Inspection Procedure

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

NOTE:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

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 tester on.
Warm up the engine at an engine speed of 2500 RPM for approximately 90 seconds.
Select the following menu items: 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 Voltage B1 S1 or AFS Voltage B2 S1 and O2S B1 S2 or O2S B2 S2) displayed on the tester.

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.

Tester Display	Injection Volume	Status	Voltage
AFS Voltage B1 S1 AFS Voltage B2 S1 (Air fuel ratio sensor)	+25%	Rich	Less than 3.1 V
AFS Voltage B1 S1 AFS Voltage B2 S1 (Air fuel ratio sensor)	-12.5%	Lean	More than 3.4 V
O2S B1 S2 O2S B2 S2 (Heated oxygen)	+25%	Rich	More than 0.55 V
O2S B1 S2 O2S B2 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.

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	Fuel pressure Gas leakage from exhaust system (Air fuel ratio extremely lean or rich)

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, select the following menu items:
Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1 S1 or AFS Voltage B2 S1 and O2S B1 S2 or O2S B2 S2; then press the graph button on the Data List view.

HINT:

Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. 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.
Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from the transmission.
Bank 2 refers to the bank that does not include the No. 1 cylinder.
A low air fuel ratio sensor voltage could be caused by a rich air fuel mixture. Check for conditions that would cause the engine to run rich.
A high air fuel ratio sensor voltage could be caused by a lean air fuel mixture. Check for conditions that would cause the engine to run lean.