Snapon Diagnostics Product Forums Diagnostic Home . Diagnostic Product Index . Customer Care        
Diagnostic SoftwareDiagnostic PlatformsAsk-a-Tech, Automotive Repair InformationTech Central
Go Back   Snapon Diagnostics Product Forums > Member General Discussion Forum > General Discussions > Evaporative (EVAP) Emissions Systems
Home Today's Posts Register Members List FAQ
Thank you for visiting Snap-on Diagnostics Product Forums.
You are currently NOT logged in to a registered account. Some functions of Snap-on Diagnostics Product Forums will not be available to you if your are not logged in as a registered member. For a limited time only, registrationto Snap-on Diagnostics Product Forums to Snap-on Diagnostics Product Forums is !! FREE !! Select the    **REGISTER NOW**    link to register for your FREE Snap-on Diagnostics Product Forums account!!

Reply
 
Thread Tools Display Modes
  #1  
Old 07-07-2012, 05:23 AM
Bob's Garage's Avatar
Bob's Garage Bob's Garage is offline
Senior Member
 
Join Date: Nov 2007
Location: Waukegan IL
Posts: 3,245
Bob's Garage Made it to level 2!  Looks like you are on your way to becoming famous

Default Frustration with GM EONV testing

Anyone with any insight, please feel free to comment.

This vehicle came from another shop, complaint is that it won't run monitors fo the IEPA emissions test.

2007 Chevy Express Van 4.8 VIN V. G-2500 I believe.

When it came to me, the O2 Heater was ready, so, I knew it could set some readiness. It wasn't "forgetting" monitors either, due to a KAM problem . Later I find out that it sets a trans code, and the other shop would erase the code, which usually came up on a long drive.

So, with the O2 Heater already ready, I do the GM idle catalyst monitor right in my lot. OK, 2 out of 4 monitors ready! WTF!!?! Could it be this easy? I figure all I need to do is get it on the highway and run the O2 monitor, right? Forget about that. After a half hour, it sets a pending code for the trans and The O2 monitor never runs. GM O2 monitors have gotten very difficult in the last 8 years or so...

Well, since this is for another shop, I call them, but they say any trans repairs are out of the question. I say OK, then the Evap monitor is my only other chance.

This week we are in the high 90's and over 100F part of this week, so GM EONV is not able to run above 85F. So, I turn on the AC in the shop and let her "cold soak".

I get out my Tech2 check fuel at 21% and after a few attempts, I get the engine running portion of the ESBT test to run and I am directed to drive 9 miles and 800 seconds, so I do, keeping the trans from straining and slipping. The trans code did not reset.

I finish the driving portion and The Tech2 directs me to "return to Service Bay" to begin the engine off portion. I shut the vehicle off and this message come up:

2012-07-06 Tech2 EONV test denied 2007 Express 4.8 001.JPG

Does anyone know more about the fuel level requirement? I saw 15-85% as the requirement for this vehicle's EONV testing in Alldata.

All I can think of is that the fuel level slips below 15% during the drive? I started with 21% and it shows 19%. This is a large fuel tank, very large, near 60 gallons I think.

Until I can get this squared away, I don't see this thing passing soon. I did add more fuel, but I suspect a bad fuel level sensor because it doesn't want to take over a few gallons and kicks the fuel fill nozzle off at the gas station. The vent valve is not stuck, and it passes the Engine running part of the test.

Thanks, Bob




Last edited by Bob's Garage; 04-04-2015 at 04:38 AM..
Reply With Quote
  #2  
Old 07-07-2012, 05:53 AM
sandt38 sandt38 is offline
Senior Member
 
Join Date: May 2012
Location: NC
Posts: 186
sandt38 Made it to level 2!  Looks like you are on your way to becoming famous

Default

Yeah, 15-85% by my literature as well.

