The best way to get readings is when the car is warm, which means the O2 sensor is in business.
Pin 3 and 2 are specific to my car, you will have to check your tech manual to identify the Lambda pins. As to the EHA, you simply disconnect its harness, you will connect one connection of the harness to the one of the EHA's two pins then you will connect the other pin to the Ammeter (Multimeter set on Amps, with the leads in the proper socket) lead (red for example) then connect the other lead (black) to the remaining connection on the harness. Set the calibration to read current in the 1 to 10 mA and you're good to go.