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Home >> Toyota >> 2004 >> Highlander Limited, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Engine Control System (SFI) - Diagnostics (2AZ-FE)) >> DTC P2A00: A/F Sensor Circuit Slow Response (Bank1 Sensor 1) >> Inspection Procedure

Inspection Procedure

WARNING: This page is about a different variant/trim than selected.

It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble areas are malfunctioning or not.

  1. Connect the hand-held tester to the DLC3 on the vehicle.
  2. Turn the ignition switch ON.
  3. Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
  4. Enter the following menus: DIAGNOSIS/ENHANCED OBD II/ACTIVE TEST/A/F CONTROL.
  5. Perform the A/F CONTROL operation with the engine idle (press the right or left button).

    Result: 

    A/F sensor reacts in accordance with increase and decrease of injection volume: 

    +25 % --> RICH output: Less than 3.0 V 

    -12.5 % --> LEAN output: More than 3.35 V 

    Heated oxygen sensor reacts in accordance with increase and decrease of injection volume: 

    +25 % --> RICH output: More than 0.55 V 

    -12.5 % --> LEAN output: Less than 0.4 V 

    NOTE: The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about 20 seconds of delay at maximum.
    Fig 1: Active Test Result Chart
    G02908046Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    The following A/F CONTROL procedure enables a technician to check and graph the voltage outputs of both the A/F sensor and the heated oxygen sensor.

    For displaying the graph, enter "ACTIVE TEST/A/F CONTROL/USER DATA", select "AFS B1S1 and O2S B1S2" by pressing "YES" and push "ENTER". Then press "F4".

    HINT:

    • DTC P2A00 may be also detected, when the air fuel ratio is stuck rich or lean.
    • A low A/F sensor voltage could be caused by a RICH air-fuel mixture. Check for conditions that would cause the engine to run with a RICH air-fuel mixture.
    • A high A/F sensor voltage could be caused by a LEAN air-fuel mixture. Check for conditions that would cause the engine to run with a LEAN air-fuel mixture.
    • Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
  1. CHECK OTHER DTC OUTPUT (IN ADDITION TO A/F SENSOR DTC) 
    1. Read the DTC using the hand-held tester or the OBD II scan tool.

      Result: 

      DTC OUTPUT RESULT

      Display Proceed to
      Only P2A00 is output A
      P2A00 and other codes is output B

      HINT:

      If any other codes besides P2A00 is output, perform the troubleshoot on that DTC before.

    1. B: GO TO RELEVANT DTC CHART (See  DIAGNOSTIC TROUBLE CODE CHART  ) 
    2. A: GO TO NEXT STEP. 
  2. READ VALUE OF OBD II SCAN TOOL OR HAND-HELD TESTER (OUTPUT VOLTAGE OF A/F SENSOR) 
    1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
    2. Warm up the A/F sensor (bank 1 sensor 1) by running the engine at 2,500 rpm for approximately 90 seconds.
    3. Read the A/F sensor voltage output on the hand-held tester or OBD II scan tool.
    4. Hand-held tester only:

      On the hand-held tester, enter the following menus: DIAGNOSIS/ENHANCED OBD II/SNAPSHOT/MANUAL SNAPSHOT/USER DATA. Read the values.

    5. Select "AFS B1 S1/ENGINE SPD" and press YES.
    6. Monitor the A/F sensor voltage carefully.
    7. Check the A/F sensor voltage output under the following conditions:
      1. Allow the engine to idle for 30 seconds.
      2. Run the engine at approximately 2,500 rpm. Do not suddenly change the rpm.
      3. Raise the engine speed to 4,000 rpm and quickly release the accelerator pedal so that the throttle is fully closed.

      Standard: 

      Condition (1) and (2) 

      Voltage change of 3.3 V (0.66 V)* (between approximately 3.1 to 3.5 V) as shown in the illustration. 

      Condition (3) 

      A/F sensor voltage increases to 3.8 V (0.76 V)* or more when fuel is cut during engine deceleration as shown in the illustration. 

      *: Voltage when using the OBD II scan tool. 

