P0496 – Evaporative emission (EVAP) system -high purge flow
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Last Updated 2016-09-06
ASE Master Tech
| Trouble Code | Fault Location | Probable Cause |
|---|---|---|
| P0496 | Evaporative emission (EVAP) system -high purge flow | Wiring, EVAP valve, mechanical fault |
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What Does Code P0496 Mean?
The volatility of gasoline has both its pros and cons. Liquid gasoline cannot burn, but the ease at which it evaporates makes it’s vapors useful in gasoline-powered internal combustion engines around the world. On the other hand, since gasoline boils as low as 95 F, and evaporates at even lower temperatures, basically until it freezes, at some -50 F, depending on the exact blend. Because gasoline is composed of a number of compounds harmful to plant and animal life, not to mention the environment, gasoline containers needs to be sealed to prevent vapors from escaping.
The problem is that a perfectly sealed gasoline container, such as the gas tank in your car, wouldn’t work very well. Depending on construction, the fuel pump could eventually deform, collapse, or break a sealed gas tank. Refueling would be difficult as well, because air in the tank would have a difficult time escaping at the same time as new gas is being introduced via the fuel filler tube.
To prevent the aforementioned problems, the evaporative emissions control system, typically referred to as the EVAP system, keeps these things under control. Using a system of valves and an activated-charcoal canister, the EVAP system allows for air to enter, as fuel is being pumped out, as well as for air to exit, as fuel is being pumped in. During refueling, the charcoal canister captures any vapors in the escaping air. Then, while the engine is running, the purge valve allows the engine to burn off any vapors caught in the canister. This way, harmful vaporized hydrocarbons and other chemicals are safely burned, the only result being water and carbon dioxide.
As with all systems, the EVAP system, controlled by the ECM (engine control module), includes a number of self-checks to make sure that it is indeed performing properly, reducing evaporative emissions from making it to the atmosphere. In case of a fault, the ECM will set an evaporative emissions diagnostic trouble code (DTC) and illuminate the MIL (malfunction indicator lamp). One common problem in the EVAP system occurs when the ECM detects a vacuum when there shouldn’t be one, for example, if the purge valve is stuck open. In this case, DTC P0496 – EVAP System High Purge Flow will be set in system memory.
What are the common causes of code P0496 ?
Depending on year, make, and model, DTC P0496 may have number of causes. Here are some of the most common.
- 1995-2003 Nissan – Certain Nissan vehicles were prone to charcoal canister leaks, which would cause any number of EVAP system DTCs to set. Tiny charcoal particles could get stuck in the Purge Valve, leading the system to erroneously indicate purge problems and leak problems. Solution: Replace the charcoal canister, blow out the purge lines and vacuum lines, clean or replace Purge Valve and other EVAP system valves. (Caution: Do not blow out purge lines or vacuum lines with shop air unless you are sure they are completely disconnected. High pressure can easily ruin other parts of the EVAP system.)
- Carbon Deposits – Some automakers put the Purge Valve directly on the intake manifold, which can lead to heating and the accumulation of carbon deposits. If enough carbon builds up, it could hold the valve open. Cleaning may or may not be sufficient to restore proper sealing.
- Poor Installation or Repair – Least common is a short-to-power condition, which may be caused by poor installation of an aftermarket accessory or mis-routing of the harness following a repair.
What are the symptoms of code P0496 ?
Depending on how your vehicle is designed, you may or may not notice any drivability problems concurrent with an EVAP DTC. At the very least, you will experience diminished fuel economy, as the ECM may be running in “limp-home” mode. Concurrent EVAP system DTCs may also be present.
On the other hand, you may notice drivability problems, such as low power, poor acceleration, even misfiring, due to unmetered air entering via the EVAP system. Concurrent DTCs may include System Rich or Lean codes or Cylinder Misfire codes.
How do you troubleshoot code P0496 ?
Determining the cause of excessive purge flow should be relatively straightforward. Since the ECM has determined that there is vacuum in the system when not commanding EVAP Purge, the problem has to do with the purge valve itself or the circuit controlling the purge valve. A wiring diagram from All Data DIY for your vehicle will be helpful.
