2001 T4R exhaust 2 cats?

[Jaynhunt]

First of all I appreciate the info. Today was the first time I actually looked at the front of the exhaust after all these years. I see there are two cats and looks like two sensors. I know the first sensor before the first cat is the o2 which I need but what about eliminating the second cat? I'm wanting to throw on a Flowmaster Super 44 and don't really see the need for 2 cats. I don't want to destroy the earth but I mean it seems a little much for the 3.4l. Anyways can someone tell me about this rear sensor and what I need to do to eliminate the second cat please.

Thank you

 

[jgue467]

mpgs down the drain

is what you'll get and no power boost to show for it. The front sensor is called the air/fuel sensor (it has a much wider range than a standard o2) while the rear is the 02 sensor you mentioned. The ECM depends on the 2 to compare and run its code that optimizes power and fuel usuage. Without the rear there can be no comparison so ECM goes into limp home mode, you'll waste fuel for no good reason but hey its your gas and who knows what your rig will run like after time. besides why does ur flwmster need to be so forward? :banana:

 

[TheDurk]

is what you'll get and no power boost to show for it. The front sensor is called the air/fuel sensor (it has a much wider range than a standard o2) while the rear is the 02 sensor you mentioned. The ECM depends on the 2 to compare and run its code that optimizes power and fuel usuage. Without the rear there can be no comparison so ECM goes into limp home mode, you'll waste fuel for no good reason but hey its your gas and who knows what your rig will run like after time. besides why does ur flwmster need to be so forward? :banana:

NO. The 4Runner only uses the rear sensor to set the CAT efficiency code (P0420) and the codes related to the sensor itself. Power and MPG depend only on the front sensor, A/F in his case. There is ZERO chance a rear sensor issue puts him in open loop (not really a limp-home mode, but what I assume you meant.)

That said, I'd prefer to keep the sensor and run a simulator to keep my MIL operational. I'd hate to get a code I really needed to know about and not see the light.