Inspection Procedure

HINT:

Read freeze frame data using an intelligent tester. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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 ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420) 
   1. Connect an intelligent tester to the DLC3.
   2. Turn the ignition switch to ON and turn the tester ON.
   3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   4. Read DTCs.

      Result 

      RESULT REFERENCE
      
      

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

      HINT:

      If any DTCs other than P0420 are output, troubleshoot those DTCs first.

   B: GO TO  DTC TABLE  

   A: GO TO NEXT STEP 

2. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (A/F CONTROL) 
   1. Connect the intelligent tester to the DLC3.
   2. Start the engine and turn the tester ON.
   3. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
   4. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
   5. Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
   6. Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2) displayed on the tester.

      Result: 

      A/F sensor reacts in accordance with increases and decreases in fuel injection volume: 

      +25% = Rich output: 

      Less than 3.0 V 

      -12.5% = Lean output: 

      More than 3.35 V 

      NOTE: The A/F sensor has an output delay of a few seconds and the HO2 sensor has a maximum output delay of approximately 20 seconds.
      A/F SENSOR AND HO2 SENSOR OUTPUT VOLTAGE SPECIFICATION
      
      

      Case	A/F Sensor (Sensor 1) Output Voltage		HO2 Sensor (Sensor 2) Output Voltage		Main Suspected Trouble Areas
      1	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Catalyst Exhaust gas leakage
      	Output Voltage More than 3.35 V Less than 3.0 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage More than 0.5 V Less than 0.4 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	A/F sensor A/F sensor heater A/F sensor circuit
      	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage More than 0.5 V Less than 0.4 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      3	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	HO2 sensor HO2 sensor heater HO2 sensor circuit
      	Output Voltage More than 3.35 V Less than 3.0 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      4	Injection volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Extremely rich or lean actual air-fuel ratio Injector Fuel pressure Gas leakage from exhaust system
      	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Following the A/F CONTROL procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.

      To display the graph, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1 S1 and O2S B1 S2, and press the YES button and then the ENTER button followed by the F4 button.

      Result 

      RESULT REFERENCE
      
      

      Result	Proceed To
      Case 1	A
      Case 2	B
      Case 3	C
      Case 4	D

   B: REPLACE AIR FUEL RATIO SENSOR 

   C: Go to step   4 

   D: CHECK AND REPLACE EXTREMELY RICH OR LEAN ACTUAL AIR-FUEL RATIO, AND GO TO STEP   3 

   A: GO TO NEXT STEP 

3. CHECK FOR EXHAUST GAS LEAKAGE 

   OK: No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: REPLACE THREE-WAY CATALYTIC CONVERTER (BOTH FRONT AND REAR CATALYSTS (FRONT EXHAUST PIPE)) 

4. CHECK FOR EXHAUST GAS LEAKAGE 

   OK: No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: REPLACE HEATED OXYGEN SENSOR