Obviously, you wired it wrong.  Try again.

Using crimp butt connectors down there isn't a good idea. Do a google search for Automotive 4 pin waterproof connector and you'll get search returns which look like this:

Use a pair of those instead of the butt connectors.

The P0138 code is a failed performance test code.

It has nothing to do with your catalytic converter efficiency.

Periodically the computer tests the O2 sensor output voltages. It does the test as you're driving along and you never know it.

In the case of the O2 sensors the computer will force a lean fuel mixture and check the O2 sensors' response voltages.

Then it will force a rich fuel mixture and check the O2 sensors' response voltages.

The computer wants to see those voltages within a specific voltage range. (the same voltage range which your O2 sensor is capable of outputting.)

So about the voltages. (notice these low voltage ranges. That's why you want waterproof wire connections down there)

Your rear O2 sensor operates in a voltage range of 0.1 volts to 0.9 volts.

When the computer forces the lean fuel mixture it doesn't want to see that O2 voltage signal go much below 0.1 volts.

If it does, it throws a code. Something like, O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2).

When the computer forces a rich fuel mixture it doesn't want to see that O2 voltage signal go much above 0.9 volts.

If it does, it throws a code. Something like, O2 Sensor Circuit High Voltage (Bank 1, Sensor 2).

So put all that to that back of your head. You want to figure out what's happening here.

Maybe a good starting place is to see what those HO2S B1S2  (heated oxygen sensor, bank1 sensor2) voltages are when the computer isn't screwing around with the fuel injector pulses while doing its tests.

Grab a cheap scanner. Go to Live Data. Make sure the Accord is warmed up (scanner will say "CL" ((Closed Loop))

1st) Check the Long Term Fuel Trim. You want to see an easily manageable percentage, (either adding or subtracting 10% or less).

2nd)  look at the HO2S B1S2 data in Graph mode. You want to see it hovering around 0.5 volts. It should look something like this:

If you're seeing a similar waveform on your scanner then your wiring is fine and your HO2S B1S2 is functioning.  It's probably that your Honda Accord doesn't like the Bosch O2 sensor and maybe it would be happier with a Denso when it's performing the rich/lean voltage test.

No matter what, get rid of those butt connectors. They're going to cause you grief down the road.

Just 1 more thing. You have to be careful down there. You have 12 volts on one of those wires providing power to that heater in the O2 sensor. If you were to cross that with the O2 sensor output going to your computer, you'd fry your computer.