Replacing my bank 2 catalytic converter - 2000 mercury cougar

code p0420 refers to catalytic converter system bank 1 --efficiency below threshold ===causes -- catalytic converter ---wiring---HO2S 2 sensor
The cheapest part to replace is the HO22S sensor so I would do that first. Bump the cat converter soundly with the heal of your hand and if it rattles it needs replacing as it will be cracked internally. Dismiss any tinny rattle as that will be the heat shield loose
The time taken to replace both in an accredited shop will be less than 1 hour so it may pay to shop around and compare prices on the converter and labour costs.

Bank 2 is at the front of the car.

A direct fit converter for your car is is available from Eastern Catalytic. However a reputable muffler shop should be able to install a threaded port for the 02 sensor if you want to go that route. Call around, get prices, and from that you can make a decision.
Hope this helps.

under $100 on ebay. Why replace, they last a long time.

Oxygen sensors are always numbered like this:
Bank 1 sensor 1
Bank 2 sensor 1
Bank 1 sensor 2
Bank 2 sensor 2

Some manufacturers use a kind of shorthand that reads different, but means the same thing:
Sensor 1/1 or O2s 1/1
Sensor 2/1 or O2s 2/1
Sensor 1/2 or O2s 1/2
Sensor 2/2 or O2s 2/2

Bank 1 is always the side of the engine where cylinder number 1 is located and, of coarse, Bank 2 is the opposite side.
On a 4 cylinder engine, there is only 1 bank and it is always referred to as Bank 1.

Sensor 1 is always the upstream sensor (The one located BEFORE the catalytic converter)
Sensor 2 is always the downstream sensor (the one that is located AFTER the catalytic converter.

Hope helps (remember to rate this).

Yes it can be related. If you bought the car from a car lot you may have a window sticker showing a 30 to 90 day warranty. The Catalytic converter can be expensive although it is similar to installing a muffler or header extensions.

The hesitation can be due to the engine controls trying to adjust for the difference in exhaust readings from one side to the other. Or it has excessive backpressure caused by the plugged catalytic converter.

that sounds very high to me... i put high flow performance cats from magnaflow on my cougar and they were $250 a piece... those are top of the line catalytic converters that are made for race style engines to gain more power but can be put on your car even if its fully stock.... i think your mechanic is a little pricy.. even with installation it shouldnt come even close to that much

Yes the front O2 sensor(the one before the cat) could be lazy and cause this also.

Your Catalytic Converter is Clogged up. This is what is Causing it to not run.

HI
yes there is two catalytic converters ???
one for any exhaust pipe bank (left & right) (bank 1 & bank 2 )
if you change the bank 1 ?? may be you need to change the bank 2 today?????
but not to change the same bank two time ???????

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