P2238 and P0136 codes after exhaust work

Hi all - first time posting here but have been appreciating the help from the forum for some time.

2004 Tacoma 3.4 L V6 automatic 210k miles-

Truck had some exhaust leaks and hole in the muffler for as long as I've had it but recently started showing the P0136 code from the downstream O2 sensor. The sensor seemed fine when I checked it, so I figured the exhaust leaks were triggering the code. I had been meaning to get these fixed anyways.

They cut out 2 flanges and replaced the muffler and the P0136 code went away as I was driving home from the shop.

About a week later (~70 miles driven) the P02238 code and P0136 code appeared when I turned it on first thing in the morning. From what I've seen it looks like I'll probably need to replace A/F upstream sensor and downstream O2 sensor.

Does this have anything to do with the recent exhaust work? Would love to see if anyone has any other ideas or suggestions before I replace both sensors. Thanks!

UPDATE: the codes have been on and off every other day and typically disappear if I leave the truck in the garage overnight. Is this ice build up interfering with the sensors that is occasionally thawing or are the sensors shot?

 

I have same year and engine when I got the P2238 code I replaced bank 1 O2 sensor no more codes. I’m not saying that’s your problem but it’s a good probability. I would think the same for P0136 replace sensor.

If you replace use Denso sensors.