CEL P0456 EVAP System Leak, Very Small Leak
11-14-2015, 07:47 PM
#1
Racer
Thread Starter
CEL P0456 EVAP System Leak, Very Small Leak
I have a 2008 C2S Cab with about 32,000 miles on it. My check engine light (CEL) came on at start-up about three months ago. Even though the car continues to run fine, I took it to my independent service center and they ran diagnostics with the following results: P0456 Evaporative System Leak, Very Small Leak, Not Present (it must have been reset by them, 2 occurrences.
The shop ran a smoke pressure test on the EVAP system and were unable to see anything. But based on their experience with other similar cars, they thought it might be the tank vent valve, so they changed that out and reset the code.
I drove the car for the next several days with all systems working normally. Then less than a week later, the CEL came back on, again at start-up. The shop told me to continue to drive the car for a while to see if the light would go out on its own. In fact, after about 2-3 days the light *did* go out (i.e., did not come on at start-up) and stayed out for about 3-4 days. Then the CEL came back on again at start-up. On the advice of the shop, I have continued to drive the car since, and the CEL has stayed on most of the time, occasionally going out for 1-2 days (roughly 5-6 start-ups) here and there.
Given this information, my shop has recommended changing out the carbon canister, and even they are not highly confident this is the problem. It seems to me if we are going to guess, starting with the least expensive possibilities would be a better approach. Also, I have never heard of a relatively static carbon canister failing. I would expect a moving part to be more likely, say a solenoid that is worn and does not close quite properly every time. Also, based on the inconclusive smoke pressure test, I would expect the failure to be somewhat internal, hence hidden.
I recognize that a "very small leak" could be very hard to find, and that it would be easier to locate over time if it gets worse. But I would like to see what, if anything, can be done to locate it sooner so it can be repaired more quickly. I am concerned that driving with the CEL on all the time might mask an even more serious fault. I know my shop has the same concerns.
What's my next move?
The shop ran a smoke pressure test on the EVAP system and were unable to see anything. But based on their experience with other similar cars, they thought it might be the tank vent valve, so they changed that out and reset the code.
I drove the car for the next several days with all systems working normally. Then less than a week later, the CEL came back on, again at start-up. The shop told me to continue to drive the car for a while to see if the light would go out on its own. In fact, after about 2-3 days the light *did* go out (i.e., did not come on at start-up) and stayed out for about 3-4 days. Then the CEL came back on again at start-up. On the advice of the shop, I have continued to drive the car since, and the CEL has stayed on most of the time, occasionally going out for 1-2 days (roughly 5-6 start-ups) here and there.
Given this information, my shop has recommended changing out the carbon canister, and even they are not highly confident this is the problem. It seems to me if we are going to guess, starting with the least expensive possibilities would be a better approach. Also, I have never heard of a relatively static carbon canister failing. I would expect a moving part to be more likely, say a solenoid that is worn and does not close quite properly every time. Also, based on the inconclusive smoke pressure test, I would expect the failure to be somewhat internal, hence hidden.
I recognize that a "very small leak" could be very hard to find, and that it would be easier to locate over time if it gets worse. But I would like to see what, if anything, can be done to locate it sooner so it can be repaired more quickly. I am concerned that driving with the CEL on all the time might mask an even more serious fault. I know my shop has the same concerns.
What's my next move?
11-15-2015, 09:59 AM
#2
Nordschleife Master
The computer has the capability to differentiate between a small leak and a large leak. The computer sees as a large leak the fuel cap,the vent solenoid stuck open or the purge valve stuck open.
Do not change any more parts. Your shop sucks,sorry to say. They are parts changers.
First step : go to another shop. Do your research for a good Independent in your area that is familiar with these cars.
If I were a betting man,I'd say a small leak like that is related to a very small crack in one of the hoses that is part of the EVAP system. The smoke machine is your best friend. I know you said your shop smoked the EVAP system,but I say they haven't done a proper job.
Don't forget : DIAGNOSTIC before swapping parts,never swap parts in the hopes that one will eventually fix the problem.
Good luck!
Do not change any more parts. Your shop sucks,sorry to say. They are parts changers.
First step : go to another shop. Do your research for a good Independent in your area that is familiar with these cars.
If I were a betting man,I'd say a small leak like that is related to a very small crack in one of the hoses that is part of the EVAP system. The smoke machine is your best friend. I know you said your shop smoked the EVAP system,but I say they haven't done a proper job.
Don't forget : DIAGNOSTIC before swapping parts,never swap parts in the hopes that one will eventually fix the problem.
Good luck!
11-15-2015, 10:19 AM
#3
Intermediate
Eventhough it's not the same code as you, I thought it might be useful to share my situation since it's an equally frustrating issue.
I bought a 2009 C2 in August and after about two weeks, I started getting the 5504 Tank System Leak CEL about every 10 days.
After replacing the gas tank cap with no change, I took it to my indy and he ran the smoke test and checked the valve but didn't find any leaks. He told me that he wouldn't want to start changing bits without being sure of what the problem and if it happens more often that maybe it'll be easier to locate the problem. So, we left to that.
In the meantime, I got myself a durametric so I can scan and reset the code myself (drove me nuts to go around with a CEL on) .
I also noticed that if I open the gas tank cap once a week (with the engine off obviously and not necessarily to fill up since I don't drive the car everyday) the CEL does not come back.
Insight? ideas?
I bought a 2009 C2 in August and after about two weeks, I started getting the 5504 Tank System Leak CEL about every 10 days.
After replacing the gas tank cap with no change, I took it to my indy and he ran the smoke test and checked the valve but didn't find any leaks. He told me that he wouldn't want to start changing bits without being sure of what the problem and if it happens more often that maybe it'll be easier to locate the problem. So, we left to that.
In the meantime, I got myself a durametric so I can scan and reset the code myself (drove me nuts to go around with a CEL on) .
I also noticed that if I open the gas tank cap once a week (with the engine off obviously and not necessarily to fill up since I don't drive the car everyday) the CEL does not come back.
Insight? ideas?
01-03-2016, 06:41 PM
#4
Racer
Thread Starter
New clue: The CEL was on most of the time until the temperature dropped below 40 degrees F, but has been off since (several weeks so far). It must be something significantly affected by thermal expansion/contraction.
01-04-2016, 04:32 PM
#5
Burning Brakes
I have this code coming on intermittently as well.
Check your gas cap O ring seal. Mine has several large cracks that point to that seal being the culprit.
It's a $20 part on Amazon and is a 30 second repair. I'm ordering mine right now, actually.
Check your gas cap O ring seal. Mine has several large cracks that point to that seal being the culprit.
It's a $20 part on Amazon and is a 30 second repair. I'm ordering mine right now, actually.
01-04-2016, 07:34 PM
#6
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I just did the same thing. I cleared the code so we will see if it really is the gas cap. My rubber was cracked and I had the code come on 7 months apart. Each time the tank was less 1/4 full. Maybe more fumes in it?
05-14-2017, 11:32 AM
#7
Exact Problem on My 2012 911 GTS
Did you ever resolve your problem? I have changed the gas cap and leak detection module. It is now longer between the CEL coming on. I'm thinking that when the CEL code is cleared the computer monitoring must go through its Drive Cycle before it will actually throw the code again.
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05-14-2017, 01:57 PM
#8
Intermediate
Mine was a 5504 Tank System Leak CEL that was caused by a cracked carbon canister at its base (that an incompetent tech cracked when removing a boomerang tracking module previously - I saw him yanking on a cable with all his strength). It was diagnosed though a smoke test.
Hope this helps!
Hope this helps!
09-23-2022, 10:41 AM
#11
yes