Inspection Procedure

HINT:

Hand-held tester only:

Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL 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 operation using a hand-held tester.

Connect a hand-held tester to the DLC3.
Start the engine and turn the tester ON.
Warm up the engine at an engine speed of 2,500 RPM for approximately 90 seconds.
On the tester, select the following menu items: DIAGNOSIS/ENHANCED OBD II/ACTIVE TEST/A/F CONTROL.
Perform the A/F CONTROL 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 A/F and HO2 sensors (AFS B1S1 and OS2 B1S2) displayed on the tester.

HINT:

The A/F CONTROL 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:

SENSOR VOLTAGE SPECIFICATIONS

Tester Display (Sensor)	Injection Volumes	Status	Voltages
AFS B1S1 (A/F)	+25 %	Rich	Less than 3.0
AFS B1S1 (A/F)	-12.5%	Lean	More than 3.35
O2S B1S2 (HO2)	+25%	Rich	More than 0.55
O2S B1S2 (HO2)	-12.5%	Lean	Less than 0.4

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.

Fig 1: Air-Fuel Ratio Sensor And Heated Oxygen Sensor Output Voltage Delay Graphical Representation

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Following the A/F CONTROL 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 on the tester: DIAGNOSIS/ENHANCED OBD II/ACTIVE TEST/A/F CONTROL/USER DATA/AFS B1S1 and O2S B1S2, and press the YES button and then the ENTER button followed by the F4 button.

HINT:

Read freeze frame data using a hand-held tester or OBD II scan tool. 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.

INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A24 Air-Fuel Ratio (A/F) sensor connector.

Measure the resistance between the terminals of the A/F sensor connector.

Standard:

TESTER CONNECTION AND CONDITION SPECIFICATIONS (1 OF 3)

Tester Connections	Specified Conditions
HT (1)-+B (2)	Between 1.8 Ω and 3.4 Ω at 20°C (68°F)
HT (1)-AF- (4)	10 kΩ or higher

Reconnect the A/F sensor connector.

NG: REPLACE AIR-FUEL RATIO SENSOR

Fig 2: View Of A24 Air-Fuel Ratio Sensor Connector

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

OK: Go to next step.

INSPECT EFI RELAY

Remove the EFI relay from the engine room R/B.

Check the EFI relay resistance.

Standard:

TESTER CONNECTION AND CONDITION SPECIFICATIONS (2 OF 3)

Tester Connections	Specified Conditions
3-5	10 kΩ or higher
3-5	Below 1 Ω (when battery voltage applied to terminals 1 and 2)

Reinstall the EFI relay.

NG: REPLACE EFI RELAY

Fig 3: Measuring EFI Relay Resistance

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

OK: Go to next step.

CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)

Disconnect the A24 A/F sensor connector.
Turn the ignition switch to ON.

Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

Standard:

TESTER CONNECTION AND CONDITION SPECIFICATIONS (3 OF 3)

Tester Connections	Specified Conditions
+B (A24-2) - Body ground	Between 9 V and 14 V

Turn the ignition switch to OFF.
Disconnect the E4 ECM connector.

Check the resistance.

Standard (Check for open):

TESTER CONNECTION AND CONDITION SPECIFICATIONS (FOR OPEN)

Tester Connections	Specified Conditions
HT (A24-1)-HA1A (E4-5)	Below 1Ω
AF+ (A24-3) - A1A+ (E4-23)	Below 1Ω
AF- (A24-4) - A1A- (E4-31)	Below 1Ω

Standard (Check for short):

TESTER CONNECTION AND CONDITION SPECIFICATIONS (FOR SHORT)

Tester Connections	Specified Conditions
HT (A24-1) or HA1A (E4-5) - Body ground	10 kΩ or higher
AF+ (A24-3) or A1A+ (E4-23) - Body ground	10 kΩ or higher
AF- (A24-4) or A1A- (E4-31) - Body ground	10 kΩ or higher

Fig 4: View Of A24 A/F Sensor Connector

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Fig 5: View Of E4 ECM Connector

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Reconnect the ECM connector.
Reconnect the A/F sensor connector.

Fig 6: A/F Sensor 1 System Reference Diagram

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: REPLACE ECM (See ECM (1ZZ-FE/2ZZ-GE) )