- Purge Valve Check – The easiest way to check for a stuck-open purge valve is to disconnect the EVAP hose while the engine is running. There may be more than one line connected to the purge valve, depending on if the valve is connected directly to the intake manifold or not. One line should always have vacuum when the engine is running. The other side, which connects the purge valve to the charcoal canister, should only have vacuum when the ECM commands it.
- Start the engine, then disconnect the EVAP hose. If the valve is stuck open, you may be able to hear air sucking into the open port, or you should be able to feel the suction with your fingertip. The engine may start to run erratically, as well, due to the large vacuum leak you just created.
- If you have a hard time detecting any leak with your ears or fingers, connect a vacuum tester to the open port. Unless the ECM commands it, the Purge Valve should be closed, which means you should measure no vacuum at the open port.
- If you feel or measure vacuum at the opened port of the Purge Valve (most ECMs block purge flow at idle) disconnect the Purge Valve electrical connector.
- If the vacuum doesn’t drop, then the problem is in the valve itself, stuck open because of corrosion or contamination. Clean or replace the Purge Valve. Because the Purge Valve is so “inexpensive,” some suggest simply replacing it as a matter of course, but we suggest doing a full diagnosis before condemning it.
- Pro Tip: Inspect the purge line, as well. In case you find flakes of charcoal, this could mean the charcoal canister has leaked or is leaking, and will need to be replaced. If you do not replace a leaking canister and blow out all the purge and vacuum lines, you may end up with EVAP system DTCs again in a very short time.
- If the vacuum drops to zero when you disconnect it, then the problem is likely a short to power in the wire harness, which isn’t impossible, but not a common occurrence. Use a DVOM (digital volt-ohm meter) to determine where the short to power is in the harness between the ECM and the Purge Valve.
Codes Related to P0496
The following are a number of EVAP system codes, which may or may not be found concurrently with DTC P0496:
- DTC P0440 – Evaporative Emission Control System Fault
- DTC P0441 – Evaporative Emission Control System Incorrect Purge Flow
- DTC P0442 – EVAP Emission Control System Leak Detected (small leak)
- DTC P0443 – EVAP Emission Control System Purge Control Valve Circuit
- DTC P0444 – EVAP Purge Control Valve Circuit Open
- DTC P0445 – EVAP Purge Control Valve Circuit Shorted
- DTC P0446 – Evaporative Emission Control System Vent Control Circuit
- DTC P0447 – EVAP Emission Control System Vent Control Circuit Open
- DTC P0448 – EVAP Emission Control System Vent Control Circuit Shorted
- DTC P0449 – EVAP Emission Control System Vent Valve/Solenoid Circuit
- DTC P0450 – Evaporative Emission Control System Pressure Sensor
- DTC P0451 – EVAP Emission Control System Pressure Sensor
- DTC P0452 – EVAP Emission Control System Pressure Sensor Low Input
- DTC P0453 – EVAP Emission Control System Pressure Sensor High input
- DTC P0454 – EVAP Emission Control System Pressure Sensor Intermittent
- DTC P0455 – EVAP Emission Control System Leak Detected (gross leak)
- DTC P0456 – EVAP Emission Control System Leak Detected (small leak)
- DTC P0457 – EVAP Emission Control System Leak Detected (fuel cap)
- DTC P0497 – EVAP Emission Low Purge Flow
- DTC P0498 – EVAP Emission Vent Valve Control Circuit Low
- DTC P0499 – EVAP Emission Vent Valve Control Circuit High
Other non-EVAP system codes may include:
- DTC P0170 Fuel Trim (Bank 1)
- DTC P0171 System too Lean (Bank 1)
- DTC P0172 System too Rich (Bank 1)
- DTC P0173 Fuel Trim Malfunction (Bank 2)
- DTC P0174 System too Lean (Bank 2)
- DTC P0175 System too Rich (Bank 2)
BAT Team Discussions for P0496
- 2004 grand prix P0496
2004 grand prix P0496 with a 3.8 L just need to know what this code is and if a possible flow chart available. Thanks... - 08' Chevy Avalanche check engine light on with decreased gas milage
More detailed information... DTC P1174 or P1175 Diagnostic Instructions - Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. - Review Strategy Based Diagnosis for an overview of the diagnostic approach. - Diagnostic Procedure Instructions provides an ... - 0496
what vehicle- year. make, model, eng, trans, color? This is a P0496? that alpha character is needed when discussing codes. . What is - purge value, evap VP? Purge is on or off - maybe knowing vehicle will help explain-...
