Inspection Procedure

HINT:

Read freeze frame data using an intelligent tester or OBD II scan tool. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

When using intelligent tester: 

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. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   4. Read DTCs.

      Result 

      DTC RESULT DESCRIPTION
      
      

      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 BY 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 output of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2) displayed on the tester.

      HINT:

      • The A/F CONTROL 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 

        STANDARD VOLTAGE SPECIFICATIONS
        
        

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

        Result 

        DTC RESULT DESCRIPTION
        
        

        Status AFS B1S1	Status O2S B1S2	A/F Condition and A/F and HO2 Sensors Condition	Misfires	Main Suspected Trouble Areas	Proceed to
        Lean/Rich	Lean/Rich	Normal	-	Three-Way Catalytic Converter (TWC) Gas leakage 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	B
        Lean/Rich	Lean	HO2 sensor malfunction	-	HO2 sensor Gas leakage from exhaust system	C
        Lean/Rich	Rich	HO2 sensor malfunction	-	HO2 sensor Gas leakage from exhaust system	C
        Lean	Lean	Actual air-fuel ratio lean	May occur	Extremely rich or lean actual air-fuel ratio Gas leakage from exhaust system	A
        Rich	Rich	Actual air-fuel ratio rich	-	Extremely rich or lean actual air-fuel ratio Gas leakage from exhaust system	A

        Lean: During A/F CONTROL, 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 A/F CONTROL, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.

   B: CHECK AND REPLACE AIR FUEL RATIO SENSOR 

   C: CHECK AND REPLACE HEATED OXYGEN SENSOR 

   A: Go to Next Step 

3. CHECK FOR EXHAUST GAS LEAK 

   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)) 

When Using OBD II Scan Tool: 

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420) 
   1. Connect an OBD II scan tool to the DLC3.
   2. Turn the ignition switch to ON and turn the scan tool ON.
   3. Read DTCs using the scan tool.

      Result 

      DTC RESULT DESCRIPTION
      
      

      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. CHECK FOR EXHAUST GAS LEAK 

   OK: 

   No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK : Go to Next Step 

3. INSPECT AIR FUEL RATIO SENSOR 
   1. Inspect the air-fuel ratio sensor (See AIR FUEL RATIO SENSOR ).

      OK 

      CONFIRMATION DRIVING PATTERN
      
      

      Test Item	Specific Condition
      Confirmation driving pattern	No malfunction Is detected
      A/F control (Inspection procedure)	Standard value

   NG: REPLACE HEATED OXYGEN SENSOR 

   OK : Go to Next Step 

4. INSPECT HEATED OXYGEN SENSOR 
   1. Inspect the heated oxygen sensor (See HEATED OXYGEN SENSOR ).

      OK 

      OS2 TEST RESULT
      
      

      Test Item	Specific Condition
      OS2 test result	Test result is normal
      Confirmation driving pattern	No malfunction is detected
      A/F control (Inspection procedure)	Standard value

   NG: REPLACE HEATED OXYGEN SENSOR 

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