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Dodgerench, ASE Certified Technician
Category: Chrysler
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Experience:  30+ years Dodge/ Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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Chrysler Pacifica: I have a 2006 Pacifica FWD throwing codes

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I have a 2006 Pacifica FWD throwing codes P0456, P0441, and P0440. Tried new gas cap and new NVLD pump with no success. What should I do now?

You have a mixture of evaporative system leak, purge performance and general evap system failure codes... the sum of which often means you have a bad NVLD or an extremely large evaporative system leak. Hi, my name isXXXXX to Just Answer!.


NVLD stands for natural vacuum leak detector, which is actually the evaporative system cop. Its job is to partly seal the evap system during testing to allow a slight vacuum to be created in conditions such as an overnight cold soak or while driving and the purge system is active. If the NVLD never detects a switch state change between open and closed as vacuum is expected to build, one of these codes will be set, depending which system is actively being tested at the time. To have all three (especially the P0440 "general failure") code almost always means there is a problem with the NVLD unit or wiring going to it.


I wouldn't expect the NVLD to be completely disconnected or smashed at this point because a P0499 NVLD control circuit code would be present if that were to happen. It's more likely that the NVLD unit has suffered a failure with its internal vacuum switch mechanism or you have a leak large enough to prevent any sort of vacuum accumulation in the evaporative system. A fuel odor will likely be noticed if that's the case.


The most likely place to find an evap leak on these units will be very near the NVLD itself, which is about even with the driver's door handle under the vehicle and shifted toward the same side of the car. NVLD is a 3-wire unit with two large 1/2" diameter hoses connecting to it.


While not expected here, a complete blockage of the vent side of the NVLD unit can produce these same codes. Venting occurs on the large U-shaped hose , ending at a black plastic canister about the size of a can of beans right next to the NVLD. You should be able to blow through the hose from NVLD to the vent and if it flows freely... it's not a venting issue.


Examine the wiring at the NVLD for breakage or pull-out in case they happened to encounter a road hazard of some sort. Once again, the chances of wiring damage without setting a P0499 are slim, but need to be checked.


If you can see no visible damage to any of the lines, NVLD or vapor canister (large black plastic unit with hoses coming out near NVLD), I'd expect the NVLD to be bad. Further testing with the factory scan tool to monitor switch state and the ability to evacuate and smoke test the system for leaks add certainty points to the diagnosis, but I'm doubtful that you have these specialty tools lying around. =/


Replacement of the NVLD requires minimal hand tools, needing only a flat-blade screwdriver to release the plastic mounting tab and maybe to help pry the hoses off. Be careful to avoid splitting or tearing the hoses as that will create the sort of leak that the system is designed to detect.


Once replaced, you can clear your codes manually with a scan tool or by doing a battery disconnect of 30 seconds or more. The next few days will tell the story as to the effectiveness of the repair as the lamp either comes back on or doesn't. Conversely, you can leave the codes intact and drive it the same amount of days, watching to see if the MIL goes OUT as the vehicle tests and accumulates good trips... positive testing that shows no evidence of failure.


Let me know if you have any questions or problems and I'll get back to you as soon as possible. I'm at work today but will keep an eye out for your reply.


Good luck!


Customer: replied 5 years ago.
Yesterday (Friday) I replaced the NVLD and the two vacuum hoses connected to it. The day before (Thursday) I had the codes reset after having them read. The CEL is still off, but yesterday a little while after replacing the NVLD the odometer display started to read "GASCAP." I reset it, but it came back on again.

Dang. The GASCAP prompt in the message center is basically the same thing as a 1-trip failure of the evap system. It still thinks there is a problem.


It's odd that you're only now getting the GASCAP message. Did it ever tell you this before?



Customer: replied 5 years ago.
Last winter. At that time I tried a new gas cap with no luck. The CEL has been on since then, but I think the GASCAP message went away when the CEL came on back then.

That's the way it should work. The GASCAP prompt gives you time to correct a left-loose gas cap before it turns into a full-blown trouble code. All it takes is a couple Good Trips afterward and the warning goes away. The GASCAP warning actually can't be erased directly, needing an OK from the Evap Leak Monitor after it's actually seen these Good Trips even if the problem is fixed.


We might have to do some improv at this point. Testing of the evap system doesn't lend itself to outside-the-dealer circumstances as you can imagine. Do you have a way to lift the vehicle high enough to do electrical testing right at the NVLD? We'll need a digital multimeter as well....

Customer: replied 5 years ago.
I can lift the vehicle and have a multimeter. Lead on...
Actually, let's try something else first. Let's do something like a leak test.

