H18 - Check HO2S Circuit For Short to Ground

- Key "OFF".

- Breakout box installed, Powertrain Control Module (PCM) disconnected.

- Heated Oxygen Sensor (HO2S) disconnected.

- Measure resistance between the HO2S circuit test pin at the breakout box and test pins 40, 46 or 49 where applicable at the breakout box.

- Is each resistance greater than 10,000 ohms?

Yes -- Go to H19. H19 - Check HO2S For Short to Ground

No -- Service short circuit. Remove breakout box. Reconnect PCM, HO2S, and any other components that are disconnected. Drive vehicle 5 miles/55 mph. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)