EVAP season is just about here

[Crusty]

With this being March, ambient temperatures in most of the US & Canada start to climb to the minimum ambients required for systems to perform EVAP self diagnostics and thus spring & fall are the most prevalent times of the year we see evap failure codes.
The systems just won't self test in the cold of winter, nor the high heat of summer.
While it may be obvious to some, it may not be obvious to others that there are pids that we need to monitor in order to PROPERLY test evap system failures.
This is from an article that was speaking of an import vehicle evap system but it is still true for almost any vehicle I have encountered or read about.

"The quickest way to run any monitor is to control as carefully as
possible the critical enabling criteria of road speed, fuel level and coolant
and air intake temperature."

Kinda hard to control those parameters if we can't see the pids so we know what the ECM/PCM is seeing and thus what it is going to try to do.

[Orevin]

With this being March, ambient temperatures in most of the US & Canada start to climb to the minimum ambients required for systems to perform EVAP self diagnostics and thus spring & fall are the most prevalent times of the year we see evap failure codes.
The systems just won't self test in the cold of winter, nor the high heat of summer.

There is an EVAP season? I see EVAP problems pretty much every day, summer, winter, full moon... doesn't matter.

While it may be obvious to some, it may not be obvious to others that there are pids that we need to monitor in order to PROPERLY test evap system failures.
This is from an article that was speaking of an import vehicle evap system but it is still true for almost any vehicle I have encountered or read about.

"The quickest way to run any monitor is to control as carefully as
possible the critical enabling criteria of road speed, fuel level and coolant
and air intake temperature."

Kinda hard to control those parameters if we can't see the pids so we know what the ECM/PCM is seeing and thus what it is going to try to do.

These pids are available, but should be displayed together with other crucial data like FTP, purge and vent status.

I agree with others that call for a list that contains all available pids, so we can look at what ever data we deem to be important. Autoenginuity works that way and I like it a lot!

[Crusty]

There is an EVAP season? I see EVAP problems pretty much every day, summer, winter, full moon... doesn't matter.



These pids are available, but should be displayed together with other crucial data like FTP, purge and vent status.

I agree with others that call for a list that contains all available pids, so we can look at what ever data we deem to be important. Autoenginuity works that way and I like it a lot!

Which vehicle manufacturer DOESN'T consider temperatures for EVAP self tests??
When it's minus 20-C, every one I've looked at will not run the complete series of evap self tests and will either abort or suspend the tests.

[Glenn Richardson]

Which vehicle manufacturer DOESN'T consider temperatures for EVAP self tests??
When it's minus 20-C, every one I've looked at will not run the complete series of evap self tests and will either abort or suspend the tests.

If a Toyota key-off system (starting June 2005) is parked in a garage it could and would run the monitor if the garage is warm enough. This system runs the monitor 5 hours after the key is turned off. Other EONV / ESIM systems could run the monitor also. In the future more of them will run. Get ready!

[Crusty]

If a Toyota key-off system (starting June 2005) is parked in a garage it could and would run the monitor if the garage is warm enough. This system runs the monitor 5 hours after the key is turned off. Other EONV / ESIM systems could run the monitor also. In the future more of them will run. Get ready!

Yes, some run the self tests hours after shut down. Can you elaborate on which ones run hours later? If the Toyota was outside in minus 20-C temperatures, would it run then?? Can you cite an example of YY/MM/MM for further reading & investigation?
Some 07, 08 & 09 GM's run the evap monitor after a cold start, run cycle, they have to reach temperature and also travel a number of miles before the self test will run, I think it's about 12 miles?? The ECM/PCM stays powered up for as much as 40 minutes after shut down, even with the key out and the doors locked if the vehicle has just met the enable criteria on that start/run cycle.
But do ANY systems NOT take into account temperatures, either ambient or running temperatures? I can't find any that totally ignore temperatures.

[Glenn Richardson]

Yes, some run the self tests hours after shut down. Can you elaborate on which ones run hours later? If the Toyota was outside in minus 20-C temperatures, would it run then?? Can you cite an example of YY/MM/MM for further reading & investigation?
Some 07, 08 & 09 GM's run the evap monitor after a cold start, run cycle, they have to reach temperature and also travel a number of miles before the self test will run, I think it's about 12 miles?? The ECM/PCM stays powered up for as much as 40 minutes after shut down, even with the key out and the doors locked if the vehicle has just met the enable criteria on that start/run cycle.
But do ANY systems NOT take into account temperatures, either ambient or running temperatures? I can't find any that totally ignore temperatures.

