Inspection Procedure

WARNING: This page is about a different variant/trim than selected.

HINT:

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the 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/Active Test/Control the Injection Volume for A/F Sensor.
Perform the Active Test operation with the engine idling (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 Voltage 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 Voltage B1 S1 (Air fuel ratio)	+25%	Rich	Below 3.1 V
AFS Voltage B1 S1 (Air fuel ratio)	-12.5%	Lean	Higher than 3.4 V
O2S B1 S2 (Heated oxygen)	+25%	Rich	Higher than 0.55 V
O2S B1 S2 (Heated oxygen)	-12.5%	Lean	Below 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.

AIR FUEL RATIO SENSOR REFERENCE

Case	Air Fuel Ratio Sensor (Bank 1 Sensor 1) Output Voltage	Heated Oxygen Sensor (Bank 1 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/Active Test/Control the Injection Volume for A/F Sensor/All Data/AFS Voltage B1 S1 and O2S B1 S2; and 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 help determine if the vehicle was moving or stationary, 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.

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/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

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/Active Test/Control the Injection Volume for A/F Sensor.
Perform the Active Test operation with the engine idling (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 Voltage 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.

Standard

VOLTAGE STATUS CHART

Techstream Display (Sensor)	Injection Volume	Status	Voltage
AFS Voltage B1 S1 (Air fuel ratio)	+25%	Rich	Below 3.1 V
AFS Voltage B1 S1 (Air fuel ratio)	-12.5%	Lean	Higher than 3.4 V
O2S B1 S2 (Heated oxygen)	+25%	Rich	Higher than 0.55 V
O2S B1 S2 (Heated oxygen)	-12.5%	Lean	Below 0.4 V

Result

RESULT CHART

Status AFS Voltage B1 S1	Status O2S B1 S2	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 leak 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 leak from exhaust system	C
Lean/Rich	Rich	Heated oxygen sensor malfunction	-	Heated oxygen sensor Gas leak from exhaust system	C
Lean	Lean	Actual air fuel ratio lean	May occur	Extremely rich or lean actual air fuel ratio Gas leak from exhaust system	D
Rich	Rich	Actual air fuel ratio rich	-	Extremely rich or lean actual air fuel ratio Gas leak from exhaust system	D
Lean: During Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS Voltage B1 S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1 S2) is consistently below 0.4 V. Rich: During Control the Injection Volume for A/F Sensor, the AFS Voltage B1 S1 is consistently below 3.1 V, and the O2S B1 S2 is consistently higher 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 5

D: GO TO NEXT STEP AFTER CHECKING ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (See INSPECTION PROCEDURE )

A: Go to next step

CHECK FOR EXHAUST GAS LEAK
1. Check for exhaust gas leaks.
  OK:
  
  No gas leaks.
  
  NG: REPAIR OR REPLACE EXHAUST GAS LEAK POINT
  
  OK: Go to next step
REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST)
1. Replace the front exhaust pipe assembly (TWC: Front catalyst) (See EXHAUST MANIFOLD ).
  NEXT: REPLACE EXHAUST CENTER PIPE ASSEMBLY (TWC: REAR CATALYST) (See EXHAUST PIPE )
CHECK FOR EXHAUST GAS LEAK
1. Check for exhaust gas leaks.
  OK:
  
  No gas leaks.
  
  NG: REPAIR OR REPLACE EXHAUST GAS LEAK POINT
  
  OK: REPLACE HEATED OXYGEN SENSOR (See REMOVAL )