My engine light came on with a diagnosis stating 2 possible bank 1 problems. They told me it could be my oxygen sensor or my cat. convertor. I had my emissions test last year with a perfect score, all zero readings basically. My car runs fine with the same fuel economy for the past 5 years. What should I do first? Can I continue to drive the car the way it is or can I do further damage my car?

the cold from hell,,
CAT monitor. know it well, too well.

no its not that.
the code tells that engine has a lazy or dead cat.
no engine stated.
its and XL-7 not and XL7, they are different cars.
3.6L V6
bank one is failing the person who told you bank 2 is full of beans.

"Catalyst Efficiency Below Normal (Bank 1)" SM quote. we change the front B1S1 front sensor first.
then the B1S2, sensor next.
then the CAT if sure no exhaust leaks are on Bank1.
S1 is front
S2 is rear
bank 1, is cylinder 1 side
bank 1 is,, right bank, usa is passenger side

look for leaks first in exhuast
then bad 02s, on right side , damage to wires.
the new sensors.
then new cat, $$$$$$$$$$$$$$$$$$$ last

sensor 2 is the oxygen sensor and is after the cat converter
sensor 1 is a heated oxygen sensor and is in the exhaust manifold or before the cat converter
two completely different sensors

code p 0136 refers to heated oxygen sensor (HO2S) 2 bank 1 ---circuit malfunction===causes ---heating inoperative ---wiring---HO2S--- ECM
also refers to oxygen sensor (O2S0 2 bank 1---circuit malfunction===causes --- wiring---O2S ---ecm
it also refers to heated oxygen sensor (HO2S) 2 bank 1 ---no signal===causes ---wiring --- HO2S---
code p 0137 refers to HO2S 2 bank 1 ---low voltage -===causes --exhaust leak---wiring short to ground ---HO2S--- ECM
it also refers to O2S 2 bank 1---low voltage ===causes exhaust leak---wiring short to ground ---O2S ---ECM
to set you up here-- there are 4 oxygen sensors in the system
2 are heated oxygen sensors (HO2S) on in each exhaust manifold or exhaust pipe before the cat converter and
2 oxygen sensors (O2S) -- one in each exhaust pipe after the cat converters
heated oxygen sensors have 4 wires and O2S sensors normally only 2 wires
it is more that possible that you changed the wrong sensors and in the process damaged the delicate wires with the incorrect spanner being used

On V engines one of the cylinder heads is located further forward than the other. That is the side that has cylinder #1 on it. That is bank 1. The other side is bank 2. There are 2 oxygen sensors-one in front of the cat convertor and one behind it. Sensor 2 is behind the convertor. It looks kind of like a spark plug with wires coming out the top

Oxygen sensors are located in your exhaust usually 2 - 1 upstream (in front of cat.converter) 1 downstream (behind cat.converter) and from under the vehicle.

A v-6 or v-8 engine will have two banks. Bank one is the side of the engine with the number 1 cylinder. Bank 2 is the other side of the engine. In your case Bank 1 is cylinders 1-3-5 on the back side of the engine closest to the firewall. Bank 2 is cylinders 2-4-6 on the other side of the engine.

You have two cats bank 1 and bank 2. There are two oxygen sensors before each cat that help determine fuel trim and are refered to as sensor 1 and two oxygen sensors after the cats that monitor cat efficiency and are referred to as sensor 2. The bank 1 sensor 2 O2 sensor is either providing a higher than expected signal or is switching like the sensor 1 O2's. If either of these has occurred the PCM detects that the cat is no longer working as it should and sets the code/turns on the check engine light.

9 times out of 10 it is a cat that has gone bad.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

bank 1 will be whichever side cylinder 1 of your engine is and bank 2 will be the opposite side. It's named bank 1 and bank 2 so that no matter how the engine is laid out, bank 1 is always on the same side as cylinder 1. I cannot say whether the right hand or the left hand one will be bank 1 as I do not know where your cylinder 1 is. The garage should know

code p 0138 refers to 2 items
1--heated oxygen sensor(HO2S) 2 bank 1--high voltage ==causes --wiring short to positive --HO2S---ECM
2--oxygen sensor (O2S) 2 bank 1--high voltage ===causes wiring short to positive ---ECM
code p 0139 refers to 2 items
1--- heated oxygen sensor (HO2S) 2 bank 1--slow response ===causes --heating inoperative --wiring--ECM
2--oxygen sensor (o2S) 2 bank 1 slow response ===causes --wiring --- O2S

heated oxygen sensors9HO2S) are in the exhaust manifold before the cat converter
Oxygen sensors (O2S) are after the cat converter
it is indicated that the HO2S is faulty-
check the wiring and /or replace both sensors

You have a V6 engine, bank one is the row of cylinders on the passenger (right) side, bank two is the row of cylinders on the drivers side (left). Your codes indicate an inefficiency in the cat on the left side but this could be due to a bad O2 sensor or an engine that is out of tune and overloading the cat. This car seems too new to have a bad cat. I would change the plugs and the O2 sensor after the cat before going any further. The reason I say the O2 after the cat, it's the one that is critical in sensing cat efficiency. What is the mileage?

I think you will find the aftermarket Cat Conv. is the source of your problem, but without hooking up to the factory test equipment at my disposal at my Ford dealer this at best and educated guess based on 20 years of emission related work, I am a Ford certified master electronics technician