O2 and EVAP monitors never run

Bob Owner/Technician Massachusetts Posted   Latest   Edited  
Resolved
Driveability
Emissions
2013 Buick LaCrosse 3.6L (3 LFX) 6-spd (6T70) — 1G4GC5E37DF174314
P0442 — EVAP System Leak Detected (small leak),
Monitors Incomplete

I hesitated to post this because I may not get a resolution to it, but I think it's worth some discussion anyway for the future. This car is from the auction and has a salvage title. There's 2 strikes right there. The problem is they can't get it through CT emissions because of incomplete readiness.

The O2 monitor and EVAP never run. We replaced the thermostat and MAF sensor to address engine temp and fuel trim issues. I have run the car through several drive cycles from overnight cold soak and we're still stuck at no O2 or EVAP. I can clear codes and all the other monitors will complete and pass. Done it several times. The only code in the system is a PERMANET EVAP small leak code P0442.

I have run evap purge and seal test and it holds vacuum. I don't think a Permanent code should block the monitor from running.

I have watched the enable criteria on the scanner and even when all criteria is met and the O2 monitor is Enabled, it still won't run. I have tried disconnecting the battery and shorting the cables together. I attempted to reflash the PCM but there are no newer calibrations and TIS won't allow me to overwrite with the same calibration.

I even watched the PCM run the engine off natural vacuum evap test but when I look in mode 6 there is no test data stored for any evap test, except purge. It appeared to pass that test as I watched tank pressure climb as the vent was closed with the engine and key off. I couldn't save that data because when the test finished, the pcm shut down and I lost communication.

I'll post some snapshots of the O2 sensors from a cold start and the pids files. The only thing I see at the moment is that the air filter box top and bottom don't match. The screws in the top cover don't align with most of the holes on the bottom piece. We are going to try and locate a new matching intake box. I don't know if there could be some kind of airflow disturbance that the PCM doesn't like. Other than that I would love to here some ideas on what else could be blocking these monitors from running.

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Craig Technical Support Specialist
Illinois
Craig
 

Robert, by any chance is this vehicle E85 compatible? Because I have seen skewed alcohol content calculations effect fuel trims and screw with the evap system. If it's not E85 compatible perhaps a fuel alcohol content test can be performed maybe we have high alcohol content in the fuel, I know it can cause some strange issues. One other though is regarding the vehicles barometer calculations…

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Bob Owner/Technician
Massachusetts
Bob
 

It is E85 but the alcohol content reads about 10% which is normal around here. I have gassed the car up a couple times during my testing so I'm pretty sure it's not a fuel issue. Also the baro is accurate for my location (sea level) 100 kpa

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Craig Technical Support Specialist
Illinois
Craig
 

Ok, we can scratch that off the list. On a cold soak do all of the vehicles temperature sensors agree?

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Craig Technical Support Specialist
Illinois
Craig
 

Robert, rereading the post I see you saw the evap system run up pressure and stop the test, I believe that what was seen was the fuel volatility portion of the monitor running, and the vehicle will not complete testing if the fuel volatility portion fails. I know that used to be part of the monitors diagnostic criteria. If the fuel is not overly volatile perhaps the tank pressure sensor could be…

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Bob Owner/Technician
Massachusetts
Bob
 

Craig, What happened was when I shut the car off after a road test, i heard the evap vent valve shut while I was still sitting in the car. I pulled up evap data and I could see the vent was shut and pressure was rising which tells me there is NO evap leak. Keep in mind this is with the ignition OFF. After a minute or so the vent opened and the PCM went to sleep. I expected to see mode 6…

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Craig Technical Support Specialist
Illinois
Craig
 

Robert, I wonder if that was a P0440 large leak test or fuel cap test running and the natural vacuum portion of the testing is what's failing. I have seen small pass/small fails hold up monitors on Ford vehicles. The mode 6 data would show large leak information but small leak data wouldn't be populated with data just zeros.

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Bob Owner/Technician
Massachusetts
Bob
 

A large leak test is done with the engine running. The test I witnessed was with the key off.