      Fig 2: Engine RPM And A/F Sensor Voltage Normal And Malfunction Condition
      G02908047Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT:

      • Whenever the A/F sensor output voltage remains at approximately 3.3 V (0.660 V) on OBD II scan tool under any condition as well as the above conditions, the A/F sensor may have an open circuit. This will happen also when the A/F sensor heater has an open circuit.
      • Whenever the A/F sensor output voltage remains at a certain value of approximately 3.8 V (0.76 V) on OBD II scan tool or more, or 2.8 V (0.56 V) on OBD II scan tool or less under any condition as well as the above conditions, the A/F sensor may have a short circuit.
      • The ECM will stop fuel injection (fuel is cut) during engine deceleration. This will cause a LEAN condition and should result in a momentary increase in the A/F sensor output voltage.
      • The ECM must establish a closed throttle position learned value to perform fuel cut. If the battery terminal has been disconnected, the vehicle must be driven over 10 mph (16 km/h) to allow the ECM to learn the closed throttle position.
      • When the vehicle is driven:

        The output voltage of the A/F sensor may be below 2.8 V (0.76 V) on OBD II scan tool during fuel enrichment. For the vehicle, this translates to a sudden increase in speed with the accelerator pedal fully depressed when trying to overtake another vehicle. The A/F sensor is functioning normally.

      • The A/F sensor is a current output element, and therefore the current is converted into voltage inside the ECM. If measuring voltage at connectors of the A/F sensor or ECM, you will observe a constant voltage.
    1. OK: Go to step   14 . 
    2. NG: GO TO NEXT STEP. 
  3. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) 
    1. Disconnect the A6 A/F sensor connector.
    2. Measure the resistance of the A/F sensor terminals.
      Fig 3: Identifying Air Fuel Ratio Sensor Connector Terminals
      G02908048Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard: 

      TESTER CONNECTION AND CONDITION SPECIFICATIONS

      Tester Connection Condition Specified Condition
      1 (HT) - 2 (+B) 20°C (68°F) 1.8 to 3.4 Ω
      1 (HT) - 4 (AF-) - 10 kΩ or higher
    1. NG: REPLACE AIR FUEL RATIO SENSOR 
    2. OK: GO TO NEXT STEP. 
  4. INSPECT RELAY (EFI) 
    1. Remove the EFI relay from the engine room J/B.
    2. Measure the resistance of the EFI relay.
      Fig 4: Identifyiing EFI Relay Test Terminals
      G02908049Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard: 

      TESTER CONNECTION AND CONDITION SPECIFICATIONS

      Tester Connection Specified Condition
      3 - 5 10 kΩ or higher
      3 - 5 Below 1 Ω (when battery voltage is applied to terminals 1 and 2)
    1. NG: REPLACE RELAY 
    2. OK: GO TO NEXT STEP. 
  5. CHECK WIRE HARNESS (A/F SENSOR - ECM) 
    1. Check the wire harness between the ECM and A/F sensor.
      1. Disconnect the A6 A/F sensor connector.
      2. Disconnect the E8 ECM connector.
      3. Measure the resistance of the wire harness side connectors.
        4. Fig 5: Identifying A/F Sensor & ECM Connector Terminals
        G02908050Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard: 

      Fig 6: Harness Resistance Values
      G02908051Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      Fig 7: A/F Sensor And EFI Relay Circuit Diagram
      G02908052Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. NG: REPAIR OR REPLACE HARNESS AND CONNECTOR 
    2. OK: GO TO NEXT STEP. 
  6. CHECK AIR INDUCTION SYSTEM 
    1. Check for vacuum leaks in the air induction system.

      OK: There is no leak in the air induction system. 

    1. NG: REPAIR OR REPLACE AIR INDUCTION SYSTEM 
    2. OK: GO TO NEXT STEP. 
  7. CHECK CONNECTION OF PCV HOSE 

    OK: PCV hose is connected correctly and PCV hose has no damage. 

    1. NG: REPAIR OR REPLACE PCV HOSE 
    2. OK: GO TO NEXT STEP. 
  8. CHECK FUEL PRESSURE (See  ON-VEHICLE INSPECTION  ) 
    1. Check fuel pressure (high or low fuel pressure).