Slosh might be an issue, but think about how many fuel level senders you have replaced on GMs over the years. Is it possible you have an issue on the sweeper?
Reply With Quote
  #3  
Old 07-07-2012, 06:00 AM
Bob's Garage's Avatar
Bob's Garage Bob's Garage is offline
Senior Member
 
Join Date: Nov 2007
Location: Waukegan IL
Posts: 3,245
Bob's Garage Made it to level 2!  Looks like you are on your way to becoming famous

Default Level sensor innaccurate?

Quote:
Originally Posted by sandt38 View Post
Yeah, 15-85% by my literature as well.

Slosh might be an issue, but think about how many fuel level senders you have replaced on GMs over the years. Is it possible you have an issue on the sweeper?
Yeah, I have noticed that the level will differ 2-3 % at times. So close, yet so far.
Reply With Quote
  #4  
Old 07-07-2012, 08:11 AM
Joe Rappa's Avatar
Joe Rappa Joe Rappa is online now
Snap-on DSD
 
Join Date: Aug 2007
Location: North Carolina
Posts: 1,819
Joe Rappa Made it to level 2!  Looks like you are on your way to becoming famous

Default

While GM states 15%-85% in all their service literature, it is definitely not the case. I have seen a large number of them that simply wouldn't run over 75%. I've never had problems on the low end, but I won't try to run one there either. If you drive it, and it goes below 15% during the road test, it aborts. At least your tank is low, so you can add some. It's more of a pain when they are too full.

Joe
__________________
"You don't build a reputation on what you're going to do"
Henry Ford
Reply With Quote
  #5  
Old 07-08-2012, 06:08 AM
Bob's Garage's Avatar
Bob's Garage Bob's Garage is offline
Senior Member
 
Join Date: Nov 2007
Location: Waukegan IL
Posts: 3,245
Bob's Garage Made it to level 2!  Looks like you are on your way to becoming famous

Default

Quote:
Originally Posted by Joe Rappa View Post
While GM states 15%-85% in all their service literature, it is definitely not the case. I have seen a large number of them that simply wouldn't run over 75%. I've never had problems on the low end, but I won't try to run one there either. If you drive it, and it goes below 15% during the road test, it aborts. At least your tank is low, so you can add some. It's more of a pain when they are too full.

Joe

Hi Joe and all,

Thanks for the info. Well, fuel level was most likely one of the issues. It really sucks that it waits until the whole engine running test and 10 mile drive is over to inform you.

I did get some more fuel into the tank, so that it was 23% or so.

2012-07-07 Tech 2 shots 2007 Express Van EONV 001.JPG

I cooled it off all night (again) but the ECT was at 89F in the morning, so I did a trick I have done for years, I carefully aim a small stream of water right at the coolant sensor and cooled it down to a usable 82F. I never do this on a hot engine unless it has cooled down for a while on it's own or I may put a fan over the engine for a couple of hours.

I'm not sure what happened since yesterday, but the test aborted to a "vent system malfunction" so, back to square one.

2012-07-07 Tech 2 shots 2007 Express Van EONV 004.JPG

I did the purge and seal and sure enough, I get close to 20mm hg vacuum at 30% purge with the vent open! This shot was during the ESBT, 14% Purge 15mm hg with the vent open, I was sure the test would abort:

2012-07-07 Tech 2 shots 2007 Express Van EONV 005.JPG


I had already put a new Vent solenoid on. The old one was stuck wide open, no P0449, just stuck open.

Knowing the other vent path restriction could be in the canister, I removed the canister. It was heavy and takes some effort to blow through it (not a reliable test). I took light shop air and just gave it a blow each way through the large ports, but that will not do much, but it did allow me to run the ESBT again to completion:

2012-07-07 Tech 2 shots 2007 Express Van EONV 007.JPG


With the ESBT done, I quickly ran the the driving portion. Funny thing, I had to drive it a mile past the zero mile point (time was expired). I finally get the "Return to service bay" message, so I pull back in my lot.