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Jamey Owner/Technician
California
Jamey
 

I’m sure you checked this Bob, but just in case. Make sure the IAT and ECT are within 8* or less on a cold start. I didn’t look up the criteria, but I think 8 is about right. Also, I think low Key on voltage or not enough charging system voltage on start up can suspend the monitor. I do not believe the permanent code will keep the monitors from setting. I run monitors on a regular basis and have…

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Craig Technical Support Specialist
Illinois
Craig
   

Jamey, I didn't think of voltage battery SOH being used as a EONV evap disable criteria but I see the reasoning. Thanks for bringing it up I will have to research that and add that to my list of monitor disabling items. Craig

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Jamey Owner/Technician
California
Jamey
   

I had a Corvette that would not run the Air Injection monitor because the customer put in a cheap dime store alternator. It would not charge for about 3 or 4 minutes after start up. I connected my battery charger that I use for programming and dialed up 13.7 volts. I started the car and turned on the charger. Monitor ran first try. He had been fussing with it for over 2000 miles. It set a code…

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Bob Owner/Technician
Massachusetts
Bob
 

Yes, I checked at koeo before startup. They all agree.

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Bob Owner/Technician
Massachusetts
Bob
 

Charging voltage is 14+

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Sean Educator
New York
Sean
 

It conversion very difficult to get it to run evap I’ve had the same problem If it’s a matter of getting the job done still the fuel tank as full as you can get it run it and it was very often skip over the evaporative emissions test It will run the O2 test and allow you to inspect it because it will only have one monitor not ready. I don’t know if you’re looking for a repair solution or an…

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Bob Owner/Technician
Massachusetts
Bob
 

I'm not trying to prevent any monitor from running. I'd be happy if they completed and failed because at least then I would have a code.

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Sean Educator
New York
Sean
 

OK you stated the problem was getting it through the emissions inspection if you get it through the emissions inspection then do you have all the Time in the world to drive it and when that evap monitor finally kicks a code you’ll have it.

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Bob Owner/Technician
Massachusetts
Bob
 

Emissions inspection is the customer complaint, getting them to complete is my monkey.

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Philip Educator
California
Philip
 

Bob, You probably know this, but just in case: Go to Mode $09, in use performance tracking, just to see how often the O2 and EVAP monitors have run. At least it will give you some idea about the number of times in the past this vehicle has managed to run those monitors to completion. “Conditions” is some weird CARB OBD thing that has been explained to me several times without my comprehension…

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Sean Educator
New York
Sean
 

Exactly I’ve seen a few of them like that. And there’s no way you can charge the customer for all that time chasing a monitor . Over here in New York it’s a customers complaint is if they want an inspection then you only run the monitors that are required to be done for the inspection and return the car to the customer and pre-complaint status Anything you do further than that is just donated time

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Bob Owner/Technician
Massachusetts
Bob
 

Well Phil, you're probably right that I have been banging my head against the wall. I looked at this data but didn't really give it enough thought. The strange thing is that it shows Zero completions on the Cat monitor but it does complete the cat Mon and it passes. If I can't reflash the PCM then I guess the only option is replacement? Here are some snapshots. Wednesday Thursday Friday

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Randy Diagnostician
Colorado
Randy
 

There is nothing wrong in this data. Are you concluding it needs an ECU based off of something here? or did I misunderstand your comments. Disconnecting the battery may reset IUMP which is what it looks like you did. If you didn't, then it's losing power. It can be normal for the numerator to show 0 completions and the readiness flag complete. I have numerous examples of this.

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Bob Owner/Technician
Massachusetts
Bob
 

I'll admit I don't understand this data as well as I should. I found it odd that the Cat monitor shows as never completing yet it does. You're saying that's normal? I did do a battery disconnect.

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Randy Diagnostician
Colorado
Randy
 

It is odd but normal. Some vehicles more than others.

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Brad Diagnostician
Washington
Brad
 

Why not use the scan tool and do a service bay test for the EVAP system and see if it sets a code or passes?

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Bob Owner/Technician
Massachusetts
Bob
 

I thought of that but it's not available on this car. It does run the purge and seal test just fine.

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Brad Diagnostician
Washington
Brad
 

Good to know, I guess I haven't ran into one that didn't have the test in it? We have had issues with both purge and vent valve not sealing under vacuum but when testing with pressure (EVAP station ) 13" H2O it will show good. The P0442 can be tough to find cause on the service station it will pass the small leak (.020 in) but failure under vacuum.