Chry--NVLD (2003 to 2007) and ESIM (2007 to today) both test a long time after shutdown. ALL EONV (GM starting 2002) and (Ford starting 2005 on F-250's)and others can start 10 to 30 minutes after shut down. Kia starting in June of this year is coming out with a new system (key off NVLD) that will test after shut down. I see them almost ALL going that way. When a person say testing EVAP and talk about the EVAP monitor there is other test that goes on that can set EVAP code -- On a hot or cold day! P0446 - P0457 to start with. P0446 The FED law says that the OEM must prove that purge occurred when purge was commanded. This is sometime a mistake for the PCM and it sets a P0455 by mistake with NO leak at all. AND NOT completeing the monitor. I have seen this happen myself (rental car) on a cold day. Also I showed this to a writer for Motor magazine (Mark Warren) and he wrote an article on this subject. ALSO gascap code P0457 I have seen also after refueling on a cold day. GOing home for the day I hope this helps.

[Crusty]

Chry--NVLD (2003 to 2007) and ESIM (2007 to today) both test a long time after shutdown. ALL EONV (GM starting 2002) and (Ford starting 2005 on F-250's)and others can start 10 to 30 minutes after shut down. Kia starting in June of this year is coming out with a new system (key off NVLD) that will test after shut down. I see them almost ALL going that way. When a person say testing EVAP and talk about the EVAP monitor there is other test that goes on that can set EVAP code -- On a hot or cold day! P0446 - P0457 to start with. P0446 The FED law says that the OEM must prove that purge occurred when purge was commanded. This is sometime a mistake for the PCM and it sets a P0455 by mistake with NO leak at all. AND NOT completeing the monitor. I have seen this happen myself (rental car) on a cold day. Also I showed this to a writer for Motor magazine (Mark Warren) and he wrote an article on this subject. ALSO gascap code P0457 I have seen also after refueling on a cold day. GOing home for the day I hope this helps.

Yup. I'm aware of the Dodge NVLD.
""ENABLING CONDITIONS TO RUN EVAP LEAK DETECTION TEST
1. Cold start: with ambient temperature (obtained from modeling the inlet air temperature sensor on passenger vehicles and the battery temperature
sensor on Jeep & truck vehicles) between 4° C (40° F) and 32° C (90° F) for 0.040 leak. Between 4° C (40° F) and 29° C (85° F) for 0.020 leak.
2. Engine coolant temperature within:-12° to -8°C (10° to 18°F) of battery/ambient.
3. Battery voltage between 10 and 15 volts.""

I've been reading up on Fords too.
""1. The enhanced EVAP system uses inputs from the engine coolant temperature (ECT) sensor or cylinder head temperature (CHT) sensor, the intake
air temperature (IAT) sensor, the mass air flow (MAF) sensor, the vehicle speed and the FTP sensor to provide information about engine operating
conditions to the PCM. The fuel level input (FLI) and FTP sensor signals are used by the PCM to determine activation of the EVAP leak check
monitor based on the presence of vapor generation or fuel sloshing.""

Do ANY manufacturers NOT take into account temperatures??

[Skip]

Are you guys going to start arguing about global warming next?
Yes, they all look at temperature but not evrybody has sustained ambient temperatures that are out of range to run the monitors. Where Crusty lives it's a seasonal issue. Where I live, it got so cold this winter I had to scrap a thin film of ice off my windshield one morning. Brrrrrrrr.

Crusty, thanks for pointing out something not everybody may have thought of but I have to honest, my first thought was "evap season?"

[Bob's Garage]

Evap season

Yes indeed,

There is an Evap season. My contact at IEPA has stats that show that April and May are the biggest months for Evap code failures.

I think what Kai was alluding to is, here in the Chicagoland area we do seem to fix a lot of Evap codes even in winter. But, you know how customers are. They clear the codes and evap monitors don't go ready and sometimes they get lucky and pass with the evap monitor not ready.

