I guess they only do it once?

I wouldn't count on it.

 

I reset a lot of crashed srs modules for body shops

Couple of health problems ago I took airbags out of cars for a guy I know that owns a junkyard. All his guys were afraid to do it. But when I was working at Delphi they had airbags laying around in the department that made the harnesses for them, never saw one go off on it's own.

 

While we are on car troubles, I have one: 2000 Impala;

I have a 2003 Impala and the obd2 in those is the worse. Along with the TPS Strantor talked, about check all of your vacuum lines. The warm engine and going up a hill(engine moving around when under load) would have me checking them.

 

For air bags, disconnecting the battery is safest method and it only takes a few minutes to safely discharge. Air bags usually have shorting bars in the connector if I remember correctly for storage.
@strantor, before you look at major sensors as your problem, I would look at fuel injector cleanliness, fuel pressure, manifold vacuum and your ignition system in particular for failure under load. When was your last tune-up using OEM parts? When was the last chemical tune-up you did on your engine? Start with basics. If the light is not on, probably because the emission system is doing its job. If you have a scan tool, it will tell you a lot about what is going on and good ones will give you a scope pattern for sensors. KISS. Keep it simple Strantor

 

For air bags, disconnecting the battery is safest method and it only takes a few minutes to safely discharge. Air bags usually have shorting bars in the connector if I remember correctly for storage.
@strantor, before you look at major sensors as your problem, I would look at fuel injector cleanliness, fuel pressure, manifold vacuum and your ignition system in particular for failure under load. When was your last tune-up using OEM parts? When was the last chemical tune-up you did on your engine? Start with basics. If the light is not on, probably because the emission system is doing its job. If you have a scan tool, it will tell you a lot about what is going on and good ones will give you a scope pattern for sensors. KISS. Keep it simple Strantor

It's probably due for a tuneup but I doubt that's the cause of the codes I'm getting. These are not emissions codes, they're Evap codes. There's only a few things it could be. Leaky gasket on the fuel tank, bad gas cap (already replaced), bad filler neck, bad charcoal canister, bad purge valve (already replaced), maybe a couple of others. My money is on the charcoal canister or more likely the filler neck. It trips the backpressure mechanism in the fuel pump at most gas stations (as if the tank were full, when it's still empty). Most would say that points to the charcoal canister, but I suspect otherwise because I seem to remember there being a little spring-loaded stainless "door" inside my filler neck that gets pushed back when you insert the filler nozzle. It's not there. Maybe it never was; maybe I'm remembering another vehicle. But I think it was there, and if it was, and it's not now, then it must be lodged down somewhere in the filler neck. How that affects the Evap system I don't know, maybe I have more than one problem. Or maybe some dingus tried to siphon gas off my truck by jamming a length of hard pipe down my filler neck and not only broke off the flap door but also punctured a seal and now it leaks vapor.

 

These are not emissions codes, they're Evap codes

EVAP = evaporative emission control system .

 

My money is on the charcoal canister or more likely the filler neck. It trips the backpressure mechanism in the fuel pump at most gas stations (as if the tank were full, when it's still empty).

You don't say what vehicle this is in. The 2003 Impala my wife drives is bad about doing the gas pump shut down while filling thing. You can't just put the nozzle in and set the automatic fill lever. You need to hold it in just the right position and pull the nozzle trigger just the right amount to fill the tank without nozzle shutting off. The car when I bought it had some EVAP codes set and I fixed them but it still didn't stop the fill up shut down. I also had a 2004 Grand Prix a Pontiac version of the Impala, and it never had the problem.

 

EVAP = evaporative emission control system .

Ok fine LOL you win. But I'm pretty sure that right up until your mic drop, we had a common understanding that you were talking about exhaust emissions. You know, the kind associated with injectors, tune-ups, and that other stuff you mentioned which have no clear correlation to evaporative emissions.

 

That was @bwilliams60 passing on all that good info. I was just being a... ahem....educated donkey... joining in the conversation.

