P2A00 Front air-fuel sensor signal out of range (bank 1, sensor 1)

O2 sensor range/performance, bank 1 sensor 1

Severity not verified — if the car runs badly, have it inspected

Sources describe the check engine light and sometimes erratic idle or power loss, but none rates how safe the car is to drive with this code.

It gets more serious if:

  • Inspect soon: Inspect soon if idle is erratic or power is lost, which TroubleCodes.net lists as possible.

Source: how we rate severity

P2A00 in short

P2A00 means the computer sees an implausible signal from the front oxygen or air-fuel sensor on bank 1. Wiring faults, a failed sensor, an exhaust leak or too much fuel pressure can cause it. Repeated sensor swaps did not cure it on one Nissan, so test before buying parts.

The front sensor reports the exhaust mixture so the computer can trim fuel. P2A00 is set when its signal is abnormal, erratic or implausible for the conditions.

TroubleCodes.net lists wiring faults, a defective sensor, exhaust leaks that contaminate reference air, excess fuel pressure and rarely the computer.

The code appears in bulletins for Ram diesels (sooting), GM trucks (intake leaks), Ford 6.7L diesels and Infiniti. A 2009 Versa owner had the sensor replaced three times with the code returning.

Most likely causes

  1. Front oxygen or air-fuel sensor failed

    Common general cause
    Why it ranks here
    TroubleCodes.net lists a defective sensor. A Versa dealer read "A/F sensor failed" but the code returned after three replacements, so it ranks with a caution.
    What would change this
    Rises if the circuit tests good and the sensor does not track. Falls if the code returns after a new sensor.
    How to test the oxygen (o2) sensor

  2. Damaged or corroded wiring or connector

    Common general cause
    Why it ranks here
    TroubleCodes.net lists wiring and connector faults first.
    What would change this
    Rises if damage is found. Falls if wiring tests good.

  3. Intake manifold or exhaust leak

    Supported by vehicle data
    Why it ranks here
    GM bulletin 22-NA-128 tests the intake manifold for leaks that set P2A00 on 2022 to 2024 trucks and SUVs; TroubleCodes.net lists exhaust leaks.
    What would change this
    Rises if a leak test fails. Falls otherwise.

  4. Diesel sooting contaminating the sensor (Ram 2007-2011)

    Supported by vehicle data
    Why it ranks here
    Chrysler bulletin 25-001-13 covers P2A00 on 2007 to 2011 Ram 2500/3500 diesels; it has dealers inspect and clean or replace the sensors after checking sooting bulletins. Summary only.
    What would change this
    Rises on a covered Ram diesel. Falls on gasoline cars.

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 data; note fuel pressure, lean or rich codes.

    Low riskTool: OBD-II scan tool

  2. With the exhaust cool, inspect the sensor wiring and connector and check exhaust and intake for leaks.

    Use caution

    Warning:The exhaust gets very hot. Let it cool fully first.

  3. Watch the sensor with a scan tool and ask a dealer whether a bulletin applies.

    Best left to a shopTool: scan tool with live data

    Warning:Needs a professional shop with the right scan tool and wiring diagrams; do not guess at this step.

Symptoms

  • Check engine light on
  • Higher fuel use
  • Erratic idle or power loss in some reports Gets more serious: stop and have it checked.

How to fix

  1. With the exhaust cool, look for a loose or damaged oxygen sensor plug.

Parts and cost context

  • Oxygen (O2) sensor:A Nissan owner replaced the sensor three times; check wiring and leaks first. Labor 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

Nissan

  • 2009 · Versa

    Possible — needs testing

    One owner reports P2A00 "A/F sensor failed" at seven dealer visits; the sensor was replaced three times and the code returned.

Dodge

  • 2007–2011 · Ram

    Supported by vehicle data

    Chrysler bulletin 25-001-13 covers P2A00 with P2000/P2A01 on diesel Ram 2500 pickup/3500. Whether still current is not verified.

  • 25-001-13 Rev. AStatus unverified

    MIL due to P2000, P2A00 and/or P2A01, front O2 sensor

    2007–2011ram · NHTSA 10188671

    Dealers check sooting bulletins and inspect and clean or replace the sensors. NHTSA summary only.

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

  • P0133Upstream oxygen sensor on bank 1 reacts too slowly

    Shares causes Possible — needs testing

    Ford bulletin 15-0042 and Infiniti bulletin ITB11054A list P2A00 alongside P0133 and other front-sensor codes.

All Oxygen sensors codes

P2A00 questions

Will a new sensor fix P2A00?

Not always. One Versa kept the code after three new sensors, so check wiring and leaks first.

Sources and review

  1. P2A00 O2 sensor circuit range/performance, bank 1 sensor 1 — TroubleCodes.net
  2. NHTSA complaint ODI 10522972, 2009 Nissan Versa: dealer read P2A00 A/F sensor failed on seven visits; sensor replaced three times — NHTSA
  3. General Motors bulletin 22-NA-128: test intake manifold for leaks causing MIL with P0172, P026D, P2459 and/or P2A00 — General Motors
  4. Chrysler bulletin 25-001-13 Rev. A: MIL due to P2000, P2A00 and/or P2A01, front O2 sensor, 2007-2011 Ram 2500/3500 diesel — Chrysler
  5. Nissan bulletin ITB11054A: Infiniti ECM codes P0031/P0051, P0032/P0052, P0130/P0150, P0133/P0153, P2A00/P2A03 — Nissan
Last reviewed
Written by
Saurabh K.
Editorial review
Pending
Technician review
Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

My Car

Pick your car and code pages will point out notes and bulletins for it. Saved only in this browser.

Fill this in from your VIN

Used once to identify your engine; not stored.