I have the p0496 code but the light is not on on the dash and what would be the estimate to have this fixed does anyone know thank you in advance
Richard-
Please give us some vehicle information to help you out. Year, Make, Model, Engine, any recent repairs?
Given that the MIL is not on (Does it actually work? KOEO, the MIL should light up as a self-check.), it’s quite possible that this is a history code, and your vehicle isn’t currently experiencing any faults. Clear the code and keep driving.
-Ben
I have a chevy uplander it’s a 2007 the light came on on the dash and I got it looked at and they told me that it’s a P0496 Evaporative emission system high purge flow what dobi get to fix my van
Oh and I’ve already replaced the gas cap, but the check engine light came back on.
2006 STS Cady I replace the canister purge valve now my engine light came bsck
Peter-
Did you make sure the canister purge valve is working and connected properly? Bench test the new valve and make sure the connector and hoses are properly seated. Also, make sure you are using a good factory gas cap. Faulty or aftermarket gas caps may not seal or vent properly for your vehicle. Is the canister in good condition? At ten years of age, you may have corrosion and sticking in the vent valve, which would cause problems with purging.
-Ben
I have a code p0441 and my fob not working my radio or interior lights i check fuses they look fine i have door open light on dash and check engine light now just came on HELP ME PLEASE any one know what i should do i have a Mazda3 2007
Jenny-
First, start with checking the gas cap and the purge valve. At this age, it’s quite possible that the canister close valve is causing problems, corrosion and sticking specifically.
The other problems could be any number of things, which unfortunately I wouldn’t be able to address via internet connection! =)
-Ben
I have a 2006 Kia Rio. During this year alone, I have had all spark plugs and coils (also tires) replaced as well as the battery. I went in for an engine light testing at a local autozone, which came back as “error” three times. I went to an O’Reilly and after two times with an error and waiting about 10 minutes for the third, the P0496 code came up.
He wasnt much help when it came to telling me what that code meant. I have zero knowledge about cars and although Ive read this article many times over, I still dont understand what is wrong with my car.
Alina-
Evaporative emissions are basically gasoline fumes. The EVAP system saves them in the charcoal canister at the rear of the vehicle, by the fuel tank. Tubing connects the fuel tank, canister, and engine. The canister purge valve is the one that allows the engine to suck in fuel vapors to be burned.
I believe the purge valve is located by the throttle body, on the intake. It’s a simple valve connected to two hoses. One of those hoses goes to the engine, and the other comes from the charcoal canister. Disconnect the electrical connector and remove the hose going to the charcoal canister, the one going “down” from your perspective looking at it, and then start the engine. Put your finger on the open end of the valve. If the valve is bad, you’ll feel the engine sucking on your finger. (This is the most common problem, when the valve goes bad, sticking open and allowing the engine to suck on the EVAP system all the time.)
-Ben
I have chevy suburban 07 i put a rebuilt engine still having problems engine light and i increase speed at65 and up it makes humming noise when i let go the gas peddal i dont hear that noise but still vibrating.the people put the engine it saying nothi ng wrong with engine. The code on engine light show P0496 EVAP
Thank you
Tanya-
It seems to me that the EVAP code may just be a coincidence, because you probably wouldn’t notice anything wrong with the vehicle with high purge flow at 65 mph, which is when the EVAP system is most active. On the other hand, if you noticed stumbling or had a system lean code at idle, when EVAP should be shut off, I would suspect a stuck-open EVAP purge valve.
I’m not sure if the hum and vibration are related, however.
-Ben
one code coming p0469 evap system . vechical chevertal travers
Muzahid-
Check for vacuum at the purge valve when the engine is idling. At this point the purge valve should be closed. You can disconnect it to make sure. If there’s still vacuum, replace the valve. Only be sure to check for charcoal in the tube, because that might get stuck in any new valve you install and end up with the check engine light on again.
-Ben
I have a 09 traverse with same issue. Were you able to resolve the isssue and how?
Hi. I have a 2004 buick rendezvous. It is coming up with the evaporative emissions system high purge flow code. If I replace the valve you are discussing will that be it or could there be some other reason for this code.
