jammaljc

2009 997.1 TT, Durametric gives me this fault code: C1604 Evaporative Emissions (very small leak). Could not find anywhere on the site (or web for that matter) that talks definitively about what this code means, but I am thinking it is the charcoal canister. Hate taking it to the dealer, but I would guess this is probably covered under the factory emissions warranty.

Thoughts?

jhbrennan

Is the fault throwing a CEL? Could it be a one-time event like gas cap loose? If it is an issue I would agree that it should be covered under emissions warranty just not sure how dealer would find without a CEL other than by hooking up PIWIS. Let us know what you find out.

jammaljc

Yes it is throwing a CEL. I have reset it a few times and it eventually comes back, sometimes more quickly than others (at next start, versus days later). I think it more prone to happen when the car has been driven and gets pretty hot, then is left to cool down overnight. I am guessing there is a pressure sensor sensing too much of a drop in pressure somewhere in the system.

aa909

my buddy just had this error. Dealer said it's a faulty cat. do you have sn aftermarket exhaust?

jammaljc

No aftermarket exhaust, it's stock. "Evaporative" and exhaust don't seem to go together to me, though.

Has anyone replaced their own charcoal canister? Is it the same as the 997 non-turbo?

TT Surgeon

I had that, it was my gas cap.

jammaljc

My gas cap seems fine. Did yours seem ok but was still letting pressure leak?

TT Surgeon

Yes, mine seemed fine, but kept throwing the CEL, then put on a new cap, never had another problem.

neanicu

FWIW,the gas cap is a Gross leak,not a Small one.
The canister doesn't leak. The Purge Valve solenoid or the Vent valve(found in the canister vicinity) can be sticking or be stuck open creating a leak. But again,the computer sees that as a Gross leak,not small. There's a chance one of the hoses found in the EVAP system is cracked creating a leak. The only way you'll find that is by smoke testing the system. I suggest you let the dealer take care of it,especially if the car is under warranty.

Tots

First of all, it is good to be here to share info with you guys and pick up knowledge as well. This is my first reply to a thread and first post. It's good to be here.

I have a 2007 997.1T and the first code I came across was a p0456 ( Evaporative System, very small leak) via an OBDII reader. My first thoughts of course was to search the web for answers. Through much looking I came across very little info on the 997T online through different forums. Mostly leading to gas cap issues, carbon canister, purge valves or vent valves and use of the smoke testing to find the leak. All excellent info. With what I know now from solving the problem on my car I hope to help out a little for some one out there on the same boat I was.

The first thing I checked was the simplest thing to check. The gas cap. Visual inspection on my gas cap showed some very small cracks. I replaced it and the light came back on with the same code a couple of days later.

The second thing i was going to try was the carbon canister but after one other post about a 996T spending a butt load of money just to find out the light came back on I decided not to go that route because it was the most expensive route and based on the location of the canister, I figured that unless your car has been in a previous accident that the carbon canister would be one of the least likely things to crack. I placed that on my last ditch effort to change.

The Third thing was to check the change over valve. Not having any kind of experience of where this part would be located. I searched through forums and the best advice I found was someone had mentioned that the valve was by the throttle body. I needed some sort of visual, but found none. So I went to an online parts catalog to try and find the part. After a little hustle I found it.

Image 1

its #22 on the picture ( part # 99660516500)

OR # 4 below (part # 99660516500)


Image 2


On purchasing the parts online and much anticipation I checked the valve as mentioned on http://www.renntech.org/forums/topic...l-p0410-p1411/ ( NOTE ITS NOT THE EXACT VEHICLE ON THAT LINK BUT IT REALLY HELPS GIVE YOU AN IDEA) and the valve on my car was perfectly fine. The part is located behind the throttle body and intake distributor pipe as displayed on image 2. To test it simply look at the valve and it has imprinted (+) and (-) where the connector is on the valve and it runs on 12V. Without current one side should remain blocked and the other two sides should be free when you blow on it. With current it opens up flow and all three sides flow freely. Since mine was okay and I had the new part already. I changed it anyway.

