My rear driver-side air spring does not seem to inflate fully. It inflates a little which tells me the pump is working. It stays put which tells me there is no leak. I'm thinking the level sensor but not sure how to diagnose it.

It is hard to find any info on this because as soon as some one mentions 'air suspension' everyone responds with 'convert to springs.' I primarily use the truck to tow boats. I benefit greatly from the air springs and would like to keep them if it doesn't cost me an arm and a leg.

Any help is appreciated