Check that the circuit between terminals 3 and 4 of the sensor connector (1) is closed (the resistance between the terminals should be 74 Ohm at 20°C)
If the circuit is open, replace the oxygen sensor.
Warm up the engine to operating coolant temperature.
Using wires, connect terminal 3 of the oxygen sensor connector to the "+" terminal of the battery, and terminal 4 to the "-" terminal of the battery.
Connect a digital voltmeter to pins 1 and 2 of the sensor connector.
Measure the oxygen sensor output voltage by pressing the accelerator pedal periodically. When pressing the accelerator pedal, the oxygen sensor output voltage should be 0.6-1.0 V.
Replace the oxygen sensor if necessary.
(Original material on the website: «MitsubishiMan.ru»)