On-Vehicle Inspection

INSPECT AIR FUEL RATIO SENSOR

Disconnect the air fuel ratio sensor connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance

AIR FUEL RATIO SENSOR

Tester Connection	Condition	Specified Condition
1 (HT) - 2 (+B)	20°C (68°F)	1.8 to 3.4 Ω

Fig 1: Identifying Air Fuel Ratio Sensor Connector

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

If the result is not as specified, replace the air fuel ratio sensor.

INSPECT AIR-FUEL RATIO COMPENSATION SYSTEM

HINT:

Malfunctioning areas can be identified by performing the A/F CONTROLS (Control the Injection Volume for A/F sensor*2) function provided in the Active Test. The A/F CONTROL (Control the Injection Volume for A/F sensor) 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 (Control the Injection Volume for A/F sensor) operation using the Intelligent tester or Techstream.

*1: Intelligent tester

*2: Techstream

Connect the Intelligent tester or Techstream to the DLC3.
Start the engine and turn the tester ON.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
On the tester, enter the following menus:
1. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
2. Techstream - Select: Powertrain / Engine / 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 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 (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.

AIR-FUEL RATIO COMPENSATION SYSTEM

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

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.

AIR-FUEL RATIO (A/F) SENSOR OUTPUT VOLTAGE CHART

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 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	A/F sensor A/F sensor heater A/F sensor circuit
3	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	HO2 sensor HO2 sensor heater HO2 sensor circuit
4	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely rich or lean)

Following the A/F CONTROL or Control the Injection Volume for A/F sensor procedure enables technicians to check and graph the voltage outputs of both the A/ F and HO2 sensors.
To display the graph, enter the following menus:
1. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / A/F CONTROL SYS / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2; then press the YES button and the ENTER button followed by the F4 button.
2. Techstream - Select: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/ F Control System / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2.