* Upstream (before the catalytic converter): This sensor is located in the exhaust manifold, relatively close to the engine. It's usually on the passenger side (right side) of the engine, but you should double-check the specific location on your truck.
* Downstream (after the catalytic converter): This sensor is located in the exhaust pipe, after the catalytic converter. Its position will be further down the exhaust system than the upstream sensor. Again, the exact placement can vary but generally on the passenger side.
To be absolutely certain:
1. Consult your vehicle's repair manual: This is the best resource for precise sensor locations and diagrams.
2. Look under the vehicle: Carefully examine the exhaust system for sensors that are threaded into the exhaust pipe. They will typically have a wire harness leading to them.
Remember to be cautious when working under the vehicle and allow the exhaust system to cool completely before attempting any inspection or repair.
