Heated Oxygen Sensor: Rio
- Disconnect front or rear HO2S 4-pin connector. Measure resistance between front HO2S connector terminals No. 2 and 4 (Green wire and Red/Black wire - component side) or rear HO2S connector terminals No. 2 and 4 (Green/Red wire and Red/Black wire - component side). See Figure. HO2S heater resistance should be between 3-6 ohms at 68°F (20°C).
- Connect HO2S connector. Start and run engine at normal operating temperature for at least 10 minutes. Using scan tool, lab scope or voltmeter, monitor appropriate HO2S signal. If using voltmeter or lab scope, connect positive lead to front HO2S connector terminal No. 1 (Yellow/Green wire) or to rear HO2S connector terminal No. 1 (Lightgreen/Red wire). Connect negative lead to ground. HO2S signal should switch from lean to rich, or rich to lean, at least 3 times every 10 seconds. Front HO2S signal should switch between 0-1 volt. Rear HO2S signal should switch between .6-.9 volt. If HO2S is not as specified, replace HO2S.