Replacing o2 sensor heater bank2 sensor 1, do you need to crawl under truck to find and replace? I know its near or on catalytic converter but when I popped the hood it was so crowded I didn't spot exhaust manafold or catalytic converter

There are 4 O2 Sensors on the 1997 GMC Jimmy V6 4.3L. All sensors are accessed from bottom. All sensors are mounted on the exhaust. Three of the sensors are on the Bank 1 side of the engine (Passenger side). Sensor 1 Bank 1 is upstream of Y joint on Passenger Side, Sensor 1 Bank 2 is upstream of Y joint on drivers side. Sensor 2 Bank 1 is mounted down stream of Y before Cat Converter on Passenger side. Sensor 3 Bank 1 is downstream of Cat Converter on passenger side.Good luck and keep me posted

Everything is located underneath the vehicle on exhaust itself... there should be two sensors as well as the catalytic converter that reside underneath on the exhaust.

It's easiest to find them from under the truck. There are 4 total, 2 on each side of the catalytic converter. The ones that make the difference is your truck running are the ones upstream, before the cat, but after the manifold. They're usually fairly easy to spot when you're under them.

Its under the truck.