Inspection Procedure

HINT:

Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine condition when 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 DTC P0420) 
   1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
   2. Turn the power switch ON (IG).
   3. Turn the hand-held tester or the OBD II scan tool ON.
   4. On the hand-held tester, select the item: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   5. Read DTCs using the hand-held tester or the OBD II scan tool.
      1. Result: 
      DTC output display
      
      

      Display (DTC Output)	Proceed to
      P0420	A
      P0420 and other DTCs	B

   HINT:

   If any other codes besides P0420 are output, perform troubleshooting for those DTCs first.

   B: GO TO RELEVANT DTC CHART (See Hand Held Tester Display Active Test Table. (2 Of 2)  Figure  ) 

   A: GO TO NEXT STEP 

2. CHECK FOR EXHAUST GAS LEAKAGE 

   OK: No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: GO TO NEXT STEP 

3. INSPECT AIR FUEL RATIO SENSOR (BANK 1 SENSOR 1) (See  WIRING DIAGRAM   ) 

   NG: REPLACE AIR FUEL RATIO SENSOR 

   OK: GO TO NEXT STEP 

4. INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 2) (See  INSPECTION PROCEDURE   ) 

   NG: REPLACE HEATED OXYGEN SENSOR 

   OK: GO TO NEXT STEP 

   REPLACE THREE-WAY CATALYTIC CONVERTER (REPLACE FRONT PIPE) 

   HINT:

   Malfunctioning areas can be found by performing 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 area are malfunctioning or not.

   1. Perform the ACTIVE TEST A/F CONTROL operation.

   HINT:

   The A/F CONTROL operation lowers the injection volume 12.5% or increases the injection volume 25%.

   1. Connect the hand-held tester to the DLC3 on the vehicle.
   2. Turn the power switch ON (IG).
   3. Put the engine in inspection mode (see INFORMATION ).
   4. Warm up the engine by running the engine at 2,500 RPM with the accelerator pedal depressed more than 60 % for approximately 90 seconds.
   5. Select the item: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
   6. Perform the A/F CONTROL operation with the engine in an idle condition (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: AF Sensor Output Voltage & Suspect Area Chart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

To display the graph, enter ACTIVE TEST/ A/F CONTROL/USER DATA, select "AFS B1S1 and O2S B1S2" by pressing the "YES" button followed by the "ENTER" button and then the "F4" button.