H21 - Check Resistance of Heated Element On HO2S

- Key "OFF".

- Disconnect suspect Heated Oxygen Sensor (HO2S) from vehicle harness.

- Inspect both ends of the connector for damaged or pushed out pins, moisture, corrosion, loose wires, etc. Service as necessary.

- Measure resistance between KEY PWR circuit and PWR GND circuit at HO2S connector (refer to schematic). H - Test Schematic

- Hot to warm resistance specification is 5.0 to 30.0 ohms.

- Room temperature resistance specification is 2.0 to 5.0 ohms.

- Is resistance within specification?

Yes -- Go to H22. H22 - Check For Power At HO2S Harness Connector

No -- Replace HO2S. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)