Conditioning For Sensor Testing

HINT: 

Perform the operation with the engine speeds and durations described below prior to checking the waveforms of the air fuel ratio and heated oxygen sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

Fig 1: Engine Speed And Time Graph

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1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up with all the accessories switched off, until the engine coolant temperature stabilizes (Procedure "B").
3. Run the engine at an engine speed of between 2500 RPM and 3000 RPM for at least 3 minutes (Procedure "C").
4. While running the engine at 3000 RPM for 2 seconds and at 2000 RPM for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the tester (Procedure "D").

   HINT: 

   • If either of the voltage outputs of the Control the Injection Volume for A/F 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 using the Techstream.
   • If the three-way catalyst converter has deteriorated, the heated oxygen sensor (located behind the three-way catalyst converter) voltage output fluctuates up and down frequently, even under normal driving conditions (active air fuel ratio control is not performed).

Fig 2: Air Fuel Ratio Sensor Output Voltage Graph

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1. AIR FUEL RATIO CONTROL 

   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.

   1. Connect the Techstream to the DLC3.
   2. Start the engine and turn the tester on.
   3. Warm up the engine at an engine speed of 2500 RPM for approximately 90 seconds.
   4. Select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
   5. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
   6. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) 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.

      Standard voltage

      Tester Display	Injection Volumes	Status	Voltages
      AFS Voltage B1S1 or AFS B2S1 (Air fuel ratio)	+25%	Rich	Less than 3.1 V
      AFS Voltage B1S1 or AFS B2S1 (Air fuel ratio)	-12.5%	Lean	More than 3.4 V
      O2S B1S2 or O2S B2S2 (Heated oxygen)	+25%	Rich	More than 0.55 V
      O2S B1S2 or O2S B2S2 (Heated oxygen)	-12.5%	Lean	Less than 0.4 V

      WARNING:

      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 on the tester: 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.