P0449 EVAP system Vent Control Circuit High trouble code on a 2005 pt cruiser

I have a 2005 PT Cruiser 2.5L Turbo with a P0499 Evaporative Emission System Vent Valve Control Circuit High, I have changed the fuel cap, vent solenoid and the NLVD solenoid. Driven the car 150 miles and still can not get the code to clear. I am in need of help troubleshooting this issue.

John E

This code states that there is a fault in the circuit so you will want to inspect the wiring.

Shorts, opens, and high resistance.

What diagnostic tools do you have? Test light? Bidirectional scan tool controls?

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It doesn't look like this car has a traditional vent valve. I saw a purge valve in the diagram and this leak detection pump that has a solonoid in it, which I'm guessing acts as the vent? Is this one of the parts you replaced?

The diagram shows this being a power side switched circuit. I would imagine there would be no voltage on that circuit until commanded on, then there would be 12v on the wt/dg wire up to the valve and 0v on the black wire after it.



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I have a power probe 3 and volt meter

I think you could disconnect the harness from the LDP to keep the PCM out of the test and apply power to the switch and the solonoid. If they both work, then your problem is between the PMC and the LDP. If one doesn't work, check that power side of the LDP. If neither work, could be bad LDP, but more likely an issue with the ground side.

That's where I'd start, but there may be a more efficient way to eliminate variables. Someone else can throw in some ideas or corrections if needed!


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Tutti57 wrote: I think you could disconnect the harness from the LDP to keep the PCM out of the test and apply power to the switch and the solonoid. If they both work, then your problem is between the PMC and the LDP. If one doesn't work, check that power side of the LDP. If neither work, could be bad LDP, but more likely an issue with the ground side.

That's where I'd start, but there may be a more efficient way to eliminate variables. Someone else can throw in some ideas or corrections if needed!

You're right on about the solenoid! Definitely power side switched. That white/dark green wire should have 12V when the PCM commands the solenoid closed.

That switch is a bit different. It's actually an input, which is provided ~10V from the PCM on the orange/yellow wire. The switch pulls that voltage down when the pressure in the tank goes below 1" water. The switch can operate completely independently of the solenoid. It's goofy! :silly:

If gysgt can confirm that the solenoid is working electrically, then we can check the wiring. With the engine running and the LDP plugged in, what's the voltage readings on all three wires?

Nevermind. I overlooked Tyler's post. He is spot on.

Wells tech Youtube channel has some great Evap videos.
Chrysler Evap

There's a link to the Chrysler Evap video, NVLD starts at 39:30

bruce.oliver wrote: Wells tech Youtube channel has some great Evap videos.
Chrysler Evap

There's a link to the Chrysler Evap video, NVLD starts at 39:30

You're spot on with that video. I dunno that SD has done an NVLD video yet...

Monde wrote: Thanks, Tyler. Just went on all data and realized that the Org/Y wire is a signal(input) to the pcm. I would have seen that if I were paying more attention to the direction of the arrow in the switch.(pointing towards the pcm). My apology!

What arrows are you talking about? Are you talking about the << in the diagram? That is not circuit direction. You only see those at connectors on the diagram. It tells you which side of the connector is male terminals and which is female. So with it this way << the female terminal is to the left and male to the right. This way >> the male terminal is on the left and the female on the right.

How you can tell that that switch applies ground to the PCM is how the switch itself is drawn, it is drawn like any other switch like relays or ignition switches. It is drawn in it's normal state, which is open. Follow the ground from G104 into the NVLD, it puts ground to the switch and the NVLD solenoid. So when it closes it provides a path for the ground into the OR/YL wire.