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.

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 an 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.

HINT:

Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the A/F CONTROL operation using the intelligent tester.

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 outputs of the A/F and HO2 sensors (AFS 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 

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

Case	A/F Sensor (sensor 1) Output Voltage		HO2S Voltage (sensor 2) Output Voltage		Main Suspected Trouble Area
1	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	-
	Output Voltage More than 3.35 V Less than 3.0 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage More than 0.55 V Less than 0.4 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	A/F sensor A/F sensor heater A/F sensor circuit
	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage More than 0.55 V Less than 0.4 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Heated oxygen sensor Heated oxygen sensor heater Heated oxygen sensor circuit
	Output Voltage More than 3.35 V Less than 3.0 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4	Injection volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)
	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

• Following the A/F CONTROL 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: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2, 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 a malfunction is 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) 
   1. Connect the intelligent tester to the DLC3.
   2. Turn the ignition switch ON and turn the tester ON.
   3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT 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 

   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 outputs 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 

   VOLTAGE CHART
   
   

   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 

   RESULT CHART
   
   

   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, AND CHECK AND REPAIR EXHAUST GAS LEAKAGE 

   A : Go to next step 

3. CHECK FOR EXHAUST GAS LEAKAGE 

   OK: 

   No gas leakage. 

   NOTE: Replace both the front and rear catalysts (front exhaust pipe).

   NG : REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK : REPLACE EXHAUST MANIFOLD CONVERTER