Inspection Procedure

HINT:

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F sensor Active Test. The Control the Injection Volume for A/F sensor function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning. The following instructions describe how to conduct the Control the Injection Volume for A/F sensor operation using the Techstream.

Connect the Techstream to the DLC3.
Start the engine.
Turn the Techstream on.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS B1 S1 and O2S B1 S2) displayed on the Techstream.

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.

VOLTAGE STATUS CHART

Techstream Display (Sensor)	Injection Volume	Status	Voltage
AFS B1 S1 (air fuel ratio)	+25%	Rich	Less than 3.0 V
AFS B1 S1 (air fuel ratio)	-12.5%	Lean	More than 3.35 V
O2S B1 S2 (heated oxygen)	+25%	Rich	More than 0.55 V
O2S B1 S2 (heated oxygen)	-12.5%	Lean	Less than 0.4 V

NOTE: The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.

MAIN SUSPECTED TROUBLE AREA

Case	Air Fuel Ratio Sensor (Sensor 1) Output Voltage	Heated Oxygen Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	-
2	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Air fuel ratio sensor Air fuel ratio sensor heater Air fuel ratio sensor circuit
3	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Heated oxygen sensor Heated oxygen sensor heater Heated oxygen sensor circuit
4	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injector Fuel pressure Gas leak from exhaust system (Air fuel ratio extremely rich or lean)

Following the Control the Injection Volume for A/F sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.
To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / AFS B1 S1 and O2S B1 S2; then press the graph button on the Data List view.

HINT:

Read freeze frame data using the Techstream. 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.

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420)

Connect the Techstream to the DLC3.
Turn the ignition switch to ON.
Turn the Techstream on.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read the DTCs.

Result

RESULT CHART

Result	Proceed to
DTC P0420 is output	A
DTC P0420 and other DTCs are output	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

PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

Connect the Techstream to the DLC3.
Start the engine and warm it up.
Turn the Techstream on.
Run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

Monitor the voltage outputs of the air fuel ratio sensor and heated oxygen sensor (AFS B1S1 and O2S B1S2) displayed on the Techstream.

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 STATUS CHART

Techstream Display (Sensor)	Injection Volume	Status	Voltage
AFS B1S1 (air fuel ratio)	+25%	Rich	Less than 3.0 V
AFS B1S1 (air fuel ratio)	-12.5%	Lean	More than 3.35 V
O2S B1S2 (heated oxygen)	+25%	Rich	More than 0.55 V
O2S B1S2 (heated oxygen)	-12.5%	Lean	Less than 0.4 V

Result

RESULT CHART

Status AFS B1S1	Status O2S B1S2	Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensors Condition	Misfire	Main Suspected Trouble Area	Proceed to
Lean/Rich	Lean/Rich	Normal	-	Three-way catalytic converter Gas leakage from exhaust system	A
Lean	Lean/Rich	Air fuel ratio sensor malfunction	-	Air fuel ratio sensor	B
Rich	Lean/Rich	Air fuel ratio sensor malfunction	-	Air fuel ratio sensor	B
Lean/Rich	Lean	Heated oxygen sensor malfunction	-	Heated oxygen sensor Gas leakage from exhaust system	C
Lean/Rich	Rich	Heated oxygen sensor malfunction	-	Heated oxygen 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	D
Rich	Rich	Actual air fuel ratio rich	-	Extremely rich or lean actual air fuel ratio Gas leakage from exhaust system	D

Lean: During Control the Injection Volume for A/F sensor, the air fuel ratio sensor output voltage (AFS) is consistently more than 3.35 V, and the heated oxygen sensor output voltage (O2S) is consistently less than 0.4 V.

Rich: During 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 heated oxygen sensor alternates correctly.

B: REPLACE AIR FUEL RATIO SENSOR (SENSOR 1) (See REMOVAL )

C: Go to step 4

D: CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO, AND GO TO STEP 3 (See TYPICAL ENABLING CONDITIONS )

A: Go to Next Step

INSPECT FOR EXHAUST GAS LEAK
1. Check for exhaust gas leakage.
  OK: No gas leaks .
  
  NG: REPAIR OR REPLACE EXHAUST GAS LEAK POINT
  
  OK: REPLACE FRONT EXHAUST PIPE ASSEMBLY (THREE-WAY CATALYTIC CONVERTER) (See EXHAUST PIPE )
INSPECT FOR EXHAUST GAS LEAK
1. Check for exhaust gas leakage.
  OK: No gas leaks .
  
  NG: REPAIR OR REPLACE EXHAUST GAS LEAK POINT
  
  OK: REPLACE HEATED OXYGEN SENSOR (SENSOR 2) (See HEATED OXYGEN SENSOR )