Inspection Procedure

HINT:

Read freeze frame data using a Techstream. 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 a Techstream to the DLC3.
   2. Turn the ignition switch to ON and turn the tester ON.
   3. Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
   4. Read DTCs.

      Result 

      RESULT CHART
      
      

      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 (See  DIAGNOSTIC TROUBLE CODE CHART   ) 

   A: Go to next step 

2. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) 
   1. Connect the Techstream to the DLC3.
   2. Start the engine and warm it up.
   3. Turn the tester ON.
   4. Run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
   5. Select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
   6. Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
   7. Monitor the voltage outputs of the air-fuel ratio sensor and heated oxygen sensor (AFS B1S1 and O2S B1S2) displayed on the tester.

      HINT:

      • The Control the Injection Volume for A/F sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
      • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

      Standard 

      VOLTAGE SPECIFICATION
      
      

      Tester Display (Sensor)	Injection Volume	Status	Voltage
      AFS B1S1 (A/F)	+25%	Rich	Less than 3.0
      	-12.5%	Lean	More than 3.35
      O2S B1S2 (HO2)	+25%	Rich	More than 0.55
      	-12.5%	Lean	Less than 0.4

      Result 

      RESULT CHART
      
      

      Status AFS B1S1	Status O2S B1S2	A/F Condition and A/F and HO2 Sensors Condition	Misfire	Main Suspected Trouble Area	Proceed To
      Lean/Rich	Lean/Rich	Normal	-	Three-Way Catalytic Converter (TWC) Gas leak from exhaust system	A
      Lean	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B
      Rich	Lean/Rich	A/F sensor malfunction	-	A/F sensor
      Lean/Rich	Lean	HO2 sensor malfunction	-	HO2 sensor Gas leak from exhaust system	C
      Lean/Rich	Rich	HO2 sensor malfunction	-	HO2 sensor Gas leak from exhaust system
      Lean	Lean	Actual air-fuel ratio lean	May occur	Extremely rich or lean actual air-fuel ratio Gas leak from exhaust system	D
      Rich	Rich	Actual air-fuel ratio rich	-	Extremely rich or lean actual air-fuel ratio Gas leak from exhaust system
      Lean: During Control the Injection Volume for A/F sensor, the A/F sensor output voltage (AFS) is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V. Rich: During Control the Injection Volume for A/F sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V. Lean/Rich: During Control the Injection Volume for A/F sensor of the Active Test, the output voltage of the HO2 sensor alternates correctly.

   B: REPLACE AIR-FUEL RATIO SENSOR  (See REMOVAL )

   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 LEAK 

   OK: 

   No gas leak. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

   OK: REPLACE FRONT EXHAUST PIPE ASSEMBLY (THREE-WAY CATALYTIC CONVERTER)  (See REMOVAL )

4. CHECK FOR EXHAUST GAS LEAK 

   OK: 

   No gas leak. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

   OK: REPLACE HEATED OXYGEN SENSOR  (See REMOVAL )