Buick Repair Questions? Ask a Mechanic for Answers ASAP
The rear of the car has an electrical level sensor that signals a compressor and an exhaust valve. Your problem is either in the level sensor or in the exhaust valve. The exhaust valve is built onto the compressor. The compressor assembly is located at the passenger side rear of the car. You can connect a jumper wire between the white wire at the compressor assembly and a good ground with the key ON. This should activate the exhaust valve and allow the rear of the car to go back down. If grounding the white wire works, replace the level sensor. If it does not work then the exhaust valve is bad and will need to be replaced.
You can disconnect the air line at one of the rear shocks to release the air and let the suspension down to normal height. To keep the suspension from airing up again you would need to remove the ELC fuse.