6. Check HO2S1 Ground Circuit For Open And Short

1. Turn ignition switch OFF.
2. Disconnect heated oxygen sensor 1 harness connector.
3. Check harness continuity between HO2S1 terminal 4 and ground.

   Refer to Wiring Diagram.

   1. Continuity should exist. 
4. Also check harness for short to power.

OK or NG 

OK: GO TO 7.

NG: Repair open circuit or short to power in harness or connectors.