Sputtering sound in engine bay

[Jmountjoy]

I have a 2003 Camry SE 4Cyl. My check engine light came on and i hooked a tester up to it and it said exhaust gases to high i believe. Anyways as it idles it has this sputtering sound like a diesel idling. It doesn't affect the way the engine runs or drives but the gas mileage did go down by maybe 50 miles a tank. The noise comes from the rear bottom side of the engine.

[somick]

What is the code?

[jermyjerm]

exhaust leak,before the last o2 sensor.

[toyomoho]

What is the trouble code that was read out?

Could be the flex pipe leaking. This is a flexible section of exhaust pipe between the from pipe and rear. It would just under the firewall.

[Jmountjoy]

The code is P0420 Catalyst Efficiency below threshold (bank 1)