E3: Check For O2 Sensor Failure

Run the engine for a period to warm the sensor & then maintain a steady speed of approximately 2500 rpm
With EM023 disconnected, measure the voltage between EM023/003 & EM023/004.

Is the voltage between 600 mV & 1.0 Volt?

Yes
Go to E4

No
Renew O2 sensor; reconnect plug(s)
Go to E7