    Supported by vehicle data
    Why it ranks here
    Subaru's 07-108-16R bulletin diagnoses B1650 with B1760 (sensor mat abnormal), and Forester owners report dealers replacing the passenger seat bottom for B1650; a Toyota dealer recommended a new seat sensor mat on a Tacoma.
    What would change this
    Rises if B1760 is stored with B1650 on a Subaru, or the dealer's test faults the mat. Falls if the code clears after the seat dries or after calibration.

  2. Liquid, rain or high humidity reaching the sensor mat

    Supported by vehicle data
    Why it ranks here
    Subaru's bulletin summary names liquid, rain or high humidity reaching the mat as a way these codes can set; Honda's manual also warns that spilled liquid can stop the passenger sensors working.
    What would change this
    Rises if the seat was wet or something was spilled before the light came on. Falls if the seat was dry.

  3. Occupant detection system needs rezeroing (calibration) or initialization

    Supported by vehicle data
    Why it ranks here
    Subaru's B1650 chart for Legacy and Outback includes an ODS rezeroing procedure, and Toyota's 2004 bulletin covers initializing the system for B1650.
    What would change this
    Rises after seat work or parts replacement. Falls if calibration was already done and the code returns.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Have the airbag codes read with a scan tool that can talk to the airbag module, and note every code stored.

    Low riskTool: scan tool with airbag (SRS) access

    • IfB1650 is stored with B1760 on a Subaru

      It meansSubaru diagnoses the two together and looks at the sensor mat.

      Go to step 2

    • IfB1650 is the only airbag code

      It meansThe occupant system itself reported the fault.

      Go to step 2

    • IfOther airbag codes are stored as well

      It meansA technician should work through them in the order the service manual gives.

      Go to step 4

  2. Give your VIN to the dealer and ask about Subaru bulletins 07-108-16R or 07-84-14R (or Toyota 00204) and open recalls such as Forester recall WUM-98.

    Low risk

    • IfA bulletin or recall covers the car

      It meansThe dealer follows that procedure.

      Go to step 4

    • IfNothing applies

      It meansRule out moisture or objects on the seat first.

      Go to step 3

  3. Remove anything on or under the passenger seat, dry any spilled liquid, and see whether the airbag light still comes on after the next restart.

    Low risk

  4. Have a dealer or trained technician run the airbag system diagnosis from the service manual.

    Best left to a shopTool: maker's diagnostic tool

    Warning:Never probe airbag connectors or wiring with a test light or meter, and never unplug them yourself. Nissan warns that airbags and pretensioners can still deploy after the ignition is off, and that test equipment must not be used on airbag circuits unless the service manual calls for it. Leave this to a dealer or trained technician.

Symptoms

  • Airbag warning light stays on after the engine starts
  • Passenger airbag status light shows the airbag off with an adult in the seat

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

  • Front passenger seat occupant detection sensor mat / seat cushion:On Subaru the mat is part of the seat cushion assembly. Check recalls and bulletins first. Replacement and calibration are dealer work. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Subaru

  • 2014–2016 · Forester

    Supported by vehicle data

    Subaru's bulletin covers B1650 with B1760 on these Foresters. Separately, recall WUM-98 (19V-701) replaces the sensor mat harness on 2015–2018 Foresters with heated seats; it does not name B1650, so ask the dealer to check it. Whether the bulletin is still current is not verified.

  • 2015–2018 · Forester

    Possible — needs testing

    Recall 19V-701 (WUM-98) for Foresters with heated seats: the passenger occupant sensor harness connection may loosen and switch the passenger airbag off. It does not name B1650, so treat it as something to check, not a confirmed cause.

  • 2010–2014 · Outback

    Supported by vehicle data

    Subaru's 07-84-14R gives a revised B1650 chart and ODS rezeroing. Whether it is still current is not verified.

  • 2010–2014 · Legacy

    Supported by vehicle data

    Subaru's 07-84-14R gives a revised B1650 chart and ODS rezeroing. Whether it is still current is not verified.

  • 07-108-16RStatus unverified

    ODS diagnosis for B1760 and/or B1650

    2014–2016forester · issued · NHTSA 10117531

    Diagnosis procedure for occupant detection system DTCs B1760 (sensor mat abnormal) and B1650 (occupant classification system malfunction).

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 07-84-14RStatus unverified

    ODS rezeroing and revised B1650 chart

    2010–2014legacy, outback · issued · NHTSA 10163000

    Clearer ODS rezeroing (calibration) steps and a revised diagnostic chart for B1650 (ODS failure).

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Toyota

  • 2004 · Highlander

    Supported by vehicle data

    Toyota's 2004 bulletin covers occupant classification system initialization for B1650. Whether it is still current is not verified.

  • 00204Status unverified

    Occupant classification system initialization

    2004highlander · issued · NHTSA 10009686

    Initializing the occupant classification system for DTCs B1150 and B1650.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • B1760Occupant detection system sensor mat abnormal (Subaru)

    Shares causes Supported by vehicle data

    Subaru diagnoses B1650 together with B1760 (sensor mat abnormal); both point at the passenger seat sensor mat.

All Airbags and seat-belt restraints (SRS) codes

B1650 questions

Is the passenger airbag working while B1650 is set?

Don't count on it. The light means the system has found a fault, and owner's manuals warn the airbags may not work properly until it is checked. Seat children in the back.

Can a wet seat cause B1650?

On Subaru, yes. Subaru's bulletin says liquid, rain or high humidity reaching the sensor mat can set B1650 and B1760. Dry the seat; if the light stays on, have it diagnosed.

Sources and review

  1. 2023 Accord Owner's Manual: Airbag System Indicators — American Honda Motor Co.
  2. Camry Owner's Manual (OM06291U) — Toyota
  3. Subaru 07-108-16R: ODS diagnosis for DTC B1760 (sensor mat abnormal) and/or B1650 (occupant classification system malfunction) — Subaru of America ,
  4. NHTSA complaint ODI 11265760 (2016 Subaru Forester) — NHTSA Office of Defects Investigation
  5. NHTSA complaint ODI 11184937 (2017 Subaru Forester) — NHTSA Office of Defects Investigation
  6. NHTSA complaint ODI 10607942 (2009 Toyota Tacoma) — NHTSA Office of Defects Investigation
  7. Subaru 07-84-14R: ODS rezeroing procedure and revised diagnostic chart for DTC B1650 (ODS failure) — Subaru of America ,
  8. Toyota 00204: occupant classification system initialization (DTC B1150 and B1650) — Toyota Motor Sales USA ,
  9. Recall 19V-701 (Subaru WUM-98): 2015-2018 Forester passenger occupant detection sensor harness — Subaru of America ,
  10. Nissan Supplemental Restraint Systems: damage analysis and repair using Diagnostic Trouble Codes (TechNews, Summer 2016) — Nissan North America ,
  11. NHTSA complaint ODI 11480238 (2017 Subaru Forester) — NHTSA Office of Defects Investigation
Last reviewed
Written by
Saurabh K.
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