OBDII O2 Sensor Not Ready

[oldskewel]

I just went through something similar:

https://xoutpost.com/bmw-sav-forums/...ncomplete.html

Mine was the O2 sensor *heater* readiness monitor being incomplete. Is that what yours is? I believe that is the one that takes the longest to complete under normal driving, even when everything is perfect.

I did replace the rear, original O2 sensors (and had replaced the front ones 30k miles earlier), and then waited about 200 miles of regular driving for the monitor to show as ready. But I am not sure at all that I needed to replace the sensors. I tested resistance of the heater elements in those sensors and they were normal, but I ran out of options and patience and did the replacement.

You should be able to check those readiness monitors on your OBD2 reader, unless it is a really low-end model. So that would at least take any mystery out of the smog check. No need to go there again until your reader is showing no codes and all monitors ready. And once you've got that, you should be sure to pass unless you fail the visual inspection.

[workingonit]

Originally Posted by oldskewel

... and then waited about 200 miles of regular driving for the monitor to show as ready.... I ran out of options and patience and did the replacement.....

Good luck getting your vehicle ready for emissions testing; it may test your patience, as it did for one of my vehicles.

I have always scanned my vehicles for "monitor readiness" (on my old Innova 3100i scan-tool for many years; previously I had done a pre-test scan with a Snap-On scanner at a friend's shop, ever since 1998), prior to going to the inspection station. The Innova tool has three readiness lights: red, yellow, and green. "Green" means OK.

I now have a Foxwell NT 510 Elite, with BMW and GM programming; I haven't tried using it for emissions readiness tests yet, but I hope it'll help pinpoint exact details that may help me for future readiness testing, with no long drive cycle periods necessary.

If the car showed not ready, or had a fault cleared, I'd have to follow a series of General Motors "Drive Cycles"
(all of my vehicles post-OBD2 inception have been GM, until I got the X5 recently), until the monitors all went green. Sometimes, it was a long process.

Most recently, at least in the last five or so years, I had to do drive cycles on three vehicles:

• 1) '98 GMC 1500 after clearing misfire and oxygen sensor faults, because the wife hadn't told me about them until after the inspection was already overdue; after the repairs on day one, I drove the truck about 50 miles before it was ready,
  
  
• 2) '04 Chevy 2500HD after not driving it for two months, and again, at the last minute, replaced another oxygen sensor, cleared the fault, and drove it 30 miles to go "green" on the monitors, and stopped by the inspection station on the way home (not bad!), and
  
  
• 3) '09 HHR Panel, which I had been using as my daily driver on my 120+ mile-per-day commute to work, but parked it a month before retirement because it suddenly needed several repairs (brake pads, wheel sensors, VVT actuator, MAF sensor, Evap system faults) that I had put off while working/commuting 16 hours a day for the previous three months; after I parked it, then retired, I finally needed it again a year later, so I began the repairs.
  I fixed the first four items in a short time, cleared codes, and was driving the cycle before another hard evap code appeared. I replaced the evap canister vent valve, blew out the lines, and cleared the codes again. Since the inspection/registration had expired during the inactive year it sat parked, I got a temporary 10-day permit for driving the test cycle. I'm glad it was a 10-day permit, because I drove 15 cycles, and almost 400 miles, before it finally showed ready for inspection. It's never had another fault in the five years since then; I've no idea why it wouldn't reset.

[littlex5]

Originally Posted by oldskewel

I just went through something similar:

https://xoutpost.com/bmw-sav-forums/...ncomplete.html

Mine was the O2 sensor *heater* readiness monitor being incomplete. Is that what yours is? I believe that is the one that takes the longest to complete under normal driving, even when everything is perfect.

I did replace the rear, original O2 sensors (and had replaced the front ones 30k miles earlier), and then waited about 200 miles of regular driving for the monitor to show as ready. But I am not sure at all that I needed to replace the sensors. I tested resistance of the heater elements in those sensors and they were normal, but I ran out of options and patience and did the replacement.

You should be able to check those readiness monitors on your OBD2 reader, unless it is a really low-end model. So that would at least take any mystery out of the smog check. No need to go there again until your reader is showing no codes and all monitors ready. And once you've got that, you should be sure to pass unless you fail the visual inspection.

@oldskewel, mine is the O2 monitor not ready (the O2 heater is okay). I'm also suspecting marginally bad O2 sensors but want to ask this forum to get a better idea before taking it to the shop and spend hundreds on replacing the sensors that I may not need. Thanks for sending the link to your previous post. I'll read up on them.