So I was hesitant to ask this as I’ll probably get the same answers I found researching the subject. But here goes anyway. Just changed upstream O2 in my 98. I’ve been running with it unplugged for a bit because it ran so poorly when connected. I wanted to take it for emissions testing on Saturday which will be less than 48 hours from now. I didn’t want to reset the pcm because I’m concerned all of the monitors will not be set in time. So question is whether or not to reset using my code reader. I’ve basically come to the conclusion that it’s not necessary. It seems though that it will take just as long either way for the adaptive memory to adjust to the new sensors readings one way or the other. All of the monitors are currently set aside from the O2 monitors. So would it take just as long for those to be ready as it would for all of them or would they ready quicker if the others are currently ready? If anyone knows for sure please let me know.

Awesome! Thanks guys for instilling more confidence in my choice. I’ve always just reset whenever I made any repairs without a worry but I really need to pass emissions soon. And as far as I can remember in CT all of the monitors need to be ready in order to pass.

The only down side is that it’s exactly 1.3 miles from my driveway to my parking space at work so that’s about 5.2 miles I drive just to work and back and stopping home for lunch. And that’s probably 3 warm up cycles if that even matters as much. I guess I’ll have to do a bit of driving between tomorrow night and Saturday morning.

@ Dave, I know that short trips are less than ideal for condensation burn off and what not that’s why I always let my vehicles get up to temp 99% of the time that I start them. I will usually let them idle until operating temp has been reached if need be. Even though idling too much isn’t necessarily good either but it’s better than condensation build up. I keep up on the oil changes as well. And I just sold my wife’s 01 which had the 4 sensors, never had to replace them though.

@ Jordan, I am familiar as well with drive cycles as well. I actually worked at a dealership for a bit and used to take cars on drive car for runs often. But they were always newer and not Jeeps. I only mentioned warm up cycles because I wasn’t sure if drive cycles alone would be enough.

Thanks for all all the help guys but I have read a few times of vehicles taking 500 miles to turn the CEL off. Also I experienced a little hesitation earlier which I hadn’t whilebthe o2 was unplugged. I think I’m just going to reset and drive it as much as possible and see where I end up. I don't want to wait to find out if the CEL will turn itself off. I’d rather reset and see if the light comes back on. And hopefully it won’t take 500 miles to ready the monitors. If I don’t get it through the testing tomorrow oh well.

So about 10 minutes after my last post I started my jeep to head back to work, drive about a half mile and realized no CEL. I’m home now and I plugged in the reader and it has p0132 as a freeze frame and p0135 pending. Also oxygen sensor, oxygen sensor heater, catalyst and evap monitors are not ready. I just replaced the hose from the tank to the vapor canister so that’s why the evap monitor is not ready. Looks like I might also need a cat or downstream o2 sensor. Just going to have to drive it for a week I guess and see where it goes from there.

Well maybe I was jumping to conclusions. I went for a drive last night, another this morning and then a nice longer drive with some highway this evening. This morning when I checked, the catalyst was ready. Still the evap and o2 not ready. P0132 freeze frame remains but the p0135 no longer pending. Then about 5 minutes ago I checked and it’s only the evap remaining not ready and the freeze frame still stored. Not sure but I may have to test some components of the evap system. I’m pretty sure the shop near me has been able to force an evap monitor test on one of my parents vehicles before after doing some repairs. I may need to have this done myself.

So I inquired with a friend who’s family owns the shop nearby. He said CT will pass if one monitor is not ready. He also said that the evap year doesn’t run as often when temps are below 40ish. Not sure if it’s because there isn’t as much fuel vapor when it’s cooler or what.

I checked last last night and the evap monitor was finally ready. Just went and had it tested and all is good. Made it 48 hours before my free retest period was up. Lol.