Test TC-189A - Post-Catalyst O2 Sensor Heater Failure
NOTE:
For connector terminal identification, refer to CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS
article in this section.
CAUTION:
Allow Oxygen Sensor (O2S) to cool to room temperature before checking resistance.
- Disconnect post-catalyst O2S connector. Using an external ohmmeter, check resistance between O2S connector (component side), ASD relay output circuit (White wire) and heater ground circuit (White wire). See Figure. If resistance is not 4-6 ohms, replace post-catalyst O2S and perform TEST VER-2A. If resistance is 4-6 ohms, go to next step.
- Using an external ohmmeter, check resistance between engine ground and O2S connector, heater ground circuit (Black/Light Blue wire). If resistance is 5 ohms or more, repair open heater ground circuit and perform TEST VER-2A . If resistance is less than 5 ohms, go to next step.
- Start engine. Check voltage on O2S connector, ASD relay output circuit (Dark Green/Orange wire). If voltage is less than 12 volts, repair open ASD relay output circuit and perform TEST VER-2A. If voltage is 12 volts or more, go to next step.
- Using an external ohmmeter, check resistance of O2S signal circuit (Orange/Brown wire) between O2S connector and PCM Black connector. If resistance is 5 ohms or more, repair open signal circuit and perform TEST VER-2A. If resistance is less than 5 ohms, go to next step.
- Check resistance of O2S ground circuit (Black/Light Blue wire) between O2S connector and PCM Black connector. If resistance is 5 ohms or more, repair open ground circuit and perform TEST VER-2A . If resistance is less than 5 ohms, replace O2S and perform TEST VER-2A.