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Discussion Starter · #1 ·
My car just turned 142k, and I'm slowly fixing vacuum lines as they break, so when I got a CEL on the way to work today, I was sure it was another vacuum line giving me trouble.

Turns out, it's p1476: Leak Detection Pump insufficient vacuum, which is not a simple vacuum leak. From what I've read so far, the pump can be bad, the pump can not have power, the pump can be dirty, or there may be a bad line going to/from the pump.

Before I tear it apart tomorrow, the pump is on the driver's side, yes? I'll check my Bentley before I get into it, and I'll post my success here (yes, success).

If anyone else has had and tackled this problem, feel free to chime in! I need to get rid of the code to pass New York State Motor Vehicle inspection...
 

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Discussion Starter · #2 ·
I haven't seen a detailed diagnosis of this yet, so when I tear into it, I'll take pictures for future reference.
 

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Hey bud, I had this one before when I removed evap components and had to put it all back in to pass PA inspection this week.

Assuming you have a 225 like mine, you will have two hard vac lines that terminate in the passenger side rear corner of the engine compartment (easiest thing is to removed hard charge pipe and even strut bar for best access. From the bottom of the Evap canister a line will run back to one of these connections, while the other comes off the little block of connectors where the fuel feed / return lines connect (right near coolant ball).

I had this code for a while since I just put vac caps on everything I deleted and no parts were actually bad. Let me know if you want me to post some pics, but your diagnosis of the possible root issues sounds spot on to me... I believe, the system which is complaining is actually hidden behind the passenger side wheel liner and consists of two blue balls :cool:
 

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Discussion Starter · #5 · (Edited)
Getting into this today. My check engine light went away on Saturday, then came back on Sunday, so I'm hoping I just need a good cleaning or a new filter. Pics to follow!

Edit: The reason it took me a week to get to this is because I got a wicked stiff neck last Tuesday, and it just started to go away yesterday. Of course I spent my free time yesterday rotating the g/f's tires and changing her oil (which hadn't been changed since May 2012!:banghead:).
 

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Discussion Starter · #6 · (Edited)
Edit: I read a post that said it was located in the rear right wheel well, but I either misread or was misinformed. The LDP lives in the front right wheel well on my car. I love fixing broken grounds, though, so this post is still somewhat relevant.


I think I may have found my problem:

Rear right wheel well:

Liner removed:

This should probably be connected:
 

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Discussion Starter · #7 · (Edited)
So, that didn't solve the problem. Looks like I'm looking for leaks and taking more stuff apart. One thing I did realize, though, is that going into VCDS and testing group 071 MAKES THAT NOISE IN THE BACK OF THE CAR THAT I'VE BEEN WONDERING ABOUT FOR YEARS!!! Apparently it's just the sound of the plastic gas tank getting pressurized/depressurized by the Leak Detection Pump.

Moving on...
 

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Discussion Starter · #8 ·
So I got the inner fender liner off the front right, and there's my LDP, sitting pretty. I sprayed a little PBlaster on it before I started taking stuff apart:



After getting one hose off, I decided to get the electrical harness off next, and I had planned to take the other hose off as well, until I saw this:





I decided to clean it up, reconnect, and run the test again: System OK!

I took a quick look at the fault codes as my CEL was still on, but it only showed P1476 (intermittent). I'm hoping this will conclude my story. I'll update when the CEL stays off.
 

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Discussion Starter · #9 ·
CEL turned off when I fired her up this afternoon. Went to put $20 in gas in her, and still no CEL. Since it already went away for a day and came back, I'm not 100% sure this is fixed, but I now have newer tires and can technically pass inspection. Yay!
 

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So, that didn't solve the problem. Looks like I'm looking for leaks and taking more stuff apart. One thing I did realize, though, is that going into VCDS and testing group 071 MAKES THAT NOISE IN THE BACK OF THE CAR THAT I'VE BEEN WONDERING ABOUT FOR YEARS!!! Apparently it's just the sound of the plastic gas tank getting pressurized/depressurized by the Leak Detection Pump.

Moving on...
This needs to be starred and thrown up as a sticky haha! I've been wondering what that knocking noise was, I always thought it was just gas sloshing around, but this makes more sense. You're doing god's work my friend :thumbup::beer:
 

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Discussion Starter · #12 ·
And the cat came back, the very next day...

Ok, so it's not the very next day, but after getting my clutch installed and driving around for two days, this CEL popped up again with just the p1476, so I'm back to diagnosing. I checked the electrical connection again last night, and I don't think that's the problem, but I haven't checked for vacuum leaks either. I'm still trying to figure out which hoses to check (other than the obvious two leading to/from the LDP).

Funny thing is, the code disappears every couple days and subsequently turns off the CEL. Any ideas?
 

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It may be the pump starting to go bad. If it was a leak, you would probably get an evap gross or small leask code. You could purchase a used one from a wrecker with a good return policy. Test it, and if that's not it send it back. It'll cost you a 20% restocking fee + shipping but probably worth it.
 

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Discussion Starter · #14 · (Edited)
Thanks! We have a few auto recyclers here in Buffalo that are pretty cheap for stuff like this, so I'll look into replacing it. I'm also going to test the resistance between the pins to see if it's the LDP. I feel like it should still be good, because it still pressurizes the tank like it's supposed to when I do the tests in VCDS.

I should mention that I definitely smell a gas-like odor in the car that wasn't present before, and while cleaning up the garage after my clutch install, I found a small piece of vacuum hose wrapped in black cloth. It was only two inches long, but does this look familiar to any of you?



 

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Discussion Starter · #15 ·
I checked resistance between pins 2 and 3 as well as pins 1 and 3 and got exactly what the Bentley suggests:

2 and 3: 16.2 Ohms (15-17 expected)
1 and 3: 670 Ohms (640-720 expected)

Looks like my vacuum lines are to blame, or a bad N80 or N115..
Also, the hard plastic lines that run from the LDP to the engine bay are fine with no cracks or leaks.
 

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I think even though the Vag Com pressure test passes, it could still be the pump on it's easy out. 070 or 071(can't remember which) tests how long it takes the pressure to go down and not how fast it pressurizes. So the pump could be slowing down and achieving pressure really slow. But it's still eventually reaching the correct pressure to finish the test. I think there's a foam filter on the pump you could check as well. Evap problems can really suck......
 

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Discussion Starter · #17 ·
I checked all the lines in the engine bay for leaks, and found none (I also don't have any lean condition codes or unmetered air codes; just the p1476). This leads me to believe it's a leak in the rear of the car, especially since I've been smelling gas vapors. Yesterday I replaced the gas cap for the heck of it ($7 at Napa). I heard the LDP functioning on my way home from karaoke last night, and the CEL turned off when I left my girlfriend's house this morning. I'll keep you guys posted.

Also, N80 clicks like it should.
 

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Discussion Starter · #19 ·
Still no codes, and I've heard the pressurization of the tank at least once since my last post.

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