P0496 – Evaporative emission (EVAP) system -high purge flow
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Last Updated 2016-09-06
ASE Master Tech
| Code | Fault Location | Probable Cause |
|---|---|---|
| P0496 | Evaporative emission (EVAP) system -high purge flow (Buy Part On Amazon) | 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:
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?
Hi Dan,
I have the same issue , 2011 Chevy Traverse3.6
What was the solution on your vehicle?
Don-
Is it possible that there’s a short to ground somewhere between the purge valve and the ECM?
-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 Buick ENCLAVE 2010 I have P0119 and p0496 I already change it do not erase from my scanner Still pops up
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!!!
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 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
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
[…] a leak in any of the associated lines. I've attached an image from the following site for clarity; http://www.troublecodes.net/pcodes/p0496/ Attached […]
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?
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 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
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 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.
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
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?