Conditioning For Sensor Testing

HINT:

Perform the operation with the engine speeds and durations described below prior to checking the waveforms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

Fig 1: A/F And HO2 Sensors Waveform Graph

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

Connect the intelligent tester to the DLC3 (Procedure "A").
Start the engine and warm it up with all the accessories switched off, until the engine coolant temperature stabilizes (Procedure "B").
Run the engine at an engine speed of between 2,500 rpm and 3,000 rpm for at least 3 minutes (Procedure "C").
While running the engine at 3,000 rpm for 2 seconds and at 2,000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the tester (Procedure "D").
HINT:
- If either of the voltage outputs of the Air-Fuel Ratio (A/F) or Heated Oxygen (HO2) sensor does not fluctuate, or either of the sensors makes a noise, the sensor may be malfunctioning.
- If the voltage outputs of both the sensors remain lean or rich, the air-fuel ratio may be extremely lean or rich. In such cases, perform the following A/F CONTROL using the intelligent tester.
- If the Three-Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).
Fig 2: HO2 Sensors Waveform Graph Behind TWC
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

A/F CONTROL

HINT:

Intelligent 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 an intelligent tester.

Connect the intelligent 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 O2S B1S2orAFS B2S1 and O2S B2S2) 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 voltage

FUEL INJECTION VOLUME CHART

Tester Display (Sensor)	Injection Volumes	Status	Voltages
AFSB1S1orAFSB2S1 (A/F)	+25%	Rich	Less than 3.0
AFS B1S1 or AFS B2S1 (A/F)	-12.5%	Lean	More than 3.35
O2S B1S2 or O2S B2S2 (HO2)	+25%	Rich	More than 0.55
O2S B1S2 or O2S B2S2 (HO2)	-12.5%	Lean	Less than 0.4

CAUTION: 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.

SENSOR OUTPUT VOLTAGE SPECIFICATION

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	-
2	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	A/F sensor A/F sensor heater A/F sensor circuit
3	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	HO2 sensor HO2 sensor heater HO2 sensor circuit
4	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Fuel pressure Gas leakage from exhaust system (Air Fuel ratio extremely lean or rich)

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 or AFS B2S1 and O2S B2S2. Press the YES button and then the ENTER button. Then press the F4 button.