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Discussion Starter #1
Coming down the highway yesterday, the car locked all its doors. I hit the unlock button and it relocked instantly. Now it's locking all the time. I figure it's probably the CCM wiring under the seat as my dome light has never worked since I got the car. Sound about right, Or do I have a bigger issue?
 

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or problematic door panel lock/unlock switch, internal latch status switches, moisture in a harness or connector, etc...

I'm used to the MkIV Golf/Jetta gremlins like this, although they auto-lock their doors when the vehicle reaches a speed of something like 7mph anyway... Does the Passat not auto-lock them at speed?

My previous Jetta Sedan, a 2001 model never knew the passenger door was open/closed so the dome light wouldn't come on and the "open door" dash indicator light wouldn't illuminate for that door and you could lock and arm the alarm from the remote with that door still open...

My current Jetta, a 2003 model has the same issue with the driver door which is most annoying because it also re-locks all the doors with that one still open if I don't get in and start the car or open any of the other doors within about a minute of unlocking the car with the remote or occasionally as it re-locks the doors it also triggers the alarm by mistake, plus when I arrive at my destination and open the door the dome light will not come on automatically because it doesn't know the door is open and in my case it's a latch switches problem, a known major issue, and a huge ordeal to fix...
 

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The Passat has auto-lock at 7-8 mph. It is coded and can be disabled with VCDS from what I have heard.
 

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Discussion Starter #6
Well, I don't have a key fob, it came with one but its been gone for years.

The car has never auto locked before and will do it parked, going down the road, at 10, at 70, it dosnt care.

I've got moisture on the inside of the windows so I know I've got moisture in the carpet from all the snow.

Lots of fun!
 

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If water got into the driver door panel armrest switches and/or the passenger side lock/unlock switch it will cause intermittent problems like that.

Occasionally one or more of the window and lock switches in the driver armrest switch panel can also go melty and cause intermittent unwanted operation.
I've also heard a few people talk about the chassis wiring harness section that runs from the body into the door getting pinched somehow or fatigued within the loom and causing random shorted wires relating to the windows and/or locks although that doesn't seem to be one of the more common failure points.
My previous Jetta's fuel door would randomly open or not open when I needed it to for the first few months I had that car and the previous owner had been fighting the problem for several years. A new door panel trunk/fuel switch totally solved the possessed gas door problem for me.

It might be unrelated but does your "door open" dash indicator light operate correctly for each door?

Besides flaky door panel switches and latches I've also heard of things like low battery voltage, weak ground connections under the battery tray, jump starting some Mk4 Golf/Jettas or even disconnecting and reconnecting their battery causing odd window and lock behaviors and a few B5 and B5.5 Passat owners on the TDI forums have chimed in that their Passats also had such gremlins randomly although I've never experienced that with any of the 3 different Mk4 Jettas I've had and I still don't have my 2003 B5.5 1.8T Passat wagon in my possession yet that I just bought 3 days ago from out of town with a leaking water pump so I have no personal reference for them yet...
 

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Oh, so you put the key in the door to lock and unlock it?

Does VW have a power lock switch on the keyhole that triggers all doors to lock or unlock if you double-turn it or something like that?
If it does, since it seems that you use the key in the door a lot, maybe that switch is getting tired?
I know that holding the key to lock or unlock rolls the windows up or down but can you trigger a power unlock of all 4 doors with the key in the driver door keyhole? If so then that's another thing to investigate.

If there are intermittent switch signals I would think that the car would log them as implausible or intermittent locks signals and possibly even indicate what source switch is causing it with a VAG-COM scan?

I know that it would log that my CCM had intermittent and/or implausible trunk switch signals when my jetta wagon's hatch button above the license plate went bad and would basically get stuck in the pressed state for random periods of time.
 

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I've had a diode go bad before in a rear door puddle lamp that triggered the alarm every few minutes and prevented the car from being unlocked with the remote. Cost me 50 cents from Radio Shack.
 

