Q: jeep it threw a p0420 and a p2096 code

Diagnostic Trouble Code P0420 has many, many potential causes other than faulty oxygen sensors. You can’t use a diagnostic trouble code to determine whether an oxygen sensor is bad. To determine if the sensor is in fact bad, the oxygen sensor output would had to have been measured and evaluated on an automotive scope. If the Mechanic did not evaluate the sensor output on an automotive scope, he or she was just guessing that the sensor needs to be replaced. Inasmuch as the trouble codes promptly returned that means either there was nothing wrong with the sensors or, at best, they are merely "part" of the problem. If no tests were done, it will be impossible to know now. P0420 can be caused by a damaged muffler or leaks in the muffler, damaged exhaust manifold or leaks in the exhaust manifold, damaged exhaust pipe or exhaust pipe leaks, misfiring in the engine, oil contamination in catalytic converter, a faulty catalytic converter, a faulty engine coolant temperature sensor, faulty front oxygen sensor, faulty rear oxygen sensor, damaged oxygen sensor wiring, oxygen sensor wiring that is not properly connected, damaged oxygen sensor connectors, a fuel injector that is leaking, fuel pressure that is high, and other causes. Diagnostic Trouble Code P2096 is generally caused by exhaust leaks, clogged injectors, or an intake vacuum leak. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a check engine light diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.