P2197 The upstream oxygen or air-fuel sensor on bank 2 is stuck reading lean, or its signal does not make sense

O2 sensor signal stuck lean, bank 2 sensor 1

P2197 in short

P2197 means the bank 2 upstream oxygen or air-fuel sensor reads stuck lean or implausible. The sensor, wiring, an exhaust or vacuum leak, or a dirty or failing MAF can cause it. The car usually runs, but get it checked soon, and stop if it stalls or the check engine light flashes.

The upstream sensor sits in the exhaust before the catalytic converter and tells the computer how much oxygen is left after combustion. Bank 2 is the side of the engine without cylinder 1.

P2197 sets when that signal stays on the lean side or does not behave plausibly. That can be a real lean condition, such as a vacuum or exhaust leak, or a sensor or wiring fault. Toyota's bulletin ties it to incorrect air-fuel sensor response on some models, and Ford has bulletins on Transit water entry and 3.5L turbo engines.

It usually appears with P2195 (the bank 1 version) or with lean codes P0171 and P0174.

Most likely causes

  1. Failing bank 2 air-fuel or oxygen sensor

    Common general cause
    Why it ranks here
    TroubleCodes.net lists the sensor first; Toyota's bulletin names incorrect air-fuel sensor response, and a Toyota owner was told it was the bank 2 sensor.
    What would change this
    Likelier if live data shows the sensor flat or lean while fuel trims are near zero.
    How to test the oxygen (o2) sensor

  2. Vacuum leak or unmetered air

    Supported by vehicle data
    Why it ranks here
    TroubleCodes.net lists a large vacuum leak; an Edge owner reports P2195/P2197 with a brake booster air leak and a stall.
    What would change this
    Likelier with hissing, a high idle, positive fuel trims or a hard brake pedal.
    How to test the vacuum hoses and intake leaks

  3. Exhaust leak, damaged wiring or connector

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists exhaust leaks and damaged wiring; neither is tied to a vehicle in the bulletins I read.
    What would change this
    Likelier if there is exhaust noise before the sensor or the sensor harness is damaged.

  4. Water entering the engine bay (Transit)

    Supported by vehicle data
    Why it ranks here
    Ford's Transit bulletin lists P2197 among codes that may be due to water entry; unverified bulletin.
    What would change this
    Only for a 2015-2018 Transit with starting or misfire concerns after wet weather or washing.

What to test first

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

  1. Read all codes and freeze frame; note P2195, P0171, P0174 or MAF codes stored with P2197

    Low riskTool: OBD-II scan tool

  2. Warm the engine and watch the bank 2 upstream sensor and long-term fuel trim at idle and 2,500 rpm

    Low riskTool: Scan tool with live data

Symptoms

  • Check engine light
  • Poor performance
  • Reduced fuel economy
  • Stalling at a stop Gets more serious: stop and have it checked.
  • Flashing check engine light Gets more serious: stop and have it checked.

Compare with: Rough idle with the check engine light on

How to fix

  1. Listen for a hiss at idle and check that vacuum hoses and the brake booster hose are attached and not cracked.

Parts and cost context

  • Oxygen (O2) sensor:Confirm a real lean condition is ruled out before buying a sensor. 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

Toyota

  • 2009 · Sienna

    Supported by vehicle data

    Toyota's bulletin names P2197 with P0138/P0158 and incorrect A/F sensor response. Not verified as current.

  • 2007 · Avalon

    Supported by vehicle data

    One owner was told P2197 means a faulty bank 2 sensor and cites a Toyota bulletin.

  • T-SB-0001-10 RevStatus unverified

    A/F sensor response: P0138/P0158 with P2195 or P2197

    2005–2010avalon, camry, highlander, rav4, sienna, venza · issued · NHTSA 10132202

    P0138 and/or P0158 with P2195 or P2197 (A/F sensor signal stuck lean) may be due to incorrect air-fuel ratio sensor response; follow the diagnostic and repair procedure.

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

Honda

  • 604Status unverified

    LAF signal stuck lean, P2195 or P2197, V6

    2003–2004accord · issued · NHTSA 10014139

    Diagnostic trouble code P2195 or P2197, LAF signal stuck lean, V6 only; cause not stated in the summary.

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

Ford

  • TSB 18-2321Status unverified

    Transit drivability concerns from water entry

    2015–2018transit · issued · NHTSA 10148711

    Hard starting, misfires and MIL with P2195 to P2198 and others may be due to water entry over powertrain components.

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

  • TSB17-2124Status unverified

    MIL with P2195, P2197, P2626, P2629, 3.5L GTDI

    2015–2017explorer, f-150 · issued · NHTSA 10115945

    MIL with P2195, P2197, P2626 and/or P2629 on 3.5L GTDI Explorer and F-150; follow the service procedure.

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

  • P2195The upstream oxygen or air-fuel sensor on bank 1 reports a mixture that looks stuck lean or not believable

    Other bank Supported by vehicle data

    P2195 is the same fault on bank 1; Toyota and Honda bulletins list the pair together.

  • P0174Engine computer has reached its limit adding fuel on bank 2: the mixture is lean

    Shares causes Supported by vehicle data

    Toyota and Lexus bulletins list P0174 (bank 2 lean) with P2195 and P2197.

  • P0171Engine computer has reached its limit adding fuel on bank 1: the mixture is lean

    Shares causes Supported by vehicle data

    Toyota and Lexus bulletins list P0171 with P2195 and P2197.

All Oxygen sensors codes

Sources and review

  1. P2197 Code Definition and Details — TroubleCodes.net
  2. NHTSA complaint 11703726: 2013 Ford Edge — NHTSA (owner complaint)
  3. Toyota T-SB-0001-10: P0138/P0158 with P2195 or P2197 (A/F sensor signal stuck lean) — Toyota Motor Sales / NHTSA
  4. NHTSA complaint 10504491: 2007 Toyota Avalon — NHTSA (owner complaint)
  5. Ford TSB 18-2321: Transit drivability concerns from water entry — Ford Motor Company / NHTSA
  6. Toyota/Lexus 018-05: MIL on, P0171, P0174, P2195 or P2197 — Toyota Motor Sales (Lexus) / NHTSA
  7. Honda 604: DTC P2195 or P2197, LAF signal stuck lean, V6 only — American Honda / NHTSA
  8. Ford TSB 17-2124: MIL with P2195, P2197, P2626 and/or P2629, 3.5L GTDI — Ford Motor Company / NHTSA
Last reviewed
Written by
Saurabh K.
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