O2 sensor disconnected, no CEL?

I'm trying to figure out an emissions problem and thought my O2 sensor might be bad.

Disconnected it two days ago, but no check engine light yet.
Shouldn't it throw a code immediately?

If I disconnect the TPS, I get a code immediately, it resets after reconnecting the TPS, so I think my engine computer is still good.

1991 OBD1, 4.0 automatic.

I could be mistaken here, so don't quote me, but I think you'll only get a CEL if it gets a BAD reading... Not necessarily no reading at all. I know the '90 computers are different, but mine doesn't throw a fit either with the o2 unplugged. What type of emissions problem are you having?

Creeper2012 said:

I could be mistaken here, so don't quote me, but I think you'll only get a CEL if it gets a BAD reading... Not necessarily no reading at all. I know the '90 computers are different, but mine doesn't throw a fit either with the o2 unplugged. What type of emissions problem are you having?

Click to expand...

got high CO.
This is a trail rig, very low miles from last inspection.
I put on a new cat. conv. due to rusted connectors, I think the new one was too small.
I may weld the old one back in and try again.

http://www.smogtips.com/failed-high-carbon-monoxide-CO.cfm

The high CO items.