Where on a 1994 Chevy blazer is the oxygen sensor located bank one one?

On a 1994 Chevy Blazer, the Bank 1, Sensor 1 oxygen sensor is located in the exhaust manifold or very close to it, on the passenger side of the engine. Bank 1 always refers to the side of the engine containing cylinder #1. Since the Blazer's engine is likely a V6 or V8, cylinder #1 is generally on the passenger side.

However, the exact location can vary slightly depending on the engine (4.3L V6, 5.7L V8, etc.). You'll need to consult a repair manual specific to your Blazer's engine to get the precise location. A Chilton's or Haynes manual will have diagrams showing the sensor's placement. You can also find diagrams online by searching for "[your Blazer's engine size] oxygen sensor location."

Be aware that the sensor is threaded into the exhaust system and may be difficult to access. You'll likely need a socket and possibly an extension to reach it.