Conditioning For Sensor Testing

HINT: 

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

Fig 1: Identifying Conditioning For Sensor Testing

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• (a) Connect the Techstream to the DLC3.
• (b) Start the engine and warm it up with all the accessories switched off until the engine coolant temperature stabilizes.
• (c) Run the engine at an engine speed of between 2500 RPM and 3000 RPM for at least 3 minutes.
• (d) While running the engine at 3000 RPM for 2 seconds, and then 2000 RPM for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the Techstream.

HINT: 

• If the voltage output of either the air fuel ratio or heated oxygen sensor does not fluctuate, or there is noise in the waveform of either sensor, 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 Control the Injection Volume for A/F Sensor Active Test using the Techstream.
• If the Three-way Catalytic Converter (TWC) has deteriorated, the heated oxygen sensor (located behind the Three-way Catalytic Converter (TWC)) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).

Fig 2: Identifying Catalyst Waveforms

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