      Standard: 

      FUEL PRESSURE SPECIFICATIONS

      Item Specified Condition
      Fuel pressure 304 to 343 kPa (3.1 to 3.5 kgf/cm2 , 44 to 55 psi)
    1. NG: REPAIR OR REPLACE FUEL SYSTEM 
    2. OK: GO TO NEXT STEP. 
  9. INSPECT FUEL INJECTOR ASSY (See  INSPECTION  ) 
    1. Check injector injection (high or low fuel injection quantity or poor injection pattern).

      Standard: 

      INJECTION VOLUME SPECIFICATIONS

      Injection Volume Difference Between Each Injector
      76 to 91 cm3 (4.6 to 5.5cu in.) /15 seconds 15 cm3 (0.9 cu in.) or less
    1. NG: REPLACE FUEL INJECTOR ASSY (See appropriate  Fuel Systems  article) 
    2. OK: GO TO NEXT STEP. 
  10. REPLACE AIR FUEL RATIO SENSOR 
    1. GO TO NEXT STEP. 
  11. PERFORM CONFIRMATION DRIVING PATTERN (See  DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1)  ) 

    HINT:

    Clear all DTCs prior to performing the confirmation driving pattern (see DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1) ).

    1. GO TO NEXT STEP. 
  12. READ OUTPUT PTC (A/F SENSOR PTC OUTPUT AGAIN) 
    1. Read the DTC using the hand-held tester or the OBD II scan tool.

      Result: 

      DTC OUTPUT RESULT

      Display Proceed to
      DTC P2A00 is not output A
      DTC P2A00 is output B
    1. B: REPLACE ECM (See  REPLACEMENT  ) AND PERFORM CONFIRMATION DRIVING PATTERN (See  DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1)   ) 
    2. A: GO TO NEXT STEP. 
  13. CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST 
    1. NO: CHECK FOR INTERMITTENT PROBLEMS (See  CHECK FOR INTERMITTENT PROBLEMS  ) 
    2. YES: DTC IS CAUSED BY RUNNING OUT OF FUEL 
  14. PERFORM CONFIRMATION DRIVING PATTERN (See  DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1)  ) 

    HINT:

    Clear all DTCs prior to performing the confirmation driving pattern (see DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1) ).

    1. GO TO NEXT STEP. 
  15. READ OUTPUT DTC (A/F SENSOR DTC OUTPUT AGAIN) 
    1. Read the DTC using the hand-held tester or the OBD II scan tool.

      Result: 

      DTC OUTPUT RESULT

      Display Proceed to
      DTC P2A00 is output A
      DTC P2A00 is not output B
    1. B: Go to step   19 . 
    2. A: GO TO NEXT STEP. 
  16. REPLACE AIR FUEL RATIO SENSOR 
    1. GO TO NEXT STEP. 
  17. PERFORM CONFIRMATION DRIVING PATTERN (See  DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1)  ) 

    HINT:

    Clear all DTCs prior to performing the confirmation driving pattern (see DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1) ).

    1. GO TO NEXT STEP. 
  18. READ OUTPUT DTC (A/F SENSOR DTC OUTPUT AGAIN) 
    1. Read the DTC using the hand-held tester or the OBD II scan tool.

      Result: 

      DTC OUTPUT RESULT

      Display Proceed to
      DTC P2A00 is not output A
      DTC P2A00 is output B
    1. B: REPLACE ECM (See  REPLACEMENT  ) AND PERFORM CONFIRMATION DRIVING PATTERN (See  DTC P2195, P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK (BANK 1 SENSOR 1)  ) 
    2. A: GO TO NEXT STEP. 
  19. CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST 

    OK: Vehicle has run out of fuel in past. 

    1. NO: CHECK FOR INTERMITTENT PROBLEMS (See  CHECK FOR INTERMITTENT PROBLEMS  ) 
    2. YES: DTC IS CAUSED BY RUNNING OUT OF FUEL 
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