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My Passat door locks have been possessed by demons for years. Just opening the doors will trigger the doors to lock. The automatic locking feature with the car moving is so random it's funny. I can drive the car for 20 minutes or more and out of the blue they'll lock with no warning. When I stop the car and hit the master unlock switch, the doors will sometimes automatically relock. I may have to hit the button several times before they stay unlocked. It's become a running joke when I have my wife and mother-in-law in the car and I can't get the doors to stay unlocked.

I have replaced the drivers' door lock mechanism, but it hasn't really made any difference. I need to check the wiring to the CCM under the carpet, but I just haven't found the time to fool with it. The doors lock and unlock just fine with the remote, although sometimes I have to hit the unlock button a few times to get them to stay unlocked. If I start the car to let it warm up on really cold mornings I have to leave the drivers' window down or else my keys could end up locked in the car with the engine running. When the weather warms up I'll pull the driver's seat and look under the carpet and see if there's any wiring issues. I need to work on the wiring for my aftermarket stereo anyway so I can kill two birds, etc.
 

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It could be the other door's lock switch too, among other things...
Something's forcing a lock command when you trigger the unlock function, leaving it active almost continuously, and it's getting in the way of the motion auto-lock function.
I'm pretty sure Vag-Com will show signal errors to/from the ccm although I'm not sure about the pre-CAN vehicles...
My Jetta wagon's hatch was nearly impossible to open without turning the key in the lock, all sorts of wierd behavior and signal fault codes and I kept being told my CCM was bad but if I left it alone for a while the faults would stop showing and it would just work properly once or twice until I tried to open it more than once or twice without using the key. In my case the button would get stuck in the pressed state after triggering the hatch release and eventually would un-stick itself after a combination of time and bumpy roads. A new hatch release button above the license plate solved my hatch release problem and all my CCM signal fault codes disappeared.

In your case there are 2 door lock buttons (or is it 4, I forget), a keyhole switch, and other possible gremlins in the mix.
I still think Vag-Com should read the CCM and tell you which door it thinks the erroneous signal is coming from and you can go from there.
 

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There's a master lock button for all doors and there are individual buttons on each door. I've got a VAG-COM and I don't recall seeing any errors with regards to the door locking mechanisms or the CCM. I may have to run another diagnostic and look specifically for errors in those areas. It's been a while since I needed to use it on my Passat. I had to use it to release the electronic parking brake to change the pads on my wife's A6 and my daughter's A7. LOL, I think I'll be buying nothing but VWs and Audis in the foreseeable future just so I can keep using it.
 

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What year is your Passat? I'm wondering if CAN-Bus makes a difference for what codes it can and can't detect, which I assume came to the gas Passat in 2002 like it did the gas Golf/Jetta?
 

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As a '99 I'm assuming it's Pre-CAN-Bus so apparently the newer years' CAN-Bus system provides a bit more info on CCM stuff like that based on the codes my '03 CAN Jetta wagon provided while it had the bad hatch button.

In the 1.8T Golf/Jetta I'm almost positive that CAN-Bus was introduced in 2002 while I know that the TDI equipped Golf/Jetta didn't get it until the 2003 model year in the same platform/model car and it seems unlikely than a 99 Passat would have it that much earlier but with VW anything's possible and my B5.5 is a 2003.

Even in a '99 I would think you could monitor switch signal states in vag com although I don't know if it can distinguish individual door switches pre-CAN...
I know you can see the brake switch(es) state, cruise buttons' state, and stuff like that, I think including the horn button too in VAG-Com on a pre-CAN car as I did it in my last '01 Jetta so hopefully it can show you if it thinks one of the door lock switches is being pressed and which one, which might be the switch but could also be a damaged door loom harness section too...

I'm not sure how much (if at all) the latch mechanisms play any role in the locks' state signaling as I've never had the need to stare at the bentley door locks' wiring section so far and I don't know how similar my Golf/Jetta Bentley's diagrams would be for the Passat anyway.
Now that I own a B5.5 Passat I need to find a Bentley for it but that's not very high on the to-do list until after I take delivery of the vehicle...
 

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The CCM CAN-Bus system used in the B5 years is not compatible with the system used in the B5.5.
I don't believe there was any major change to the power train CAN-Bus between 98 and 05.
 
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