The next thing I tried was the culprit. I checked the vent line (valve). (Part # 99711002973) its # 15 on image #3 below. When the line was removed it pushed air by mouth on one end and had a bit of a passive leak and I could blow on both sides and the leak was there.
I did the same current test and the valve was turning on and off but didn't completely close off without current ( Note that this valve didn't specify with (+) or (-) symbols like the other one ) Since I had a new part I tested the old with 12 volts and opened and closed but it didn't close all the way. I checked the new one by mouth pressure and it was closed and no air passed through. I replaced the part and I havent had it show a leak. Had I tested the part with a smoke machine with the system closed I think it would have stalled me looking all over the place. I got lucky and found the part going the cheapest to more expensive route. But this part by far was the easiest to replace. So, I suggest you check this one first!

Image #3

Tots

I recently ran into the same problem and after much searching and digging on the web and using deductive reasoning I came up with the solution for my 997t - Evap leak - very small leak. I wrote an in depth response about 4 days ago but for whatever reason the post didn't go through. So I'll give you the short version and if you'd like more detail on how I came about it, you can shoot me a PM and I can help out.

I wanted to go the cheapest route first and move to the more expensive parts later. I did it without the Durametric and I'm kind of glad I didn't because I think it would have come out inconclusive because the culprit was still working electronically. So after all the work I did I'll tell you what I feel is the easiest way to go at it from a cost perspective and easiest to go.

I first tried the cheapest and easiest way to start. The gas cap. I noticed some very small cracks on the gasket and I figured why not. It was cheap and worth the try and it was about to give up anyway. But the light came back.

The next thing I tried was the part #9A160516500 EGR vacuum solenoid. It was the next cheapest part. Mine was working fine. No leaks via current testing. It's located behind the throttle body and attaches to the intake air distributor pipe/plenum.

The last one I checked was the culprit. Part #99711002973 VENT LINE. If knew back then what I know now, I would have tested this one first because it would have been the second easiest part to check. You don't even need tools to check if it's leaking. It uses pinch and pull connectors and it is in the engine bay on the left side ( driver side on Left hand drive vehicles) Google the part # to get the visual of how the part looks like in the engine compartment.

Lastly I would check the carbon canister area. To me, it's the least likely to go out or crack unless you have been in a collision. Lucky me I didn't have to go that route.

From this experience I learned that the best tool was the parts catalogue. It gave me true location of the part and part numbers and with a little common sense you can even figure out all the tools you need to do the job right the first time.

Hope this helps! I had a much more detailed version of this post with pictures and links but it didn't post.

jammaljc

Thanks for taking the time to post this. I replaced my gas cap and did not get another "small leak", but I have had a few "large leaks" since then. Only a few, and none lately. I am thinking it could be heat-related (stop and go commute home in 100+ degree Austin weather), and maybe only on a just-filled tank. If I see this again, I'll ask the dealer to start with vent line! I do have warranty coverage. Just really despise taking it to the dealer here.

saabin

Reviving an old thread..

I get this code when I scan with a Durametric (C1604) or OBD scanner (P0456) HOWEVER, it does not trigger a CEL.

I plan to use your excellent writeup here, but was curious about the R&R of the parts.. Did you lower the engine a little to get at the part(s), expecially the one behind the throttle body?

I cant see how you could do this without lowering it some as there is no room to work back there?

Tots

First, If no CEL shown on the dash. Just clear the codes and see if the code comes back. You may not have to fix anything yet. It may have been just a valve that stuck open for whatever reason and now is functioning again. Change it when it doesn't want to go away.

If it comes back, then:

No, engine was not lowered. It's not easy to get to. You have to remove air box, intake tube, throttle body and just loosen the "T" Intake distribution tube in the back enough to turn it to see the back side of it. Invest in some long needle nose pliers ( straight and with a slight angle). Getting those hoses off will be the most difficult part. And make sure you don't grip too hard to where you damage the hoses or you'll be buying new hoses as well.

saabin

Ok, thanks for the info..

I had the code once before, about 3 months ago, and I cleared it then.

I'll start with the gas cap and go from there..

Thanks for the tips!