Where is the oxygen sensor bank1 3 on a 1999 chevy s-10?

The location of the oxygen sensor Bank 1, Sensor 3 on a 1999 Chevy S-10 depends on the engine. There's no single answer. Bank 1 refers to the side of the engine where cylinder #1 is located. Sensor 3 is typically a downstream sensor in the catalytic converter.

To find it, you'll need to:

1. Identify your engine: Look for an engine code (like 2.2L, 4.3L) on a sticker under the hood or in the driver's side doorjamb.

2. Consult a repair manual: A repair manual specific to your year and engine will show you a diagram of the exhaust system and pinpoint the location of all the oxygen sensors. Chilton's, Haynes, and online resources like Mitchell 1 are good options.

3. Use a visual inspection (with caution): Once you've determined which side is Bank 1, look for a sensor wired into the exhaust system after the catalytic converter. Be careful, the exhaust system will be hot if the engine has recently run. Wear gloves to protect your hands.

Without knowing the specific engine size, providing a precise location is impossible. Using a repair manual tailored to your vehicle is the most reliable method.