2001 Blazer - engine warning light stays on

You have a problem with the O2 sensor on bank 2, bank 2 is the bank opposite the bank that #1 cylinder is in, but I would recommend that you replace the bank 1 and 2 sensors as a pair, the factory always wanted it done that way, and you know how cheap they are. The O2 or oxygen sensors are located before the catalytic convertors near the exhaust manifold, they will have anywhere from 2 to 4 wires at the connector, you may need a special socket to remove them if access is a issue. When the parts are installed, disconnect the battery for 5 minutes and that will clear the code. Good luck, don't burn yourself!