2012-07-07 Tech 2 shots 2007 Express Van EONV 008.JPG


OK, Key off portion. Still 23% fuel, I'm good. The test runs to completion ! !



2012-07-07 Tech 2 shots 2007 Express Van EONV 017.JPG


With a failure of course. P0442, which is GM's way of saying I have a very, very small leak (which should be a P0456 not a P0442) that may be hard to find. Ha-Ha!


2012-07-07 Tech 2 shots 2007 Express Van EONV 018.JPG


Well, it is time to call the other shop. Let's see. R & R canister, new vent solenoid, several attempts at setting readiness, fuel filling, cool down in shop with AC on, reprogramming, but the stated goal is now complete. Get the monitors ready. How many hours? Can they pay? Can thier customer pay?

At least this week, the temps will be lower so more EONV attempts can be made without extra cooling and time spent there.

If they want to pay...

Thanks, Bob
.

Last edited by Bob's Garage; 07-08-2012 at 09:23 PM..
Reply With Quote
  #6  
Old 07-08-2012, 01:43 PM
sandt38 sandt38 is offline
Senior Member
 
Join Date: May 2012
Location: NC
Posts: 186
sandt38 Made it to level 2!  Looks like you are on your way to becoming famous

Default

I suspect you may have lost a little hair on this one.
Reply With Quote
  #7  
Old 07-09-2012, 03:49 AM
Crusty Crusty is offline
Senior Member
 
Join Date: Dec 2007
Location: Great White North
Posts: 2,407
Crusty You made it!  You've done a great job ofearning reputation from your peers.  You now have secret access to a new hidden forum!

Default

While MOST GM's state the fuel tank level must be BETWEEN 15% and 85% (really meaning it must be 16% to 84% inclusive), that is not the case for ALL GM vehicles. I've looked at a great many code descriptions and there are some that require 26% and others 21%, and yes, fuel slosh can be a factor.
The fuel tank level volts pid doesn't show the second decimal point but the ECM definitely looks at the fuel level voltage signal to more than one decimal point so it can tell the difference between 43 and 44 percent.
This is why the fuel tank level percent is a critical pid that is missing on lots of GM vehicles in the SO scan tools.
AT LEAST THE TECH-II TOLD YOU IN THE FIRST PLACE THE FUEL LEVEL WAS AN ISSUE INSTEAD OF JUST SAYING "ABORT" LIKE THE SO SCANNERS DO-!!
So, you need more fuel in the tank. The tank won't fill properly. Usually an issue with the venting capability of the tank. Usually a blockage somewhere, anywhere the tank expects to be able to allow vapours to escape to, which is not necessarily just the fill vent tube up the neck, but also the evap-vent valve and the canister and the related tubing & pies.
There are some TSB's regarding the vent valve location on many GM light trucks. There may be one that applies to this van. I personally have seen more vent valve issues than purge solenoid issues on GM's as they're usually located where dirt & grit can enter the system.
So, once you got a little more fuel in the tank, the fuel level didn't cause the system to abort the self test. It did however find some kind of issue with the venting system (and all that encompasses)
It selected P0442, and the P0456 may be for a gross leak (such as a gas cap) but some of the codes have changed the descriptor where one code is for a small leak and another is for a VERY small leak, so look up the individual code for that specific vehicle and don't just go from memory. (sorry, don't have my data base here at home so i can't check it right now)
Sometimes there is one sentence, or one word, or one pid value that is different than the previous year or similar model vehicle.
The evap self test (without commanding the evap SBT) will run if the vehicle has an engine off time longer than 17 hours. (ANOTHER critical pid that is quite often missing from SO datastreams). Look at the "conditions for running the code" under P0442, P0446, P0456 and P0496 (I'm just going from memory here but there is a chart for which codes are related to which "monitor")
Usually a drive cycle, while recording the datastream with a SO scanner, will take a little more time initially, but it will also allow you to play back the activity with more detail in a graph than the Tech-II will show, and it can be very easily manipulated if you play the movie back in SSC (just don't get confused with the SSC messing up the decimal point location-ROFLMAO)
You could also look at the chart for the "monitors" and see which codes are related to the oxygen sensor testing and check those related codes.
Check each code individually and see which ones ran and which ones didn't. It will also show which ones passed and which ones failed. (you can check each code for both the EVAP system as well as the O2 sensors and there may be 8 or 10 codes related to those monitors but you may only have one code not being satisfied in each of the two monitor systems)
Sorry for the long post but you asked......LOL
HTH
Reply With Quote
  #8  
Old 07-15-2012, 09:04 AM
Trindaddy's Avatar
Trindaddy Trindaddy is offline
Senior Member
 
