I made the mistake of deleting the OBD codes after an O2 fail code and check engine light showed up. That mistake wiped out all the monitor profiles. So far, I have 60 miles and associated fuel invested in getting those various engine monitoring systems to reset. How long should this take? I've been constantly repeating the profiles I found here on the forum, which is difficult to accomplish accurately with 70-80 MPH traffic on DFW freeways. Maybe I need to get out there at 2 AM with all the drunks....might be more safe. To date, I've run the complete profile about five times(with the bad O2 sensor). (It runs fine).

This is a totally rust free 40,0000 mile Texas XJR....is this a typical life for O2 sensors? So far, both fuel pumps have failed, all four shock bushing/donuts have been replaced, and now this....GRRRR.

 

O2 sensors usually last considerably longer than 40k. The one that usually
fails first is the drivers side upper. It is not terribly hard to replace but takes
a little bit of time to get things out of the way to get to it.

 

Is it just the O2 monitor which won't set?

 

No, most of the emissions related monitors switched to red "not ready" status. So if my state emissions inspection was due (fortunately, it's still a few months away), it wouldn't pass.

Regarding the O2 sensor (driver side), I'm going to pull the connector and check for corrosion....doubtful that's the problem.

 

If the car threw a code for a failed O2 sensor, why not replace the O2 sensor? Yes, clearing a MIL will reset the monitors and you have to go through the drive cycle to get them to test and hopefully clear, but I can't see why it would go ready if you didn't change the faulty O2 sensor that created the issue in the first place. Just because it seems to be running fine, it doesn't logically follow that all is well and the code was incorrect...sometimes they are, absolutely...but what you're describing sounds like the car knows there's something wrong and all I can say is if I were in your shoes, I'd change the O2 sensor the code flagged before and see what happens.

Checking the connectors is always a good idea, but I can tell you that only one time in over 30 years have I ever had a connector cleaning resolve a MIL. Its virtually always been the sensor that I had to change to correct the problem.

 

When I got my XJR it flagged up a faulty O2 sensor but clearing the code stopped it coming back. Getting the sensor changed still made it run better & use a bit less fuel though. So I'd follow mayhen's advice.

 

I understand why an O2 failure would screw up an O2 related monitor. But it would seem that an item like the CAT or fuel pressure related monitors would still reset....maybe not...or maybe it just takes a long time.

Yes, I'm resigned to replacing the O2 sensor.

 

For an '02 model year, you will need 7 of the 8 I/M to be green for the emissions test to pass in Texas. '01 and older, it's only 6 of the 8 to pass. I just went through this with my LS-swapped '00 XJR (not the same scenario as you, I recognize) when trying to get it to pass its final emissions test for reregistration. It took for-freaking-ever for the GM drive cycle to set enough of them to go through and the CAT was the holdout....

 

A monitor that's unhappy means many codes can't flag and it can also mean that other monitors won't set.

If a faulty O2, fix it urgently as cat damage is likely otherwise (& monitors won't set).