* Upstream Sensor (before the catalytic converter): This is usually located in the exhaust manifold or very close to it. It's generally easier to access from underneath the vehicle.
* Downstream Sensor (after the catalytic converter): This sensor is typically located in the exhaust pipe, further downstream from the catalytic converter. Again, access is usually from underneath.
To find them definitively:
1. Consult your vehicle's repair manual: This is the best resource, as it will show exact locations with diagrams. A Haynes or Chilton manual are readily available online or at auto parts stores.
2. Use an online parts diagram: Websites like AutoZone, Advance Auto Parts, or RockAuto allow you to select your specific year, make, model, and engine, and view diagrams showing the sensor locations.
3. Visually inspect: Get under your S10 (safely using jack stands) and look along the exhaust system for the sensors. They are usually threaded into the exhaust pipe and have wiring connected to them. Be cautious of hot exhaust components.
Without knowing your specific engine (a 2.2L, 4.3L, or other), precise location is difficult. Use the resources mentioned above for accurate identification.
