No convertor? O2 code

[MrRoo]

So I bought a 97 SR5. Come to find out it doesn't have a convertor. Guy put a straight pipe in. I thought it seemed loud. Has new exhaust also. I'm setting #1 upstream O2 codes not downstream. I ordered a new Denso OEM upstream to put in. I would think it would set a convertor efficiency code. But it's not. Any ideas?

 

[fourwd1]

Do you just have the one sensor before the converter/pipe or is there a second after ?

 

[MrRoo]

One upstream and one down stream.