Block the NVLD at the outlet end (you can disconnect the filter and stuff something in it or just use needle-nose locking pliers). Start the engine and let it run about 5 minutes if it was previously cold... less than that if it's already warm.

What you've done is sealed the only vent in the evaporative system by blocking off the NVLD. After a run cycle of only a few minutes, the purge solenoid will begin pulling vapor from the vapor canister which will create a negative pressure in the evaporative system including the fuel tank.

After it runs a little while, crack the gas cap and listen for a pressure exchange. It's hard to tell if it's pressure leaking out or air going in, but if you smell no fuel vapor near the cap... it's pulling in.

If this works (and it should), we've proven that the purge system is operational and that you have at least a partial seal on the evap system.

Once you've seen the wooooosh effect, let the engine run a bit to allow the purge system to evacuate the evap system and then disconnect the purge solenoid electrical connector. The purge solenoid is located almost directly behind the right side headlamp in the engine compartment, has two hoses running to it and a 2-wire connector. It's not easy to get a paw on, but bear with me. The red slide-lock on the connector must be clicked to its opposite position before the release tab will be enabled. Then slide it off and happily set a P0443 trouble code we can erase later.

Now disconnected, the evap system should have a partial vacuum stored. I had you disconnect the purge solenoid because the PCM sometimes cycles the solenoid open at key-off, which will destroy our test.

Let it sit for about a minute, then crack the gas cap again. You should get a decent woooosh once again if vacuum has been retained.

No vacuum... ever? We might need to verify that the purge solenoid is working and that its vacuum hoses are intact back to the intake manifold. It's a step by step process and I'm kind of making this up as we go...

Talk shortly!
Customer: replied 5 years ago.
I won't be able to try this for a couple hours or possibly tomorrow. I will update you then.
That will be fine. I'll be around JA on and off through the day and will watch for your post.

Have a great night!
Customer: replied 5 years ago.
Okay. I clamped the line to the filter, then ran the engine 5 minutes. When I cracked the gas cap, I heard a whoosh and did not smell fumes.

With the clamp still in place, I ran the engine another 5 minutes and disconnected the purge solenoid while it was running.

I shut off the engine, then one minute later cracked the gas cap open. I got the whoosh.

Your move.
Very good. This shows we have at least some sealing of the evap system and certainly have purge flow performance, but this test at least shows that a gross leak isn't present. Gross leaks are one of the reasons a P0440 code can set.

I'd look at the NVLD output switch at this point. For me, it's much easier because I can use the factory scan tool... but you'll have to tap directly into the wire for the same effect. Not quite so handy. =/

Your NVLD has three wires.

The black/ white wire is a straight ground and should test as such, showing less than 10 ohms of resistance between this terminal and body ground or battery negative.

The violet/ white wire (center) is the signal circuit and will toggle between a state close to that of battery voltage as the switch internal to the NVLD closes or opens.

The violet/ light blue wire is the solenoid control circuit that begins at the PCM and ends here. Its job is to electrically control the valving built into the NVLD for venting or sealing.

As I hinted, NVLD has an internally controlled valve for venting or sealing the evap system, depending on circumstances. When the engine is off, the NVLD will remain in its normally-closed (non-vented) position which is how it actively tests the system for leaks.

With the system sealed, the effects of decreasing pressure in a sealed vessel will always result in a reduction of pressure... the old "gas law" you learned about in science class. This is how the system finds small leaks and larger ones when the purge system is active; a reduction in pressure closes the NVLD internal pressure switch.

Tap into the center wire of the NVLD, select 20v DC on your meter and ground the other test lead. Turn the key on and remove your hose clamp.

Monitor voltage on this circuit and then start the engine, allowing it to run long enough to enter the purge phase.

Voltage on this circuit should toggle between high-to-low or low-to-high. Forgive me, but I don't test the circuit this way often and I forget which way the switch circuit works. Anyway, there should be a change of state if the NVLD is doing its job and we don't have leakage in excess of the amount to provoke a switch state change.

The amount of pressure differential needed is tiny. Only 1" of H2O (not Hg) is needed, the same amount of vacuum needed to pull an inch of water up a straw. It does't take much.

Once you see a state change, turn the engine off and then roll the key back on rapidly to monitor switch voltage. It should remain at the same state it was in before turning the engine off and stay in that state for close to a full minute, depending on ambient temperatures.

Ambients have an effect on this test because gasoline is naturally so volatile, tending to evaporate easily which will mess up a perfectly good vacuum. It's later once temperatures drop that the NVLD is actually better at its job, but this is what we're working with for now.

