B1861 Driver side knee airbag circuit open (Lexus)

Knee airbag squib circuit open, SRS light on

B1861 in short

On Lexus, B1861 means the airbag computer found an open circuit in the driver side knee airbag firing circuit. The SRS light comes on, and the knee airbag may not deploy. Lexus bulletins point to the instrument panel wire harness. Have a dealer check it soon, and ask about warranty coverage.

The airbag computer checks the knee airbag circuit at every startup. B1861 is stored when that circuit reads open, and the SRS light comes on.

Lexus bulletin LSB-0167-08, later replaced by L-SB-0007-19, covers 2006 to 2008 IS 250, IS 350 and IS F cars. For LS 460 and LS 600h models, LSB-0003-10 covers B1861 and/or B1866 with a replacement instrument panel wire harness.

A complaint quotes the repair as covered under the Lexus restraint system warranty. Coverage is not guaranteed, so ask a dealer.

Pick your make

B1861 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. Instrument panel wire harness

    Supported by vehicle data
    Why it ranks here
    Three Lexus bulletins cover B1861 and tell dealers to replace or repair the instrument panel harness, and a dealer readout quoted in an owner complaint matches.
    What would change this
    Rises on a 2006 to 2008 IS or a 2007 to 2009 LS. Falls if the harness checks good.

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

    • IfB1861 is stored on a Lexus

      It meansThe driver side knee airbag circuit reads open.

      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 3

  2. Give your VIN to the dealer and ask whether a service bulletin or warranty extension covers this code on your car.

    Low risk

    • IfA bulletin or extension applies

      It meansThe dealer repairs it under the bulletin.

      Go to step 3

    • IfNothing applies

      It meansThe circuit still needs a diagnosis.

      Go to step 3

  3. Leave the diagnosis to a dealer or trained technician, who measures the circuit with the service manual procedure.

    Best left to a shopTool: scan tool with airbag access, manufacturer procedure

    Warning:Airbag wiring can set off an airbag if it is probed, disconnected or powered the wrong way, and that can cause serious injury. Do not test or unplug airbag connectors yourself.

Symptoms

  • Airbag (SRS) warning light stays on after the engine starts

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

  • Instrument panel wire harness:Lexus has covered this under its restraint system warranty on some cars; ask before paying. 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

Lexus

  • 2006–2008 · IS

    Supported by vehicle data

    Lexus bulletins LSB-0167-08 and L-SB-0007-19 cover B1861 on the IS 250 and IS 350, and an owner reports the harness replacement under warranty. Whether they are still current is not verified.

  • LSB-0167-08Status unverified

    SRS light on with DTC B1861

    2006–2008is-250, is-350 · issued · NHTSA 10029031

    Lexus bulletin for an SRS light with B1861; superseded later by L-SB-0007-19.

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

  • L-SB-0007-19Status unverified

    Supersession notice for LSB-0167-08

    2006–2008is-250, is-350, is-f · issued · NHTSA 10155240

    Replaces LSB-0167-08 and adds the 2008 IS F; the summary does not give the repair.

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

  • LSB-0003-10Status unverified

    SRS light on with B1861 and/or B1866

    2007–2009ls-460, ls600h · issued · NHTSA 10033557

    Replace the instrument panel wire harness after confirming the condition matches.

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

No curated relationships for B1861 yet.

All Airbags and seat-belt restraints (SRS) codes

Sources and review

  1. 2023 Accord Owner's Manual: Airbag System Indicators — American Honda Motor Co.
  2. Camry Owner's Manual (OM06291U) — Toyota
  3. Lexus LSB-0167-08: vehicles may exhibit an SRS light on condition with DTC B1861 — Lexus ,
  4. Lexus L-SB-0007-19: supersedes LSB-0167-08, applicability now includes 2008 IS F — Lexus ,
  5. Lexus LSB-0003-10: SRS light on with DTC B1861 and/or B1866; replace the instrument panel wire harness (LS 460, LS 600h) — Lexus ,
  6. NHTSA complaint ODI 991144 (2006 Lexus IS 250) — NHTSA Office of Defects Investigation
Last reviewed
Written by
Saurabh K.
Editorial review
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