Conditioning For Sensor Testing

HINT:

Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

Fig 1: Engine Speed Graph

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Connect the intelligent tester to the DLC3.
2. Start the engine and warm it up with all the accessories switched OFF, until the engine coolant temperature stabilizes.
3. Run the engine at engine speed of between 2,500 RPM and 3,000 RPM for at least 3 minutes.
4. While running the engine at 3,000 RPM for 2 seconds and 2,000 RPM for 2 seconds, check the waveforms of the A/F and HO2 sensors using the tester or scan tool.
   NOTE: The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.
   Fig 2: Air-Fuel Ratio Sensor And Heated Oxygen Sensor Output Voltage Graph

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

• Following the A/F CONTROL procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors.
• To display the graph, enter the following menus on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2, and press the YES button and then the ENTER button followed by the F4 button.

HINT:

Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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 AND/OR P0430) 
   1. Connect the intelligent tester to the DLC3.
   2. Turn the engine switch on (IG) and turn the tester ON.
   3. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   4. Read DTCs.

      Result 

      DTC OUTPUT
      
      

      Display (DTC output)	Proceed to
      P0420 and/or P0430	A
      P0420 and/or P0430 and other DTCs	B

      HINT:

      If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.

   B : GO TO  DTC CHART 

   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 engine speed of 2,500 RPM for approximately 90 seconds.
   4. On the tester, enter the following menus: 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 output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) 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: 

   A/F SENSOR AND HO2 SENSOR OUTPUT VOLTAGE SPECIFICATIONS
   
   

   Tester Display (Sensor)	Injection Volume	Status	Voltage
   AFS B1 S1 or AFS B2 S1 (A/F)	+25 %	Rich	Less than 3.0
   AFS B1 S1 or AFS B2 S1 (A/F)	-12.5 %	Lean	More than 3.35
   O2S B1 S2 or O2S B2 S2 (HO2)	+25 %	Rich	More than 0.55
   O2S B1 S2 or O2S B2 S2 (HO2)	-12.5 %	Lean	Less than 0.4

   Result: 

   ACTIVE TEST RESULT DETAIL
   
   

   Status AFS B1 S1 or AFS B2 S1	Status O2S B1 S2 or O2S B2 S2	A/F Condition and A/F and HO2 Sensor Conditions	Misfire	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	May occur	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 lean	-	Extremely rich or lean actual air fuel ratio Gas leakage from exhaust system	A

   Lean: During A/F CONTROL, the A/F sensor (AFS) output voltage 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.

   Lean/Rich: During A/F CONTROL of the ACTIVE TEST, the output voltage of the HO2 sensor alternates correctly.

   B : CHECK AND REPLACE AIR FUEL RATIO 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 

   OK: 

   No gas leakage. 

   NG : REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK : REPLACE THREE-WAY CATALYTIC CONVERTER