Mary-
That is the most-common issue, but make sure there is no evidence of canister leakage, because that might clog up a new valve and you’ll be right back where you started.
-Ben
I have a 2009 Hyundai Accent GLS. I was recently getting cylinder misfire codes for 3 out of 4 cylinders! I went ahead and got all spark plugs and ignition coils replaced, but now I’m getting the P0496 code too… Do you think a bad purge valve could have been the source of the misfires? Should I go ahead and replace it too?
Thanks!
Gabe-
Are you saying you still have misfires? I would try disconnecting and plugging the purge line at the intake to verify this. If the engine runs smooth with the purge line plugged, then you have a major vacuum leak through the EVAP system.
-Ben
I got a caddy cts 2005, and changed purge solenoid, canister, purge valve, and starting to feel hopeless because the check engine light persists and same high purge flow is showing, maybe they didnt put the one above the tank right not sure, ive dealt with shady mechanics. And dont knoe what to do?
Eric-
I understand your concern. Of all the systems on the vehicle, I’ve always found the EVAP system is the most difficult to diagnose and repair.
Fortunately, checking the purge valve is easy. With the engine running, disconnect the purge valve connector and remove the EVAP line from the purge valve on the side opposite the intake. The idea is to verify that the purge valve is sealing properly, because the purge valve should be closed unless the ECM commands it to open. If you can feel engine vacuum with your fingertip on the purge valve inlet port, this means the purge valve is stuck open.
-Ben
Hi, I have a 2009 Buick Enclave with 170000 miles on it and a crate motor replaced approximately 40 K ago. I had the oil changed at a lube change place last week. They changed out the air filter and now I noticed the check engine light is on. I have an OBD tool and the code is P0496. I quickly checked under the hood and didn’t see any thing obvious. Is it possible that they may have unplugged something in the process of changing the air filter as it seemed that they had a struggle with it.
Don-
Definitely check around the air intake for any loose or disconnected hoses. Barring that, it may be simply coincidence that P0496 is showing up now.
-Ben
I dug a little deeper checking the valve. During idle there is vacuum with the hose disconnected. When I pulled the electrical connector off the valve the vacuum went away. Obviously something is telling the purge solenoid to energize. One wire of the connector goes to a common 12v source shared with a lot of other stuff so I don’t believe the problem would be on that side but the other wire goes to the ECM. So before I start blaming the ECM what input to the ECM would tell it to energize the purge solenoid. Is there possibly some obscure sensor located somewhere that could cause this?
Don-
Is it possible that there’s a short to ground somewhere between the purge valve and the ECM?
-Ben
my 2012 avalanche has p0496 code and when I fill up doesn’t want to start, starter keeps running. your info is very helpful what else can you add. haven’t tried remedy yet
Matt-
This appears to be a common problem on that vehicle, and it may be related to overfilling the tank, though I can’t be sure in your case, but you said refueling so it made me think about that. The purge valve sticking open is a common issue, but it could be caused by a failed canister. I think I would start with checking the purge valve to see if it is closed when its disconnected. If the purge valve is stuck open, it could cause starting problems, but I don’t know why it would do it only when you fill the tank. EVAP problems are a pain…
Here’s a great thread on ChevyAvalancheClub that explains the correlation: http://chevyavalancheclub.com/index.php?topic=21301.0
Start with checking the purge valve and get back to us.
-Ben
Thanks Benjamin it was a stuck vlv only took 10 min.to change and the code cleared runnin like a top. Matt
Matt-
That’s great!
-Ben
I have a 2013 chevy sonic had to buy a gas cap resently and got my light reset and it has come back on after three days of being off with this code p0496
Monica-
The three days thing is pretty typical, though, because the car can’t run the EVAP test unless conditions are just right, including fuel level, fuel temperature, ambient temperature, cooldown time, etc.
Did you get the gas cap from Chevrolet? Some aftermarket gas caps don’t play well with EVAP systems.
-Ben
I am having a hard time finding where my purge valve is exactly on my 2015 chevy camaro. Can you provide a diagram?
Tori-
I hope this helps. It’s a diagram pointing out the purge hose under the intake cover, but I’ve highlighted the purge valve in yellow.
-Ben
Thanks helpful!!
