Recurrent P0420 code

Hello all- wanted to see if this sounds on the up and up to y’all. I have a 2015 4cyl that keeps throwing a P0420 code, got 136,000 miles currently. Gotta get it fixed because government shippers require no CEL (otherwise I would ignore since Texas got rid of emissions testing) Local shop said they found fuel in the oil and recommended replacing all 4 injectors and seals for around $1800.

Based on everything I’ve read this could cause the code, but the price seems high- is it a doable weekend job to replace them myself?

 

Providing there are no exhaust leaks P0420 is almost always a failed catyletic converter.

While injectors could possibly cause a converter to prematurely fail if they were leaking or overfueling you would have other symptoms like misfires, fuel trim codes, hard starting when hot, black smoke, and/or poor fuel economy.

I would not start by throwing a set of injectors at it, I would start with reading data and verifying it is in proper fuel control.
Once fuel control is verified I'd want to check converter function by looking at upstream and downstream o2 activity, the downstream sensor should stay relatively steady at around 700mv at hot idle and while driving at a steady speed if the converter is functioning properly.