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Check Engine Trouble Code P0496 How to Diagnose GM EVAP Problems

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Created on: 2021-06-05

In this video, Andy shows you how to diagnose the EVAP system in your vehicle for code P0496.

Here we have a 2012 GMC Acadia with a check engine light on and sometimes a rough idle. Let's check it out. We scan tested the vehicle and the codes that we have are a P0496, which is EVAP system flow during non-purge. So what does that code mean? Let's talk about the EVAP system.

The reason for the EVAP system is to prevent any of the fuel vapors from entering the atmosphere. There is many different components that make up the EVAP system. We'll start from the rear of the vehicle and work our way forward. Let's start with the gas cap. That's gonna be attached to a filler neck that goes to the gas tank. Attached to the gas tank, we're gonna have the vapor canister that goes to a vent.

Somewhere in the back, there should be a pressure sensor whether it's in the fuel tank or in the vent valve. It depends on the vehicle. That's going to read whether the system is working properly. Then you're gonna have lines that go to the front of the engine where the purge valve is. That's what's gonna give the system its vacuum.

If any of these systems are not sealed properly or working properly, you're gonna get a check engine light with an EVAP code. Ours is related to the purge valve so we're gonna go there first. The purge valve on this vehicle is attached to the intake. That's where it's gonna get the vacuum. It's a valve that opens and closes when commanded. And that's gonna apply vacuum to the EVAP system.

This valve is normally in the closed position. And when the computer sends voltage and ground to it, it's gonna open the valve and apply more or less vacuum as needed. For the description of the code, it basically says that that valve is sticking open when it's not commanded. A quick and easy way to test this would be take the valve off, disconnect the connector, and see if you can blow through the valve. Another easy way to do this, take this hose off. Right here, this goes to the rear of the system. Disconnect the connector, and we'll start the vehicle.

While the engine's running, you can check at that port and see if you have vacuum. If you have vacuum, the valve is bad. It's got to be replaced. As you can see, I'm just using my finger and my glove is actually getting sucked into the valve, which means there's vacuum there, the valve is bad. You could also use a gauge and see if you have vacuum there.

We're gonna have to replace that valve in order to fix this check engine light. Luckily, it's right on top. We'll just take a bolt out, slide the old one out, slide the new one in. It should be good to go. If you enjoyed this video or it helped you out, make sure you subscribe to our channel. Ring the bell. Turn on All Notifications so you don't miss any of our videos.


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