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 OUTPUT RESULT
      
      

      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. Turn the ignition switch to ON and turn the tester ON.
   3. Start the engine.
   4. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
   5. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
   6. 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).
   7. Monitor the voltage output of the HO2 sensors (O2S B1S1 and OS2 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 

      VOLTAGE OUTPUT OF HO2 SENSORS
      
      

      Tester Display (Sensor)	Injection Volumes	Status	Voltages
      O2S B1S1 (Front HO2 Sensor)	+25 %	Rich	More than 0.5
      O2S B1S1 (Front HO2 Sensor)	-12.5 %	Lean	Less than 0.4
      O2S B1S2 (Rear HO2 Sensor)	+25 %	Rich	More than 0.5
      O2S B1S2 (Rear HO2 Sensor)	-12.5 %	Lean	Less than 0.4

      Result 

      RESULT REFERENCE
      
      

      Status O2S B1S1	Status O2S B1S2	A/F Condition and HO2 Sensors (sensors 1 and 2) Condition	Misfires	Main Suspected Trouble Areas	Proceed to
      Lean / Rich	Lean / Rich	Normal	-	TWC Gas leakage from exhaust system	A
      Lean	Lean / Rich	HO2 sensor (sensor 1) malfunction	-	HO2 sensor (sensor 1)	B
      Rich	Lean / Rich	HO2 sensor (sensor 1) malfunction	-	HO2 sensor (sensor 1)	B
      Lean / Rich	Lean	HO2 sensor (sensor 2) malfunction	-	HO2 sensor (sensor 2) Gas leakage from exhaust system	C
      Lean / Rich	Rich	HO2 sensor (sensor 2) malfunction	-	HO2 sensor (sensor 2) Gas leakage from exhaust system	C
      Lean	Lean	Actual Air-Fuel Ratio (A/F) lean	May occur	Extremely rich or lean actual A/F Gas leakage from exhaust system	A
      Rich	Rich	Actual A/F rich	-	Extremely rich or lean actual A/F Gas leakage from exhaust system	A

      Lean: During A/F CONTROL, the HO2 sensor (sensors 1 and 2) output voltages are consistently less than 0.4 V.

      Rich: During A/F CONTROL, the HO2 sensor (sensors 1 and 2) output voltages are consistently more than 0.5 V.

   B: CHECK AND REPLACE HEATED OXYGEN SENSOR 

   C: CHECK AND REPLACE HEATED OXYGEN SENSOR, AND CHECK AND REPAIR EXHAUST GAS LEAKAGE 

   A: Go to Next Step 

3. CHECK FOR EXHAUST GAS LEAKAGE 
   1. Check for the exhaust gas leakage (See REMOVAL ).

      OK: No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: REPLACE THREE-WAY CATALYTIC CONVERTER (FRONT 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 OUTPUT RESULT
      
      

      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 LEAKAGE 

   OK: No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: GO TO NEXT STEP 

3. INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 1) 
   1. Inspect the heated oxygen sensor (See INSPECTION ).

      OK 

      TEST ITEM AND SPECIFIED CONDITION (1 OF 2)
      
      

      Test Item	Specified Condition
      Confirmation driving pattern	No malfunction is detect
      Inspection procedure	Standard value

   NG: REPLACE HEATED OXYGEN SENSOR (SENSOR 1) 

   OK: GO TO NEXT STEP 

4. INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 2) 
   1. Inspect the heated oxygen sensor (See INSPECTION ).

      OK 

      TEST ITEM AND SPECIFIED CONDITION (2 OF 2)
      
      

      Test Item	Specified Condition
      O2S test result	Test result is normal
      Confirmation driving pattern	No malfunction is detect
      Inspection procedure	Standard value

   NG: REPLACE HEATED OXYGEN SENSOR (SENSOR 2) 

   OK: REPLACE EXHAUST PIPE ASSEMBLY (FRONT PIPE)