Most likely locations:
* Before the catalytic converter(s): This is the most common location for the upstream oxygen sensor(s). You'll likely find one or two sensors here, depending on whether your truck has a single or dual exhaust system. Look for a threaded sensor screwed into the exhaust manifold or pipe, near the engine.
* After the catalytic converter(s): This is the typical location for the downstream oxygen sensor(s). These are used to monitor the catalytic converter's efficiency. Again, the number depends on whether you have a single or dual exhaust setup.
To find them:
1. Consult your owner's manual: This is the best place to start. The manual might have a diagram showing the location of the oxygen sensor(s).
2. Use a repair manual: A Haynes or Chilton repair manual for your specific year and model will have diagrams and detailed instructions.
3. Online resources: Search online for "1997 GMC 3500 454 oxygen sensor location" along with any additional information you have (e.g., specific trim level). You might find images or forum posts from others who have worked on the same truck.
4. Visual inspection: With the engine cool, carefully examine the exhaust manifolds and the exhaust pipes close to the engine. Oxygen sensors are typically threaded and have a single wire or wiring harness connected to them. Be cautious, exhaust components can be extremely hot even after the engine has cooled for some time.
Important Safety Note: The exhaust system gets extremely hot. Allow the engine to cool completely before attempting any work near the exhaust. Wear appropriate safety gear, including gloves and eye protection.
