DR-6A Fault Code 21 Oxygen Sensor Circuit

1. With diagnostic read-out tool connected to engine test connector, turn ignition switch off, then disconnect oxygen sensor connector.
2. Connect a jumper wire to harness end of oxygen sensor electrical connector.
3. Start engine, then contact other end of jumper wire to battery positive and negative terminals.
4. If display read-out is at 1 when touching positive post and at 0 when touching negative post, replace oxygen sensor.
5. If display readout does not indicate 1 and 0, proceed to Test 6 step B.