But in most cases, the unlucky customers avoid the test for so long, they fail for evap codes in the dead of winter due to the fact that they really don't have the knowledge of code clearing and monitors etc, so that code that popped up in the last warm day of October is still there. That's why Kai (and I) do get a lot of Evap in winter.

The problem with Evap repairs is getting the monitor to run th verify the repairs. Of course then you are "off the hook" until April. In all cases I do what I have to do to get monitord to go ready for the sytem that I repaired.

I have learned a lot of tricks to get Evap monitors ready in winter, but that is another story.

[Crusty]

Hey Skip.
Oh Yes you do-! I doubt many evap monitors will run when it's 100-F in sunny southern California-!! You guys are just at the opposite end of the scale. January here is usually around zero fahrenheit. July we can get over 90-F.

You had to scrape your windshield ONE morning??? Heck, up here we WEAR OUT our ice scrapers every year-!
EVAP season?? YUP-!!
Just like Battery season.
More batteries get sold in the winter months than other times of the year. This happens in the fall at my shop because I check & test customers' vehicles before they're dead in the driveway on a cold January morning.
---
Hi Bob
Winter salt, water, freezing, thawing, road dirt, corrosion play havock on vehicles (don'tcha know-!! LOL). The capability of evap systems is soooo sensitive, especially when you consider there is only about 13.6 or 13.8 inches of water column in ONE inch of mercury on the typical vacuum guage we've used on engine intake manifolds for years. The pass/fail thresholds written into the algorythyms in the ECM's is probably down to three decimal places.
The systems screw up over the winter and that doesn't show up until the ambient temperatures are within the enable criteria window (which I'm sure you understand, even if some in SO-CAL don't--LOL)
---
EVAP systems see the critical enabling criteria in the spring & fall in a large area of the continent, rather than in the dead cold of winter or the blistering heat of summer.

I would venture to say that 90% of intermittents are time &/or temperature sensitive too. Those are the FUN ones to figure out. We look for cause & effect. We know what the effect is, (it's running like dog poo), now what caused it??

The point is, ALL manufacturers consider temperatures and use the "Ideal Gas Law" which is based on Boyle's Law, Charles's Law, Kinetic theory, amongst others.
The basic premise is, vapour is a gas (not solid or liquid) and the EVAP systems are considering all of the variables that affect gas behavior.
To quote...."Gas Behavior.... The temperature, pressure, volume, and number of particles of a gas are all interrelated. Altering one of these quantities causes a change in one or more of the others"

Whether the system on any given vehicle is checking pressure or vacuum, and whether it is while the engine is running or after shut down isn't so much the issue (although understanding what each system is supposed to do is critical (RTFM-LOL)), we can't discern when the system has met all the "enabling criteria" for the monitors to run if we can't see the pids.

The same thing for any other "system" on a vehicle. We have to be able to look at the computer inputs & outputs to figure out what is going wrong and when it is going wrong.
We can check a whole bunch of things externally with meters, scopes & guages but some parameters are only available in the datastream that the manufacturers put there. Should we try to figure out a fuel trim percent?? Heck no. It's in the datastream (or should be) on the scanner.

We DIAGNOSE cause and effect.

While I do see more evap code sets in the spring and fall of the year, I repair systems at other times of the year too. How many decimal places do we have to test for on a fuel level input voltage to actually see what the critical input is, that the ECM uses to calculate whether the fuel level is at 84% vs 85%?? How about CTS 39-F vs 40-F?? Should we even have to??

The pids should be there so we can check and test for cause & effect, when the enabling criteria have been met, and the system migrates from testing, to failure or pass.

RTFS & RTFM-!! Basics. Obvious but often overlooked.

[Crusty]

Chry--NVLD (2003 to 2007) and ESIM (2007 to today) both test a long time after shutdown. ALL EONV (GM starting 2002) and (Ford starting 2005 on F-250's)and others can start 10 to 30 minutes after shut down. Kia starting in June of this year is coming out with a new system (key off NVLD) that will test after shut down. I see them almost ALL going that way. When a person say testing EVAP and talk about the EVAP monitor there is other test that goes on that can set EVAP code -- On a hot or cold day! P0446 - P0457 to start with. P0446 The FED law says that the OEM must prove that purge occurred when purge was commanded. This is sometime a mistake for the PCM and it sets a P0455 by mistake with NO leak at all. AND NOT completeing the monitor. I have seen this happen myself (rental car) on a cold day. Also I showed this to a writer for Motor magazine (Mark Warren) and he wrote an article on this subject. ALSO gascap code P0457 I have seen also after refueling on a cold day. GOing home for the day I hope this helps.

