The oxygen sensor detects the oxygen content in the exhaust gases and sends signals to the control unit.
Warm up the engine to operating temperature until the cooling fan turns on.
Measure the voltage between 31 (White (+)) and 32 (black (-)) contacts.
If the voltage is greater than 0.6V during wide throttle acceleration, and if the voltage is less than 0.4V during closed throttle braking at 5000rpm, then the oxygen sensor is normal.
Otherwise, disconnect the main wiring harness from the oxygen sensor.
Next, measure the voltage between the connector pin and ground.
If the voltage is greater than 0.6V during wide throttle acceleration, and if the voltage is less than 0.4V during closed throttle braking at 5000rpm, repair an open in the white wire between the oxygen sensor and terminal 31 of the control unit.
Otherwise, the oxygen sensor must be replaced.