Hi I have code po496 on my 2010 Chevy suburban 1500 any help thanks
Hi, I am getting a code P0495 on a 2011 Chevy Cruze 1.8L, I picked up a new Valve and replaced it, it still has a clicking sound when I run the car, and it didn’t clear the Check Engine Light. I have driven about 15 miles since changing it. Can it take longer? Is the clicking normal? Or could it have been a faulty replacement?
Hi Benjamin,
I have a 2007 Kia Rio5 and had the P0496 code pop up as well as a cylinder 1 misfire. I noticed the car started misfiring in the morning on cold start which lead me to believe that my purge control valve was faulty. It would also smell of gas but when id look for the leak, I could never find one.
I replaced the valve and both issues went away for 2 weeks. This morning it happened again and had the same codes which is frustrating to say the very least. I replaced the old valve with an OEM valve. Any suggestions? Thanks!
P.S. I should add that prior to.changing the valve, I also replaced the spark plug and coil pack.
Orvais-
Apologies for the delay. EVAP codes could indeed return after a couple weeks, depending on how often you refuel. Depending on the vehicle, the EVAP system monitor may only run when certain conditions are met, such as fuel level, engine run time, ambient temperature, etc. If all those conditions aren’t met, the monitor won’t run and the fault won’t be found, so there won’t be any DTC yet.
I can say that the spark plug and coil pack wouldn’t have anything in themselves to do with the EVAP system, but I have to wonder if perhaps you left something loose when you were replacing them? I would recheck, just to be sure.
-Ben
I have a P0496 on a 2009 Cadillac CTS V-6 diagnostic message. What does this mean in layman’s term? What needs to be removed and replaced? What needs to happened? Thanks.
I have a 2015 chevy traverse and I ran it almost out of gas when I finally found a gas station i put gas in it and when I started it is made a awful noise and was shaking finally it leveled out and the next day my check engine light came on had it checked and its showing code PO496 is that what i should have replaced or try something different the light went off after the machine checked it but has came back on.
Hi. I have a 2011 Chevy treverse. I got the code P0496 also. When I put gas in the car and when I get ready to start it, it feels like it’s going to flood. How long Can I drive it this way before I can get it worked on at the end of the month?
I have a 2010 CTS Cadillac with the check engine light on . Code I received from Advanced auto was P0496. How expensive is this to repair. How urgent is this issue
Hello. I have a 2013 Chevrolet Impala LS with a little over 96k miles. I have codes P0420, P0442 and P0496. Immediately I’m being told to change the catalytic converter. Nothing else has been considered. I’m looking to remedy the possible causes because it is affordable to me before I dish out $800 for one cat to be replaced. Can anyone of those codes trigger the P0420? At one point, there were codes P0590, P0171 and P0174. Those codes disappeared and the other three codes (P04xx) remained. Nothing has been fixed. I have been doing some research. I want to know if I fix the P0496 issue will the other codes go away? Is it possible that’s the only problem? As a backup, I also plan to change the vapor canister as it detected a small leak. I just want to make sure I can pass smog. I need my car. Any help in the right direction would be appreciated.
I have a 2005 chevy cobalt and I’m receiving a p0496 evaporative emission system high purge flow Error on an OB1. What causes this? How can I fix this? Is it easy to do it myself or is it better to take it to a shop?
2015 Chevy Traverse my check engine light is on, and my automatic hatch back door will not open or close using the button or remote, have a P0496 code on diagnostic check
I have a 2013 Buick LaCrosse. I recently replace my gas cap but after a couple days the light came back on. I got the p0496 from pepboys and after I gets gas it stalls to start back up. How do I fix the problem
I have a code of evaporative emissions system high purge flow. Po496. The check engine light came on. Someone told me that it could be from getting gas where they didnt seal the cap tightly. Could this be the cause of code? Yes i am a single mother so i am trying to fix myself.
I have a 2007 chevy equinox lt 6 cylimder 3.4liter
I’m having an issue fixing code P0496. It was told that replacing the Canister Purge Valve should fix this problem, which I did. All was well for the next couple of days and then the code showed back up. I’m unsure on how to proceed.
I have a 2011 GMC Terrain.
Any help on this would be greatly appreciated. The winter months are here and do to the fact that my check engine light is on, the remote start doesn’t work. BUMMER!!!