In summary, tap into the signal wire.
Monitor switch state with no vacuum in the system.
Produce vacuum by running the engine a short time.
Once switch state changes, give it an additional 10 seconds and turn the key off.
Turn key back on.
Continue to monitor the switch state for decay.

Customer: replied 5 years ago.
The voltage seems to always be high, around 9-10 volts. I can't get a state change. I have run the engine up to 15 minutes and turned it off and waited up to 15 minutes too. No matter what, I see the same thing.
Ooooooo... we're getting close.

The problem with this... um... test as I described it is that the PCM may have the vent valve open on the NVLD the whole time so it won't build vacuum. I'm pretty confident that your evap system is mostly leak-free at this point and we definitely know that the purge system is operational. And although a lost ground at the NVLD should set a P0499 code, I'm not completely ready to sign off on that one until you can get a continuity test between the black/ white wire and body. It's mostly a formality, but that's how we work... checking things off as we go.

If OK, we need some way to induce an artificial vacuum in the evap system on demand with the key on and engine off. I considered a shop vac, but the vapor being pulled into the vacuum chamber would be potentially explosive and it takes a long time to grow those eyebrows back.

For reasons I can't quite explain, you can't reliably get a switch state change on the NVLD if you clamp off the vent line, even though this is essentially the same thing it does on its own. But I have an idea.

Build system vacuum using the clamp and several minutes of run time. monitor your NVLD signal circuit for change and turn the engine off.

Turn the key back on.

While watching your NVLD switch state, release the clamp. It should vent to about .5" Hg and hold since the normal state of the NVLD is relaxed and sealed. This state is more than sufficient to close the internal switch.

Then compare this switch state to what you see when removing the gas cap. It SHOULD change. You probably won't hear the satisfying wooooosh sound because the pressure exchange will be much less intense, but it should still happen and result in an NVLD switch change.

Check the ground first though... just because.

Enjoying your weekend? =/
Just thinking.
Crawl under your Pacifica again, locate the signal wire and separate it from the harness for a good foot or so.

Pull hard.

I'm thinking it's gonna snap. I'm not seeing an exotic failure here on closer examination... it's a broken wire. Rock strikes can rot a wire from the inside out and even if it appears to be in one piece, a good tug will usually tell the story.

If it breaks with a few pounds of effort, you've got your boy.
Customer: replied 5 years ago.
Oddly enough, I unintentionally broke the signal wire when I was first trying to tap into it. I was peeling back the electrical tape at the time. I figured I was being too rough, so I spliced it and carried on.

Do I replace one wire or a harness?

One wire! This is a really low-load circuit and if you could snap it that easily, something was already wrong there.

Is there enough wire left outside the connector to connect to?
Customer: replied 5 years ago.
Yes, there's a few inches. What's the best way to splice it?
I'm a fan of solder-and-shrink tube in almost every repair, but the most important thing is that you get good connectivity and seal it from the environment. A simple crimp splice will do OK as long as the connections are made to good, shiny copper and then sealed up.

The shrink tube we use for repairs has a glue that melts inside the tube and flows out to provide a positive seal. It's not always available at the hardware store but most Parts Dept.s carry it.

There's also such a thing as a solderless repair butt connector that has shrink tubing built in. Crimp... heat... done. You'll probably need a short section of wire to splice into the damaged area once the wiring is cut back enough to get to good copper, so figure on getting enough supplies to splice twice.
I had a chance to check NVLD action out with a voltmeter today and this is what I found...

The signal circuit runs around 10v with the switch open (no vacuum in system) and about .7v when closed. These voltages varied a bit depending on actual system voltage, running closer to 9v/ .4v earlier before running the engine and attaining a higher state of charge.

The actuator circuit is 0v when off and roughly 5v when actuated and actuation opens the NVLD for venting. The PCM outputs a higher amount of current initially to get the vent valve to actually move, then cuts back on its current to hold the vent open. The whole thing happens so fast that it's hard to see the initial "bump" current, but it seems to run around 9v before dropping back into the high-4v range.

Customer: replied 5 years ago.
I spliced the wire this evening and so far there is no CEL or GASCAP message. How long until I should consider this solved?
I like it!
To have the GASCAP prompt turn off it means the system has seen at least one Good Trip. There is no way to kill the GASCAP prompt artificially and since you're enjoying a respite from this horrible nag... I'm optimistic that it's fixed.

The next few days will tell the story as the system takes its measurements while you drive AND while you sleep. How creepy is that?

For now, cry some happy tears. I think we've cracked it!

Dodgerench and 5 other Chrysler Specialists are ready to help you
We good? Woohooo! :)
Thanks bud. Much appreciated and it was a pleasure working with you.

Happy trails!