Warm up the engine to operating temperature until the cooling fan comes on.
Measure the voltage between pins 31 (White (+)) and 32 (Black (-)).
If the voltage is greater than 0.6 V during wide-open throttle acceleration, and if the voltage is less than 0.4 V during closed-throttle braking at 5000 rpm, the oxygen sensor is normal.
Otherwise, the main wiring harness from the oxygen sensor must be disconnected.
Next, measure the voltage between the connector contact and ground.
If the voltage is greater than 0.6 V during wide-open throttle acceleration, and if the voltage is less than 0.4 V during closed-throttle braking at 5000 rpm, then the open in the White wire between the oxygen sensor and terminal 31 of the control unit should be repaired.
Otherwise, the oxygen sensor should be replaced.