Inspection Procedure

WARNING: This page is about a different car, the 2008 Toyota Yaris. However, it is still accessible from the selected car via links, so may be relevant.

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 (A/F) sensor, Heated Oxygen (HO2) 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 a 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 A/F and HO2 sensors (AFS B1 S1 and O2S B1 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.

VOLTAGE SPECIFICATION

Tester Display (Sensor)	Injection Volume	Status	Voltage
AFS B1 S1 (A/F)	+25%	Rich	Less than 3.0 V
AFS B1 S1 (A/F)	-12.5%	Lean	More than 3.35 V
O2S B1 S2 (HO2)	+25%	Rich	More than 0.55 V
O2S B1 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 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 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 A/F and HO2 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 B1 S1 and O2S B1 S2; then press the graph button on the Data List view.

HINT:

DTC P2A00 may be set, when the air-fuel ratio is stuck rich or lean.
A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
Read freeze frame data using the Techstream. Freeze frame data record 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.

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00)

Connect a Techstream to the DLC3.
Turn the ignition switch to ON.
Turn the tester ON.
Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result

RESULT CHART

Display (DTC Output)	Proceed To
P2A00	A
P2A00 and other DTCs	B

If any DTCs relating to the A/F sensor (DTCs for the A/F sensor heater or A/F sensor admittance) are output, troubleshoot those DTCs first.

B: GO TO DTC CHART (See DIAGNOSTIC TROUBLE CODE CHART )

A: Go to Next Step

INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE) (See INSPECTION PROCEDURE )
NG: REPLACE AIR-FUEL RATIO SENSOR (See REMOVAL )

OK: Go to Next Step
CHECK HARNESS AND CONNECTOR (ECM - A/F SENSOR) (See INSPECTION PROCEDURE )
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to Next Step
PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

Connect the Techstream to the DLC3.
Turn the ignition switch to ON.
Turn the tester ON.
Select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending.

Read pending DTCs.

Result

RESULT CHART

Display (DTC Output)	Proceed To
P2A00	A
No output	B

B: CHECK FOR INTERMITTENT PROBLEMS (See CHECK FOR INTERMITTENT PROBLEMS )

A: Go to Next Step

REPLACE AIR-FUEL RATIO SENSOR
1. Replace the A/F sensor (See REMOVAL ).
PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

Connect the Techstream to the DLC3.
Turn the ignition switch to ON.
Turn the tester ON.
Select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending.

Read pending DTCs.

Result

RESULT CHART

Display (DTC Output)	Proceed To
P2A00	A
No output	B

B: REPLACE ECM (See REMOVAL )

A: END