Where's the evap Vent valve???

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heartfulaluv

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06 Liberty Limited 3.7
I got a "P0499 code - an Evaporative Emission (EVAP) system vent valve control circuit high,"
I tried searching for the vent valve location, and all I kept coming up on is the Purge Valve.. I kno that the vent valve is supposed to be located near the canister, in the under back, but can't see it, or anything near the canister that has wires going to it. What I believe im seeing, us the leak check valve...(Second pic)a three prong connector. From what I've come across, the vent valve has two prongs. There's reference to it being attached to the canister, but I saw nothing attached to it with wires.
 

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Shankster

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I just replied to your other post. That's the leak detection valve in the middle photo. Not sure what you mean by vent valve - isn't that the same as purge valve? Which is up in the engine bay to the side of the battery?
 

Shankster

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Those hoses actually look pretty good - a lot better than mine were. Are there any cracks in them?
 

heartfulaluv

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No, no noticable cracks .. the purge valve is in the engine bay. It chks out fine when I test it using a bidirectional scanner. The code, 499, indicates a high-voltage fault in the Evaporative Emission (EVAP) System Vent Valve Control Circuit.
The LDP is what I have. Ive tested it, when in the key in the on position, it gets no power, and has 7.5ohms resistance in the coil, which us what it should be. It doesn't have power unless it meets certain PCM parameters. So it appears to be functional. So now I'm totally lost as where to go from here. The code will not go away... I've reset the system, by means of draining the electrical system. I've done that several times... I've also erased the adaptive memory, via bidirectional scanner, several times, and erased the code via cheap obd scanner.... No go! It never erases... It just stays in there. I've never had that happen before. NEVER.
I have checked everything, relays, fuses, wires, from one end to the other, hoses, connections, everything, and have found nothing. The code stays, and there's the weird sound that I have no idea what it is...
.https://youtube.com/shorts/phw5zW0y-rU?si=WSrz-Tw3HhytxVpy
 

Shankster

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Hmm, dunno. As far as the sound it sure sounds like a pump of sorts and the only pumps back there I can think of would be the fuel pump and the leak detection pump. Can you have someone else shut off the engine while you're under there with a finger on that LDP (or leak detection valve as some seem to call it)? If that's what's humming I'm sure you could feel it. If that's not it maybe open the gas cap and if the sound is louder I'd think it would be the fuel pump. Hopefully someone else will chime in who's had a similar experience. I'm all out of ideas. Hopefully it's not your PCM gone bad as some suggest for that 499 code.
 

heartfulaluv

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Thanks for replying... Nope, I'm on my own. I'm going to unplug the LDP and start it, and see if that makes any difference. Trippy thing is, I can't clear the code... I've tried with erasing the adaptive memory with the scanner, and just erasing it with a generic scanner .. both claimed that the attempt was successful, but the MIL stays on. I've reset the system by disconnecting the battery and putting the cables together, both long term(overnight) and for like 15 minutes. It will not leave. As soon as the battery is reconnected, it shows right up. I've been resetting this way for years, on both my jeeps, and have never had this issue .
 

Shankster

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That is weird. I wonder if that points to a bad PCM? I recon you should always be able to reset a CEL, at least until you fire up the vehicle again.

Or I wonder if turning the key to "on" fires up the LDP briefly (which might make sense since the fuel pump will come on momentarily and pressurize the system), which I assume you'd miss with your multimeter? And the issue immediately triggers the CEL again? Just spitballing here - really have no idea.
 

heartfulaluv

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Rite? It's insane! Im going bonkers chasing this code, so I can remedy it ASAP, as I have California emissions past overdue!
Weirder thing is, I keep getting new, random codes pop up, then disappear! All have been irrelevant to the 499 code... I've quit chasing them though.. I'm able to erase them, although I don't totally discard them. I don't want one coming back to bite me in the **** and make me feel a fool for over looking it.
Im tripping in that sound... I've been starting and restarting that Jeep so many times I'ma fry my ignition switch!
The loudest area I've found it to be, is under the cover, where the filler tube is. It's loud and clear rite there. I've checked the cap and seal, although it can't make the sound, I wanted to make sure it wasn't contributing to it. There's no apparent vibration that I can detect, as I hold the gas cap. The thing is, don't think there's anything along the filler tube that could make such a noise.
The sound could be generated somewhere else and travelling up the filler tube? Fuel pump has definitely become a possible suspect, but why wouldn't I hear it when I'm closer to the tank?? Grrrrr. I really dont want to go there. That's waaaay more labor intense then I want to think about. I dont mind putting in the work, even though I'm a woman, turning 69 in two weeks, lol, but most of my tools aren't in my possession, there in my storage, 70 miles away! It's a full circle, I can't drive my Jeep out of town, til I get it fully legal, ie, smog certified, and I'm having issues that require more tools then I have with me, cause they're out of town! Every month that goes by, is costing me $255 for storage, and accumulating registration penalties!
Sooo, that being said, there is a lot more motivating me, then just having my Jeep running as it should....
 

