Evap, both 02 monitors will not ready
I currently have above vehicle in shop because evap and both 02's monitor are not ready. Another shop replaced all 02 sensors and between owner and shop, they put about 300 miles on car. The other shops notes didn't mention anything about resetting 02 heaters. when I first received vehicle i found no current or pending dtc's. I started buy erasing dtc's and then preforming a 02 heater reset and test drove. Cat and egr pass on my initial test drive. I allowed vehicle to sit for several hours. I then read enabling criteria and made my best attempt to following to do to the “T” but not prefect. I used Verus scanner and retrieved “not run or failed since code cleared" and found several 02 heater and response dtc's. I took the time to read code criteria for heaters and response time. I also made sure pcm was updated with latest software and it is.
I allowed to soak for more than 8 hours and today I found iat and ect neat 3 degrees from each other and battery volts never fell below 10.5 on startup and charging immediately jumped above 14 volts. I have tried evap bay test but will not allow me. It will take me to main test page but scanner reads enabling criteria has failed. I'm at a lost here and would appreciate any help and thank you
This is my first post here and am still familiarizing myself with controls and features. Your patience will be needed
diag.net/msg/m3pypc3oei… If you search O2 and evap you will see several posts. Some type 02 like you did so use that as well but Bob's thread above is most relevant. There are a lot of tips for you on this one. If you need more help, post some data. Which DTCs have not run? Post all the generic data as well.
Hi Adrian, Study the Evap system and resolve issues there first. I think the Evap has to run its self test before the O2 monitors will. A bad tank vent valve or a saturated charcoal canister can be a factor
Clear codes even if there aren't any and start from scratch. Search service info and look at the drive cycle needed to set monitors and perform the drive cycle, Check all temp sensors before starting engine. see if anything is out of line. the intake and coolant temp should be very close after soaking overnight at startup and if they are even just a few degrees off this will cause the monitors…
I agree with Glenn on his comment about looking at the evap system closely. I would also recommend checking the replacement O2s are the correct ones for the vehicle. Especially since you said there were other O2 codes in the not run/failed section. I have experienced more “bad out the box” OE parts the past 4-5 months than I have in my whole career.
Hi William, I have had the same issue with bad out of the box lately. I have caught independents chain stores putting bad sensors back on the shelf a couple of times. I have resorted to paint marking the bad parts now. They hate that. Luckily, dealer parts are still holding on to be reliable, but they are suffering a lot of shipping delays. With Covid lurking around some people just want to…
Check the ftp sensor make sure it’s not at a fixed value that has failed in range happens all too often and will hang up o2 monitors
Also wanted to add if catalyst monitor set oxygen sensors should follow with more time given it cannot set the catalyst without working O2 sensors, the conditions to set O2 have not yet been met but can use its data to set the catalyst
Agreed. Ford has been setting catalyst monitors for years without O2s being ‘ready’.
Hi Timothy, Ford and GM have vastly different strategies from what I have experienced.
That may be true, as there's no way to know what the engineers have in mind when they design monitor runs, but they all have to fall somewhere in the OBD2 guidelines. But, in the last ten years or so, the O2 monitors on GM vehicles are the last thing to run. Ford used that strategy going way back. In old days, you could enable the O2s on Fords by a simple code clear and then starting the…
O2 monitors on later model GMs are the last monitor to clear in almost every case since about 2009 or so, especially on the trucks. They can take a lot of driving to clear. And, as a couple others have pointed out, make sure the Evap will run, so go over that system carefully. Forget the Service Bay test, and concentrate on the Evap system codes that have not cleared as of yet, so you've got a…
If it doesn't set any codes, or have any drivability issues, then I would stop doing any code clears because you are erasing test data and making the system start over again. If it's not coding give it more time and make sure it gets run through a variety of operating conditions. In the link Randy provided you will see that the solution for mine, after fixing a couple base problems, was to…
I agree that the evap monitors have to run and pass before the O2 monitors will run, but you said that there were some O2 heater and response DTC's that have failed since code clear (after the last cold start). You have to correct the set or pending DTC's before O2 monitors will run, so the evap monitor doesn't really matter at this point. What DTC's were showing as failed since code cleared…
The codes may not have failed, but simply not have run. Some scanners will not differentiate between them. You can run yourself down quite a rabbit-hole with that…ask me how I know! LOL!
Thank you for your help. I shall keep you updated this week. You have given a lotta good advice
Monitors have not since after driven for more than 80 miles. Mode 9 does show many attempts have been made to set evap and 02. What i did find is ftp sensor reading at idle in bay at 1.76 volts. when i drove vehicle from one bay to another, ftp was reading 1.45 volts. from my experience, that is a huge fluctuation. I replaced ftp and after 80 miles still no go. At this time customer will take…