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Searching for your parts in the DENSO part catalog is easy. Simply select the type of part you are looking for along with the year/make/model of your U.S. or Canadian vehicle. For vehicles in Latin America, please go here.


    Search for cross reference part numbers for other manufacturers of the parts you're looking for.

    Cross Reference information is provided as a guide only. Please refer to the "Applications" lookup tabs for more detail. Materials and designs will differ among brands, so plugs are not exactly alike. Always check with your OE service manual for proper installation and settings.

    System Diagnosis

    Proper vehicle diagnosis requires a plan before you start

    Following a set procedure to base your troubleshooting on will help you find the root cause of a problem and prevent unnecessary repeat repairs.

    STEP ONE: Understand the Customer’s Concern

    • Information collection beyond the basics.
    • Questions asked MUST be related To the system you will be working on and the customer complaint.

    STEP TWO: Check for Technical Service Bulletins

    • Every vehicle that comes into the shop for a repair (not necessary for routine maintenance) should be checked for TSB’s, This can save you hours of troubleshooting.

    STEP THREE: Conduct a Systematic Diagnosis
    This step will be different for every system

    • Follow the troubleshooting steps for the system you are working on.
    • Make sure to check EVERY component of the system and that they are in proper working order.
    • Document your diagnosis including tests and results.

    STEP FOUR: Complete and Confirm the Repair

    • Make sure you have taken care of the customer’s concerns.
    • Try to duplicate the conditions that were present when the vehicle failed.


    O2 Sensor VS Air Fuel Ratio Sensor

    Oxygen Sensor bases have many holes

    Air/Fuel Sensor bases have fewer holes

    Here’s where you find the sensor type on the Vehicle:

    This label shows HO2S (or O2S)

    This label shows A/FS*

    Sensor Location

    #1 Cylinder is the key to locating the Oxygen Sensor

    To locate bank one / sensor one, the key is to identify the # 1 engine cylinder.

    In a V-type motor, sensor one (s) are in the exhaust system before the catalytic converter.

    In an inline motor, the rear sensor (or sensor two) is in the exhaust system after the catalytic converter

    O2 Sensor

    Check the voltage signal

    Using a 10-megaohm digital voltmeter Hook up the voltmeter’s red probe to the sensor’s signal wire and the black probe to engine ground. (use back probe method, DO NOT pierce the wire)

    1. Start the engine and let it idle for about two minutes while watching the digital reading on the voltmeter.
      • It should be fixed for a short period at around 0.1 or 0.2 volts.
    2. After two or three minutes, the voltage reading will begin to fluctuate between 0.1 and 0.9 volts.
      • If the sensor takes four minutes or more to begin fluctuating, replace it.
    3. Record the lowest and highest voltage reading from the voltmeter in any one-minute period.
      • The voltage should fluctuate constantly between 0.1 and 0.9 volts.
    4. Replace the oxygen sensor if the voltage:
      • Goes above this range,
      • Remains below 0.5 volts
      • Stays fixed at a particular voltage
    5. Open and close the engine throttle with a quick motion.
      • The sensor’s output voltage should go up and down accordingly

    Data Interpretation

    O2 Sensor voltage

    The O2 sensor normally alternates between 0 V and 1 V. When the value is fixed (stuck) at either 1 V or 0 V, investigate the cause of richness or leanness.

    Fixed at 1V Fixed at 0V
    Inspect weather something is causing a rich air-fuel ratio (see list below) If there are no abnormalities found replace the O2 sensor Inspect weather something is causing a lean air-fuel ratio (see list below) If there are no abnormalities found replace the O2 sensor

    Possible causes of a Rich Condition

    Possible causes of a Lean Condition

    Plugged air filter
    Faulty air mass meter
    Faulty idle control valve
    Faulty fuel injectors
    Fouled spark plugs
    Ignition timing
    Faulty air fuel sensor
    Associated wiring

    Faulty ECU
    Faulty MAP sensor
    Faulty fuel pressure regulator
    Restricted fuel return line
    Faulty ignition wires
    Faulty oxygen sensor
    Faulty EVAP
    Engine coolant temperature

    Possible causes of a Lean Condition

    Vacuum leak
    Faulty air mass meter
    Faulty MAP sensor
    Faulty fuel pressure regulator
    Restricted fuel filter
    Faulty PCV
    Exhaust gas leak
    Faulty air fuel sensor
    EGR valve

    Faulty ECU
    Faulty air flow meter
    Faulty idle control valve
    Faulty fuel pump
    Faulty fuel injectors
    Associated wiring
    Faulty oxygen sensor
    Ignition timing