Heated Oxygen Sensor (HO2S 2)

Wiring Diagram:

DESCRIPTION
To control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a warm-up three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen.

OPERATION
The ECM/PCM uses the HO2S 2 to monitor the oxygen storage capability of the catalytic converter. Similar to the O2S 1, the HO2S 2 reacts with the oxygen content in the exhaust stream to produce a voltage signal only after the catalytic converter. This voltage ranges from approximately 0.1 volt (high oxygen - lean mixture) to 0.9 volt (low oxygen - rich mixture). Unlike the O2S 1, the HO2S 2 is normal when it's activity appears lazy or inactive. The ECM/PCM compares readings from both the front O2S 1 and the HO2S 2 to determine the catalyst efficiency.

Legend

1. Crankshaft Position Sensor
2. Engine Coolant Temperature (ECT) Sensor
3. Intake Air Temperature (IAT) Sensor
4. Manifold Absolute Pressure (MAP) Sensor
5. Engine Control Module (ECM) / Powertrain Control Module (PCM)
6. Circuit Opening Relay
7. EFI-HTR Relay
8. Heated Oxygen Sensor 2(HO2S 2)
9. Oxygen Sensor (O2S)