Auto Leveling System Stuck - Help!

On this Chevy Venture van, the rear air shocks pumped themselves up while the vehicle was being driven. They are now fully pumped up and won't come back
down.
With the ignition on, I can occasionally hear what sounds like a valve start to release air, but then a pump kicks on which, I assume, reinflates the shocks.
I've looked thoroughly on the interior of the van and can't seem to find an air shock release valve (there is an air inflation valve for the pump, but that does not seem to release any air from the shocks).
The weather is very cold (about 0 deg F.) and I'm wondering if perhaps a pressure sensor or something has frozen?
I'm not at all familiar with the system, and I'm hoping someone has experience with this problem and knows what to do to fix it. Is there a diagram somewhere that shows the layout of the system, etc?
Any help would be greatly appreciated!
VHarris
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OOPS, I forgot to put the year.
It is a 1999 Chevy Venture with the "Electronic Level Control" (ELC) Option.
Thanx
VHarris
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@aol.com says...

Check this: Auto Level Control (ALC) Sensor - Mounted to rear crossmember, above rear axle
Its a little box with an arm and linkage coming off of it. See if it came off and got stuck upwards. I'm guessing the winter weather and snow might have something to do with this. Back into any snowbanks lately?
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Thanks! The sensor was the problem. The linkage snapped at the place it connects onto the arm of the sensor, and the arm was stuck in the "up" position. I pulled the arm down and the air released from the shocks.
By looking at it, I can probably replace the linkage myself. But do you know if the linkage is a fixed length, or does it require adjustment? Can the adjustment be done by a shadetree mechanic, or does it need to be done by a dealer? Where can I get instructions on how to do the adjustment?
Thanks again, VHarris
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@aol.com says...

I'm not sure what the length of it was or if its adjustable. Sorry. I would take a measurement off of another one and make one that way. Put enough threads on the linkage and you can always go back and tweak it.
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I got from a dealer the link that goes between the Electronic Level Control Sensor and the rear axle housing. It is of fixed-length (not adjustable), with small ball-joint sockets on both ends. I would have guessed it would have come with the threaded ball ends already in place, but it didn't.
There are no instructions on how to separate the old link sockets from the balls, or how to press on the new link sockets onto the existing balls.
Does anyone know if I can just pry off the old, broken link sockets and use vice-grips to press on the new link sockets? Or is there a "special tool" to remove the old ball sockets and another "special tool" to press on the new sockets?
And can the R & R be done on the vehicle, or do I need to remove the ball ends from the vehicle to press on the link?
Does anyone know if a lubricant needs to be put in the socket before it is pressed on the ball?
I'd hate to botch up the new link installation.
If anyone has a parts or service manual, it is part no. 22153604.
TIA
VHarris
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FYI - update of the installation of a sensor link for the "Electronic Level Control" system on a 1999 Chevrolet Venture.
Block the vehicle up before working underneath it. If air is in the shocks, moving the sensor can release air and unexpectedly let the vehicle settle down.
The link part is actually GM# 22153552, not the number I incorrectly posted previously. GM's price is $25.12 plus tax.
The link does not come with installation instructions, but it does include a diagram of the correct orientation of the link to the sensor arm, so you won't install the part with the arm in the wrong position.
The ball sockets at both ends of the link are plastic. The link snapped at the place where the plastic is thinnest, right at the place where the ball socket narrows and is formed around the metal bar connecting the two sockets.
Other than the break, there was no visible damage to the old link or the sensor, and the sensor arm moves freely up and down. It was likely just a fatigue failure, contributed to by the very cold weather.
Using needle-nose pliars, I was able to easily pry the old plastic ball sockets off the metal ball ends without removing them from the vehicle. When working on the sensor, be careful to pry against the end of the arm. Don't apply force on the arm which can be transferred down the arm to the sensor. Also be careful not to damage the surface of the ball ends with the teeth of the pliers.
I used vice-grips to gently squeeze the new ball sockets onto the ball ends. Be careful to align the socket with the ball to minimize the amount of force required to press the socket on.
Thanks Bonneville for correctly diagnosing this problem for me.
VHarris
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Thanks to both VHarris and Bonneville for all of these leads. I have a low mileage 1998 Pontiac Trans Sport, with a bunch of add-ons, recently purchased from our recently widowed aunt ... it is much more than she now needs, and she downsized. However, there have been a few minor irritations that are a result of poor maintenance on the part of her dealer, who had the van in regularly, and charged her some outrageous maintenance costs. It recently refused to start, and when I got the cables off the battery, it was a wonder it got me home, from the amount of corrosion between the connectors and the battery! :^( However, I digress ..
My son borrowed the van this morning to visit his uncle, and bring home a lawn chair that his uncle had made for us for Christmas. When he arrived there he called to tell me that the car was riding very roughly, and the slightest bump nearly put him out of his seat. Oh, yes, and there's this constant pump noise in the back end ... don't know what that is.
I knew what the pumping noise was, and had him pull the #4 fuse block to turn it off [along with the power seat controls and the rear window defroster ... go figure!]
I'm driving over tomorrow morning (an hour and a half away) to recover the van, and I feel certain from your postings that you've already given me the answer to the problem. If I can release it alright, I'll bring it home here to where I am blessed by an independent, honest mechanic!!! ;^)
All blessings to you both, Brian Colgate Napanee ON Canada 2004 12 28
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