However, it's almost certainly on one of the exhaust pipes exiting the engine's exhaust manifold. To find it, you'll need to look underneath the car. The sensor is usually a threaded device, often with a single wire cable leading to it. It will likely be near the engine, fairly close to where the exhaust manifolds connect to the rest of the exhaust system.
To locate it definitively:
1. Consult a repair manual: A Chilton's or Haynes repair manual specific to your 1986 Cadillac Fleetwood FWD is invaluable. It will have diagrams showing the exact location of the oxygen sensor(s).
2. Use a wiring diagram: A wiring diagram for your car's year and model will show you where the O2 sensor wire runs from the engine's computer to its location in the exhaust system. Tracing this wire will lead you directly to the sensor.
Remember to be cautious when working under the car. Use jack stands securely and never rely solely on a jack. The exhaust system will be hot after the engine has run, so allow it to cool completely before working near it.
