Inspection Procedure

HINT:

Read freeze frame data using Techstream. Freeze frame data records 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 Techstream to the DLC3.
   2. Turn the ignition switch ON and turn the tester ON.
   3. Select the following menu items: Powertrain / Engine and ECT / Trouble Code.
   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 CHART 

   A: Go to Next Step 

2. PERFORM ACTIVE TEST USING TECHSTREAM 
   1. Connect Techstream 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: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
   5. Perform the Control the Injection Volume for A/F Sensor 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 VOLTAGE SPECIFICATION
      
      

      Case	Air Fuel Ratio Sensor (Sensor 1) Output Voltage	Heated Oxygen Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Areas
      1	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	-
      2	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Air fuel ratio sensor Air fuel ratio sensor heater Air fuel ratio sensor circuit
      3	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Heated oxygen sensor Heated oxygen sensor heater Heated oxygen sensor circuit
      4	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Fuel pressure Gas leakage from exhaust system (Air fuel ratio extremely lean or rich)

      Following the Control the Injection Volume for A/F Sensor 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: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 then press the graph button on the Data List view.

      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  5

   D: CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR-FUEL RATIO, REPLACE FAULTY AREA AND GO TO NEXT STEP 

   A: Go to Next Step 

3. CHECK FOR EXHAUST GAS LEAKAGE 

   OK: 

   No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: Go to Next Step 

4. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY 
   1. Replace exhaust manifold converter sub-assembly (See REMOVAL ).

   NEXT: REPLACE CENTER EXHAUST PIPE ASSEMBLY  (See COMPONENTS )

5. CHECK FOR EXHAUST GAS LEAKAGE 

   OK: 

   No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: REPLACE HEATED OXYGEN SENSOR