macgyver

So went to get the Jeep inspected yesterday and it failed due to 3 (Catalyst, O2 Sensor, and O2 Sensor Heater) readiness monitors not being ready. This is a first for me, so naturally I looked into it. I've read several articles on this, reading anything from, drive 40-100 miles and try again, to follow these specific guidelines on certain speeds for certain times, etc etc. I've tried it all. I even took a look at the O2 sensors and wiring which seem fine. The downpipes one is just over a year old from when I replaced the entire exhaust (less the header).

I did manage this morning to clear 2 of the monitors following a near 50 mile drive of mostly highway driving. I did roughly 40 miles of 55-65 mph, and the rest was mixed 35-55 mph. When I returned home and connected my OBD 2 reader again, all that was left was the Catalyst monitor. I proceeded to do another few miles of nearly just 35 mph driving and voila it was all good! Then I had the brilliant idea of turning the vehicle off... When I restarted it to head back out, all 3 monitors were back. I reluctantly went back out and did some highway driving, city driving, etc trying to fix it again, and when I returned I was left with a 02 Sensor Heater monitor not ready. I'm starting to get very frustrated with this ( :brick wall: ), and none of the information I've read online seems consistent. Anyone had any actual experience with this, or have any advice? I need this one inspected by Monday and was shooting for today if possible. Appreciate any advice in advance!

As a note, I disconnected my battery to convert the headlights to H4s a few months ago (2-4?) which I'm thinking reset everything in the first place. It's not my typical daily driver which is why it may still be doing this....?

autosurgeon

http://www.obdautodoctor.com/scantoo...ors-explained/

This might help

macgyver

That article goes alittle more indepth than some of the others I have read, but the end result (following the driving directions) has been the same. I have completed nearly every bit of it, with the obvious exception of not going completely in order as I had to drive a bit to get to said highway to actually go that fast that long. But I have completed all of that and then some with all the miles driven. Perhaps there is something wrong with the vehicle that is causing all 3 monitors to be intermittently ready? In the meantime, its cooling off again so that I might try again later...hopefully before the shop closes. Given I get it working again I'll have to tell them not to turn the vehicle off or it will reset them again.

macgyver

So rather sure the vehicle cooled off enough (it's been a few hours since I had it out) and tried again, following the previous comments website directions to a "T" (can't believe how long it takes to coast from 15 to 0!!). Still sitting on a O2 Heater. Suggestions?

SteveMongr

This is all new to me. I am in eastern NC with a 96 XJ and they do not check for codes. Maybe try a different shop?

FYI, there is a recall for 1996 XJ for catalytic converter replacement. The dealer can look up your VIN to see if the free replacement has been already done.

Bustedback

Replace the O2 sensor that is throwing the incomplete heater monitor. I did that song and dance with my step son's Dakota. It wouldn't set an actual code, but the monitor would never reset too. Replaced the O2 and the monitor reset in twenty miles.

autosurgeon

Sluggish heater plate in the o2 most likely..

Metmknice

Almost sounds like the ECU is partially at fault. As, once the monitors are complete and run. Unless, codes are erased or ECU loses power completely they should be complete regardless of shutting off the vehicle.
If you can get it going again, best thing to do is run it around until monitors are complete and take it to your emissions test station and leave it running.

macgyver

Sorry for the delay... Hate leaving a dead, unsolved thread. Tough to say what my fix was, however I attempted to take off the front O2 sensor as I was rather sure my aft one was too new for problems. I couldn't get it off, even after rounding out two of the sides, surprisingly with vice grips! But that's another project. I called it quits after that, cleaned the throttle body which needed doing anyway while I was dirty and started it up. O2 heater went away and everything was good to go! Hard to say if it was just luck, a cold start that "completed" the cycle, or maybe my banging on the sensor that maybe knocked off some dirt. But regardless, it's working now and passed the inspection I needed it to. I'll keep an eye on it in the meantime and report if anything changes! Appreciate the help again.