I got replaced new exhaust system with new sensors. Check engine on p0140. Why?

The code means their is no activity on Bank 1 Sensor 2. (the rear-most sensor on the exhaust pipe coming from the side of the engine containing the number one spark plug) Either you have a bad sensor out of the box (it can happen), the sensor isn't plugged in (or isn't plugged in securely) to the electrical connector, or the sensor isn't screwed into the exhaust pipe. It's also possible (not likely) to generate this code if you have a large exhaust leak somewhere between the motor and the sensor. Or if you installed an aftermarket "free flow" exhaust with a long tube (usually aprox 4 inches) that the sensor screws into, exhaust gasses may not be making it to the sensor quickly enough. Also, if the sensor wasn't unplugged prior to dropping the original exhaust, you may have pulled on the wiring harness and damaged the wiring on the vehicle side. Was the code present before the exhaust swap? Are you using a "fancy pants" crazy aftermarket exhaust system? Do you have a digital volt meter? Hope this gets you started :) Good Luck