Shankster

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I guess the sound could be the fuel pump then. Doesn't necessarily mean it's bad though. The fact that it stays on a while after you've shut the engine off might indicate a fuel leak, since it might be struggling to maintain fuel pressure? The vehicle runs OK though, right? And no obvious fuel leaks, right?

All those random codes you're getting - just wondering if it means you have a bad Powertrain Control Module (PCM)? which might explain everything else too???

You're not getting a whole lot of input on here - you might post your question on lostjeeps.com too. Hopefully someone will show up here or there that's been through something similar.
 

Shankster

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If it was your PCM there are services out there that can fix it - I've never done that but it doesn't look to be super expensive:

I once had a Ford PCM/ECU go bad (car would randomly go into limp mode and all the instruments went bonkers) - bought a used one off eBay and took the vehicle and used ECU to the dealer and they pulled the data off my old ECU and loaded it onto the "new" one and installed it - worked like a charm and my daughter is still driving that car 20 years later. As it was my wife's daily driver at the time we couldn't have afforded the couple of weeks it would have taken to send the old ECU out for repair but that might be your best bet (if that is indeed what the problem is).
 
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heartfulaluv

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Since my last post, I have ran into big issues. I started getting random fault codes, then the ESP BAS light, then the Traction control light,then the air bags light, and the Abs light, in the midst of trying to get rectify the first couple tasks, using a bidirectional scanner, I started getting the can bus error. It was intermittent at first, then stopped the scanning, due to the can bus unable to communicate. I threw my hands up and came into the house, before I lost it. I spent the whole evening, through the morning, trying to figure out where to go from there. I started out by checking the data link port for resistance between the can bus, high and low end, checking the power, and the grounds. The can bus resistance was 54, there was power, but only pin 4 was actively grounded. I started checking the body grounds, even though I pretty much kno they're going to be fine, since I recently spent three days scouring the jeep , finding messed up grounds and fixing them. The guy that I bought the Jeep from, painted the vehicle, grounds and all! I addressed some of them a few months back, but found more. I spent hours sanding down past the paint AND primer!
Here's the issue that stopped me from going any further, I have no wiring diagrams for my vehicle! Im simply using logic and hoping there's some things similar to the ones I have, of the other KJs.
I never have any issues starting it, or driving it. It's always started up immediately, and had no misfires, hesitations or anything! I literally fell apart!
I was freaking out! I had no idea what to do next... Then I went out to write down the fault codes that were still stored and showed up in the reports I saved with the scanner, and it started! I turned it off and started it up several times, then wrote down the fault codes, and came into the house And called it for the day. I had to focus on the Can Bus messages, beings I couldn't do much with no ability to scan, or start the Jeep. I did lots of research on these can bus errors, and realized how most of the fault codes popping up, were most likely in error, as a result of the communication errors. I went back out and tried starting the Jeep, and once again it wouldn't start, so I started going through connections and where I could easily access the wire harness, looking for bad wires, or bad connections. Its kinda dumb to go looking for things in areas that haven't been disturbed, so I focused on the places I'd recently done anything recently. I carefully checked everything near or around the BCM, (I recently been trying to deal with lighting issues, and the BCM was the weak link. During that time, I had removed, cleaned, and replaced all the BCM connectors, and all the connections around it.) i couldn't find any visible issues. I tried starting the Jeep, and it started. I connected the scanner, and it lit up, then as I went to get into the Jeep, I saw that the scanner was no longer lit! I started jiggling wires down by the connections under the BCM, and the lights on the scanner were flickering off and on. I noticed that the harness connector, close to the hood release, was a little loose, and caused the scanner lights to flicker, so I decided to look closer at it, and see if maybe I hadn't connected it tight enough, the time I had redone everything. Low and behold, the plate inside that held the wires in, slid back a little, allowing a better, tighter connection. I reconnected the battery, and the Jeep started, and the scanner worked. I checked everything else, lights, doors, radio, etc everything worked, and no more dash warning lights, and no current fault codes. It still makes that weird noise, but scanned it three times, and no codes.
I'm going in a bit to drive it, and see if anything comes up. Weird, I used the bidirectional scanner, and the basic scanner, and no codes, but the MIL light is in... Hmmm not gonna worry about it unless I get codes to go along with it... I'll keep you posted.
BTW I chose to go on and on about it all, in case it'll help someone else some time. It's the random posts and information that I collect, that helps me diagnose my stuff.... Like I read that the Can Bus wires are always, or at least should be, twisted. That helped me a lot when I was checking the wiring for that Can Bus errors...
 

Shankster

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That would be great news if it was all just caused by a loose connection. I guess you'll still need to get rid of that CEL for your emissions test though. If you can't do it with the scanner hopefully you can get rid of it by disconnecting the battery terminals and clamping them together overnight.

And thanks for following up with what is hopefully the final solution - it's so frustrating when folks don't do that.
 

sota

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once you found the loose BCM connections, it's time to clear all codes and drive it for a bit.

and don't be surprised if the LDP/ESIM goes out on you sooner rather than later.
these rigs are getting old, the LDP/ESIM are in a harsh environment place, and they're going to go bad.
 
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