Join Date: Jan 2010
Location: New Hampshire
Posts: 337
Trindaddy Made it to level 2!  Looks like you are on your way to becoming famous

Default

AC in the shop!...Oh how I wish I had the money for that.
Reply With Quote
  #9  
Old 08-04-2012, 05:00 AM
Bob's Garage's Avatar
Bob's Garage Bob's Garage is offline
Senior Member
 
Join Date: Nov 2007
Location: Waukegan IL
Posts: 3,245
Bob's Garage Made it to level 2!  Looks like you are on your way to becoming famous

Default Evap monitor ready with no codes, passed emissions.

Sorry about the long delay on this now fixed vehicle, it had to go through another shop and a very hesitant customer looking for a gauruntee that this vehicle would pass if he spent the money. I told my customer (another shop) that since I was a sublet, he had to mark-up the repairs for it to make good business sense. I also told him that if for some reason we had no success that would return all parts, but I was confident.

I ordered a new evap canister and installed it. The high temps had dropped down into the mid 80's F so I knew I was able to make a few attempts to run the SBET a day. As it turns out, I needed only one attempt. It passed EONV and I took it to the IEPA emissions test and got my passing paperwork.

Apparently the canister was restricted enough to make the PCM think that the FTP was not seeing enough vacuum fast enough, setting the P0455 originally and then going to the P0442 after blowing shop air through the canister. I am happy to say that I was able to run this EONV 2 more times also just to confirm. I never did see the O2 monitor pass, but the requirements to set readiness on that would cause a trans code to set. So, thanks to EPA laws allowing one monitor to not be ready, the unoticeable "slipping" in the trans can be ignored for now.

Thanks to Crusty, Joe and Sandt for your input.

Bob
Reply With Quote
  #10  
Old 08-12-2012, 05:26 PM
Crusty Crusty is offline
Senior Member
 
Join Date: Dec 2007
Location: Great White North
Posts: 2,407
Crusty You made it!  You've done a great job ofearning reputation from your peers.  You now have secret access to a new hidden forum!

Default

Glad you got it fixed.
A particular REQUIREMENT for ANY EVAP testing is the fuel tank level PERCENT to be within the specified range.
Sadly, SnapOn doesn't include that pid in ALL the GM vehicles, even though it IS IN the datastream as evidenced by extensive cross-checking with the Tech-II.
Such a basic pid REQUIREMENT and it's MISSING-!!
Your testing & diagnosis PROVES the NEED for BASIC PIDS to be included whenever the manufacturer has it in their tool.
Good work Bob. Cause & effect-basics.
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -7. The time now is 03:44 PM.


Reminder: Your participation in these areas of the site is solely at your own risk. The
information is only the opinion of the poster, is no substitute for your own research,
and should not be relied upon for business critical decisions or any other purpose.
Never assume that you are anonymous and cannot be identified by your posts.
We reserve the right to discontinue any users' use of any such public forum
for any reason. Please read the Terms of Service.

Snap-on is a trademark, registered in the United States and other countries, of Snap-on Incorporated. Other marks are marks of their respective holders.
©2009 Snap-on Incorporated. All rights reserved.