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Craig Technical Support Specialist
Illinois
Craig
   

Brad, I stopped using a smoke machine using pressure to test evap systems a long time ago. I have been burned by that method far too many times as well as watching others wasting tons of time looking for smoke that never shows. Presently I use a Dwyer Instruments manometer, a 0-10 inch water column gauge I usually go right to the canister and test one is to disconnect and test the evap purge…

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Thanks
Randy Diagnostician
Colorado
Randy
 

It sounds like at least some are running, the issue is the readiness flag is not setting to complete. With that assumption, I need OBD data posted to go any further. Did you perform a complete OBD scan and record the data? Can you post it?

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Bob Owner/Technician
Massachusetts
Bob Update
 

The ecm part number I pull from the scanner … appears to be wrong for this car. On the ecm tag it shows a service # … which is what comes up in Repair Link for this vin but it also shows the … part number. I'm looking at a mismatched ecm aren't I? Ecm

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Brad Diagnostician
Washington
Brad
 

The ECM that is in the picture is correct for the VIN that you supplied at the top of the page.

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Phil Technician
Massachusetts
Phil
 

I don't really bother with Evap typically because it is too difficult to run. Later GMs are much more difficult with the o2 monitors. Evap codes will typically block the catalyst monitor from running on GM, but a permanent DTC should not do that. I wouldn't try clearing codes anymore. Run a few drive cycles and then go into GM enhanced-→codes-→additional DTC information-→Not ran since codes…

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Randy Diagnostician
Colorado
Randy
 

I agree. I left off the DTC pull you mention here because he disconnected the battery but that's the fastest way on a GM before clearing DTCs. I got a program setup to pull GMLAN DTC status that's really fast but I haven't written the end user display so it just dumps it into a spreadsheet which is not easy to read. Maybe I will get back to that project someday. We get those 4 DTCs as well.

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Phil Technician
Massachusetts
Phil
 

I must have responded no less than 10 times to folks about using that method both here and at the other site which shall not be named. Never seem to get any responses to it though. I'm not sure if folks don't believe in it, or won't bother trying it. It's kind of weird. I'm not including Bob in this group, I am sure he will be along in a day or three with an update. Do you find folks receptive…

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Randy Diagnostician
Colorado
Randy
 

>Do you find folks receptive to this that you talk to Randy? No. Locally, it's a tough sell over the phone. One thing I have come up with is to not tell them what to do but to tell them where to drive knowing they will naturally do what I need them to do. BTW, don't worry about credit for me I doubt I came up with anything that someone else hadn't came up with before.

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Mark Diagnostician
Indiana
Mark
 

yes, that is what I come across too, the rear o2's. I found that shifting down a gear for the decels help get DFCO to occur, which is the primary goal for the rears.

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Timothy Mechanic
Pennsylvania
Timothy
 

Good morning Phil, Would this be the same as going to DTC status using the Tech2? That is what I do when running monitors on GM vehicles, but I'm wondering if I'm missing another good tip.

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Phil Technician
Massachusetts
Phil
 

It's been awhile since I had a Tech2 in my hands Tim. Is that the menu that shows all of the codes on startup and then they start disappearing as the various diagnostics run? Same way to approach the problem using that way or the not ran since code cleared way. Basically you are trying to complete the o2 monitor. Look for any o2 related codes that haven't run yet. Once they are found look them…

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Timothy Mechanic
Pennsylvania
Timothy
 

Phil, Yes, that's the menu - so basically the way you monitor it, and the way I monitor it, are the same thing. That's a good way to go, I just wanted to make sure I wasn't missing another option that I should be aware of. Thanks,

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Randy Diagnostician
Colorado
Randy
 

There are multiple ways to see DTC status and depends on the scan tool the tech is using, some are better than others. Basically, it's an A9 request and can be a sub function 80, 81 or 82. What I do is the sub function 81. The next hex is for bit 0 - 7. In the picture below I select bit 2 (04 in hex) for test not passed since DTC cleared. You can see the bits across the top of the chart. All…

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Timothy Mechanic
Pennsylvania
Timothy
 

Hi Randy, I believe the Tech2 only shows Status by DTC, and that's what I'm usually using. I'll need to play around with a few other scan tools and see what I can find. Thanks

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Phil Technician
Massachusetts
Phil
 

The only problem with doing it your way versus my way is that the DTC status list resets every time the key is cycled. Not ran since codes cleared is a history of codes not run since the last PCM reset. The only advantage to your way might be on a roadtest because your list of codes is updating live as you drive the vehicle. I am unsure if the NRSCC list of codes will update live during a…

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Timothy Mechanic
Pennsylvania
Timothy
 

You're right, and that's a good idea. I just completed monitors on a Buick and using the Tech2, the Not Ran Since Codes Cleared does update live while driving.