Glenn. Thanks for joining in. I'm sure your experience will help many of us.
Mark has several good articles. April-2010...June-2009....January-2005....
Bernie Thompson-March-2010....Jeff Masterman-May-2000
Dan Marrinucci has a whole series of EVAP articles running from January-2006 for several months.

Both Motor Magazine and Motor-Age Magazine are good sources of information. Underhood service is another and so is Import-Car, but the best is probably the factory service manuals which, while not perfect, are probably more often right than wrong and where we should look first for technical details as to how any vehicle "system" works.
If we don't know what it's supposed to do, how are we going to recognize when it's broken?

[Orevin]

Yes, there is a season when EVAP monitors run. And I'm aware of the requirements to make that happen.

A lot (well, most) of my customers don't care about a MIL. As long as the car is still moving and the AC is working, they will not show up at the shop. Until the vehicle fails at the emission test station and the registration can't be renewed.

As Bob stated, if the EVAP system fails during a warm day in Summer or Autumn and illuminates the CEL, the vehicle gets a fail at the test lane in January and shows up in my bay.

Another scenario would be a customer that parks his car in a garage. Let's say 50F inside, but 30F on the street. The monitor can still run, in the depth of Winter. Here is an example:

This 2001 Explorer was parked outside for a few hours when I decided to take it on a run to set readiness. IAT showed 45F when I hooked up the scan tool. I knew that value might drop below the 41F required for the EVAP (and CAT) monitor to run. However, the IAT is build into the MAF sensor and didn't wanna mess with it. So I took it out on the express way and the EVAP monitor ran, at 39F IAT:
2001_ford_explorer_40E_evap_run_good.jpg

The pids should be there so we can check and test for cause & effect, when the enabling criteria have been met, and the system migrates from testing, to failure or pass.

RTFS & RTFM-!! Basics. Obvious but often overlooked.

I agree, with both statements

[Glenn Richardson]

Glenn. Thanks for joining in. I'm sure your experience will help many of us.
Mark has several good articles. April-2010...June-2009....January-2005....
Bernie Thompson-March-2010....Jeff Masterman-May-2000
Dan Marrinucci has a whole series of EVAP articles running from January-2006 for several months.

Both Motor Magazine and Motor-Age Magazine are good sources of information. Underhood service is another and so is Import-Car, but the best is probably the factory service manuals which, while not perfect, are probably more often right than wrong and where we should look first for technical details as to how any vehicle "system" works.
If we don't know what it's supposed to do, how are we going to recognize when it's broken?

Thank you -- I'm sorry but I have been on the road and not been able to reply. Like I said from the begining this will happen (being on the road). Already I have enough air miles for my MVP status. I will be Gold by June.

I 100% agree with you on the articles that have been writen. (Good guys)

YES -- HOT -COLD--CODE---PENDING CODES-- and many other things play a big big part in running of the EVAP monitor. Also other problems you have already fixed has a BIG BIG part in running the monitor.

There is one word that sizes up our industry "CHANGE"

Lets see what the future bring!

[2004 Chevy 4x4]

Hello all, I have a question I'm sure you will have no problem answering in great detail judging by the rest of this thread. I have a 2004 chevy silverado with the 5.3 and I'm having vent valve issues. In the spring it threw a vent valve soleniod code several times and a small leak detected code once. Truck is running like dog poo and that is an understatement. It gets horrible gas milage and cannot climb the slightest grade without downshifting. I read that vent valve problems are common with these trucks, apparently if they are exposed to dusty environments they get clogged and stop working properly. GM's fix for this is to relocate a new valve above the transmission. Is this really necessary (very expensive and a pain to do myself)? If it took 140,000 miles to clog this one, by the time it gets close to 300,000 vent valves will probably be the least of its problems. The self test will not complete but the check engine light hasn't come on in months, perhaps what you were saying about temperature since it's hovering around 100. I know virtually nothing about emissions control but would like to learn all that I can. Any info you guys could send my way would be greatly appreciated.

