Heated Oxygen Sensor (Ho2S): Inspection

• Before checking, warm up the engine until the engine coolant temperature reaches 80 to 95°C (176 to 205°F).
• Use an accurate digital voltmeter.

1. Disconnect the oxygen sensor connector, and measure the resistance between terminal 3 and terminal 4.
   Fig 1: Identifying HO2S Temperature/Resistance Reference Table

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2. Replace the oxygen sensor if there is a malfunction.
3. Apply battery voltage directly between terminal 3 and terminal 4.
   NOTE: Be careful when applying the voltage. Damage will result if terminals 1 and 2 are connected to any voltage.
4. Connect a high-impedance digital-type voltmeter between terminal 1 and terminal 2.
   Fig 2: Identifying HO2S Harness Side Connector End View

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5. While repeatedly racing the engine, measure the oxygen sensor output voltage.
   Fig 3: Identifying HO2S Output Voltage Test Specification (Racing Engine)

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   Fig 4: Identifying HO2S Wave Length Graph

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6. If there is a problem, there may be an oxygen sensor malfunction.

Heated oxygen sensor tightening torque: 40-50 Nm (400-500 kg. cm, 29-36 lb. ft)

Fig 5: Identifying HO2S Connector End View

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