 

You don't say what vehicle this is in. The 2003 Impala my wife drives is bad about doing the gas pump shut down while filling thing. You can't just put the nozzle in and set the automatic fill lever. You need to hold it in just the right position and pull the nozzle trigger just the right amount to fill the tank without nozzle shutting off. The car when I bought it had some EVAP codes set and I fixed them but it still didn't stop the fill up shut down. I also had a 2004 Grand Prix a Pontiac version of the Impala, and it never had the problem.

2010 yukon. It hasn't always been this way. Used to not have a problem filling it.

 

That was @bwilliams60 passing on all that good info. I was just being a... ahem....educated donkey... joining in the conversation.

Oh my gosh I confused you two. I apologize, to both of you. Even if you are an edudonkey.

 

2010 yukon. It hasn't always been this way. Used to not have a problem filling it.

What code numbers?

Look at this -

 

Being an educator, I find it funny to be called an edudonkey. Something I havent been called before but the reference has been made lol. There are a lot of good educators on this forum and not too much we aren't able to solve. I do know the difference between evaporative emissions and exhaust emissions. I only mentioned the tune-up stuff because many people go looking for something that isn't there, only to find they should have stuck to basics.
If you are getting a P0455, I would check the hose from the tank to the intake manifold for rub through or cracking. Common issue on yukons

 

Being an educator, I find it funny to be called an edudonkey. Something I havent been called before but the reference has been made lol. There are a lot of good educators on this forum and not too much we aren't able to solve. I do know the difference between evaporative emissions and exhaust emissions. I only mentioned the tune-up stuff because many people go looking for something that isn't there, only to find they should have stuck to basics.
If you are getting a P0455, I would check the hose from the tank to the imtake manifold for rub through or cracking. Common issue on yukons

Thanks. BTW I wasn't calling you edudonkey.

 

If you are getting a P0455, I would check the hose from the tank to the intake manifold for rub through or cracking.

But that code and it's problems "should" solve his fuel filling problem, which is what I thought was the main problem. That it keeps shutting down the nozzle when refueling.

One thing that many GM vehicles do is they shut down the vent when running, so refueling leaving the engine running gives no venting to the tank. https://www.gm-trucks.com/forums/topic/100571-diffiulty-with-filling-gas-tank-on-yukon/

 

I have a problem with my EVAP system that keeps generating P0442/P0455. I plan to fix this when I can afford to, but in the mean time I've been connecting my scanner and deleting the code every time the check engine light comes on. Is that bad practice? Obviously best practice is to fix the problem, and I am, but is there a finite number of times you can delete these codes before you cause more problems? What kind of storage technology is the ECU using for this? ROM? RAM?

what is your make, model, and engine. how about we help you fix your car.

 

@KeepItSimpleStupid
I'm not to sure about unhooking the battery to clear any codes, If that works its going to be pretty rare cases.
I do spend a lot of time in the hex data of automotive modules tho, can't say I have ever seen the write locations for dtc's or other constantly changing data (like mileage) ever switch around. More likely that if it was not able to write then your going to start getting control module failure codes instead. Also, the speedometer has nothing to do with the dtc's in other modules only its own codes. EVAP will be in the engine control module.

Have you ever heard of Unified Diagnostic Services? Its hard to get indepth info about it. Supposedly its the programming suite associated with modes $01-$09, reflahsing, and other functions in all CAN OBD2 vehicles.

 

Have you ever heard of Unified Diagnostic Services?

No sorry, I don't dig too deep into understanding how the UDS protocol itself works if that is what your asking.

 

No sorry, I don't dig too deep into understanding how the UDS protocol itself works if that is what your asking.

Not trying to hijack this
Ive been interested in the subject for while. Seems to have a shroud of mystery surrounding it in the repair world.

 

This protocol has been around for a while now but mostly used at the developer levels. I have followed VECTOR for about 15 years as they are a major player in this industry but I have never seen a scan tool with UDS protocol in the open market. I have seen it in action though and it does provide a ton of information more than normal Scan Tool technology. The one I saw had about 4X the information that our dealer unit had. Quite impressive. I think you will find these at the engineering level but not sure how you would get your hands on it.
On another note, @strantor, how are you making out with your issue.