[Crusty]

Hello all, I have a question I'm sure you will have no problem answering in great detail judging by the rest of this thread. I have a 2004 chevy silverado with the 5.3 and I'm having vent valve issues. In the spring it threw a vent valve soleniod code several times and a small leak detected code once. Truck is running like dog poo and that is an understatement. It gets horrible gas milage and cannot climb the slightest grade without downshifting. I read that vent valve problems are common with these trucks, apparently if they are exposed to dusty environments they get clogged and stop working properly. GM's fix for this is to relocate a new valve above the transmission. Is this really necessary (very expensive and a pain to do myself)? If it took 140,000 miles to clog this one, by the time it gets close to 300,000 vent valves will probably be the least of its problems. The self test will not complete but the check engine light hasn't come on in months, perhaps what you were saying about temperature since it's hovering around 100. I know virtually nothing about emissions control but would like to learn all that I can. Any info you guys could send my way would be greatly appreciated.

You got a lot of reading to do......That's what makes this trade so interesting.....the constant evolution and CHANGE mentioned before.
The long & short of your post is.....i don't think the "evaporative emission" system is where the core problems are with the truck in question.
The "evaporative emission system" is only part of all the emission systems on a vehicle. It controls fuel vapours from escaping to the atmosphere.
The fuel tank is sealed when shut down. The charcoal canister absorbs vapours when the vehicle is at rest. When the vehicle is started, the ECM will turn on the purge solonoid to purge the vapours out of the charcoal canister so it can absorb vapours the next time you shut the vehicle off.
In order to purge the vapours out of the charcoal canister, the vent valve is opened so fresh air can be drawn through the system allowing the vapours to be pulled out of the canister. If you don't let fresh air in, you can't pull fuel vapours out.
The ECM also opens the vent valve while the engine is running so as the fuel is pumped out of the tank, it doesn't create a vacuum that the fuel pump would have to work against.
Depending upon the enabling criteria for self testing (CTS, IAT, Fuel tank level PERCENT, and others), the ECM turns on the purge valve and closes the vent valve in a combination of sequences while it monitors the fuel tank vapour sensor (usually in the top of the fuel pump module assembly).
For example, if the ECM commands the purge valve on, draws vapour from the canister and vapours from the top of the fuel tank, and it opens the vent valve,.....only the vent valve stays stuck closed, it will create a vacuum at the wrong time. The ECM will see the INCHES of Water Column of the vacuum when it should see little or none. (an engine runs with about 18 or 20 INCHES of MERCURY on your normal vacuum guage. There are about 13.6 or 13.8 INCHES of WATER Column in ONE inch of mercury, so the vacuum values are very small)
If the system is self testing (again depending on the "enabling criteria"), and it commands the purge OFF and the vent closed, and it sees as vacuum created, it thinks the purge valve is leaking and pulling vapours even though it is commanded closed.
If the system is self testing, turns the purge on to pull engine vacuum on the system, and it commands the vent closed, and it doesn't see a vacuum created, it thinks the vent valve is stuck open, or has a leak.
Other makes/models will use a precalibrated vacuum diaphram/switch, that either commands a pressure or a vacuum, and watches for the diaphram/switch to change, either on or off at a precalibrated time. They're checking for leaks and system operational capabilities. The ECM/PCM knows what it commanded and wants to see an appropriate response at the correct time.
There's much more to the operational characteristics of the various and constantly changing systems........
THAT'S WHY IT IS SOOOOOO IMPORTANT TO SEE THE PIDS ASSOCIATED WITH THE SYSTEMS, all of which take into account both temperatures and fuel volumes.
Usually with a gas cap code, the ECM has seen a refueling event, guaged by the previous fuel tank level PERCENT and the current fuel tank level PERCENT.
Just had a Nissan Frontier set an evap code TWO DAYS and over a half dozen start/run cycles AFTER it was refueled, and AFTER the fuel tank level dropped to the appropriate fuel tank level for the "enabling criteria" to run the appropriate self test.

The GM bulletin relocates your vent valve, and/or the inlet filter location so the vent valve isn't exposed to quite so much dust/dirt causing it to stick either open or closed.
As with ANY bulletin or change from a manufacturer, the information MAY not be applicable to your vehicle. Your vehicle MAY benefit from the changes in the bulletin, but it may not solve the issues the vehicle has.
HTH