Short and long term are -100 on both?

[Tloftis]

1997 Mazda B4000 4x4 4.0 engine. I have only once code and it is the dtfe. I have already replaced this and the mil light went out and has not been back on. I may be looking at old codes. I am using a Snap on Modis with 9.4 software. and........... I am a rookie diy guy.

Why would the trims be so high on both? 02 sensors are on zero.

THE CATALYTIC CONVERTER HAS BEEN REPLACED WITH A STRAIGHT PIPE AND A BUNG WELDED TO PUT THE 02 SENSOR BACK WHERE IT WAS

[Witsend]

Sounds like engine might not be going in closed loop operation for some reason or other . Engine temp too cold ?, Exhaust may not be getting hot enough for non heated O2 sensors to operate correctly ( if the heat generating cats are now missing)? , Major vacuum leak? , Low fuel pressure. Maybe if O2 sensors were screwed into bungs while the bypass pipes were getting Arc Welded on near them they got arc current damaged? If they are not exhaust manifold mounted , try wrapping the exhaust pipes to the O2 sensors and a little past them with header tape to retain more heat inside. Even if you get the front O2s to work and fuel trims down, the light will likely come back on for the downstream O2s , Cat efficiency, or insufficient EGR flow

[Tloftis]

engine temp is nearly always 171 degrees. That may be too low. The scan tool says that it is in open loop.