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Phil Technician
Massachusetts
Phil
 

Thanks for checking on that, good to know it updates in real time.

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Bob Owner/Technician
Massachusetts
Bob
 

Phil, I did take a quick look at the “not run” codes and there were many, including the ones you mention. Sadly I didn't save them. I gave the car back to the shop i'm doing this diag for and told them to drive it over the weekend. I will check back and see if they were able to get the O2 mon to run.

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Paul Mechanic
Illinois
Paul
 

A couple of things come to mind. First, I've noticed late model GM's have been hard to set O2 monitors and I have had a few that seemed like they wouldn't set to ready until EVAP set. I thought I read somewhere that the newer GM's run the O2 monitor after warm cycle. Not sure exactly what you have tried, but try driving it and after reaching operating temperature, let it hot soak for about…

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Scott Owner
California
Scott
 

Hi Bob, The way I approach this is - Do a search for "I/M", I'm using GM SI. For this particular vehicle the first item that comes up is - Inspection/Maintenance Complete System Set Procedure Document ID: 2221382 Of interest is to open the hood - Inspection/Maintenance (I/M) System Set Procedure  1. Ensure that the vehicle meets the conditions for a cold start listed above. ⇒ If the EVAP…

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Phil Technician
Massachusetts
Phil
 

In Massachusetts we are allowed one monitor to be NR on an initial inspection, doesn't matter what monitor it is. On a reinspection after a failed inspection the same rules apply except for the catalyst monitor. If the vehicle fails an inspection for a catalyst DTC, then upon reinspection the catalyst monitor must be ready. We have to allow the one monitor NR because if we didn't we would have…

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Bob Owner/Technician
Massachusetts
Bob
 

Thanks for the information Scott. I did have that document and followed it to the letter. Even thought the evap status was YES it still wouldn't run. I wish I would have spent a little more time looking at the Not Run Since codes. It probably would have helped. I was looking at this for another shop. At the moment the customer is driving the car. If I see it again or get any updates I will…

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Randy Diagnostician
Colorado
Randy
   

Bob, I understand you posted more for discussion than a fix based on your original post. I'll try and give some discussion points that may or may not help. A monitor is only for a single DTC. Readiness flag is for a group of DTCs (monitors). Saying the monitors aren't running is misleading. When a monitor runs it will result in either a pass, fail, or no decision. Just because you don't see a…

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Bob Owner/Technician
Massachusetts
Bob
 

Randy, Thanks for a very concise explanation. I definitely need to spend more time looking at that code/criteria data. I have looked at it briefly on other cars but I never really dug into it because I haven't had this much difficulty completing monitors until now. I may not get another crack at this car but it's great to have a better understanding of this process for the next one.

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Bob Technician
Massachusetts
Bob Resolution
 

UPDATE - RESOLUTION This vehicle has finally run and passed all it's monitors. The customer took the car and drove it for a few weeks. Brought it back for us Monday 2/15/21 for a recheck. I hooked up my escan and it showed all monitors complete and no codes. She took it for a sticker and it passed so she is now happy, and so are we. I tried to upload the report file but the system won't accept…

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Mark Owner/Technician
California
Mark
 

What a great analysis. Thanks Randy, Bob, Craig, Phil, Phil, Jamey, Scott, Paul and Brad.

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Paul Mechanic
Illinois
Paul
 

Just had another late model GM-2015 Encore and trying to set enough monitors for an emission test. Needed either O2 or EVAP to pop. Let it sit two nights for a cold start the next day. O2 was always enabled, but EVAP never would enable with vehicle running-KOEO enable would read yes, but the moment it was started, enabled read no. Tried what I suggested to you about warm start for O2 monitor…

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