The test came back PO135 02 heater circuit bank 1 sensor 1. My question is if I buy this and install can it still be other problems? Car has 250,000 miles and I hear a small exhust noise like maybe a gasket? Thanks!

 

Yes, it can be other components that cause your P0135 as that circuit goes through the throttle position sensor, relays, fuse, etc. Bank 1 sensor 1 is the O2 sensor between the engine and firewall. The sensor is not reaching temperature as quickly as it should.