DR-5A Fault Code 21 Oxygen Sensor Circuit

1 Connect diagnostic read-out tool to engine test connector, then turn the ignition switch Off.
2. Disconnect oxygen sensor electrical connector.
3. Connect a jumper wire to oxygen sensor electrical connector.
4. Put the system into sensor test mode 02.
5. Contact other end of jumper wire to battery positive and ground terminals and note read-out tool display. Divide diagnostic read-out tool reading by 10.
6. If display on read-out tool indicates 5 volts when jumper wire is connected to battery positive terminal and indicates 0 voltage when jumper wire is connected to battery ground terminal, replace oxygen sensor.
7. If display read-out tool does not indicate 5 volts when jumper wire is connected to battery positive terminal, proceed to step B.