2004 allroad rear suspension down
 

What level is the suspension at? Do you have the amber suspension indicator lamp on in the instrument cluster? Have you tried lowering or raising the suspension with the up and down buttons in the dash?

The suspension is at level 2.

I replaced the pump last year and then tried to reset the levels with the Ross-Tech cable. While doing that the system locked itself at level 2, the amber dash light appeared and I ended up just leaving it that way as it never sank. I could hear the pump run occasionally topping off the system as it should and I was satisfied to have the ride height stay at level 2. I know it's not the correct remedy but it had been working fine for a year.

However this has prevented the up and down buttons from working to raise or lower the system which would activate the pump.

Tomorrow is supposed to be well above the freezing mark and wondering if the valve block will thaw if frozen and allow the pump to run.

If the front suspension has not dropped to the bottom stops, my guess would be the air compressor is fine. Could possibly be a setting got changed when you were using vag-com. I doubt that the cold weather is responsible. Could also be a bad plug connection at one of the sensor blocks.

The car is finally at the repair shop. The rear suspension is still all the way down on the bump stops.
They ran the suspension level calibration, but said it would not complete as it never got past the "wait" point.
They said the pump ran when they tested it separately. Does this mean that the pump is not getting communication telling it to run and fill the rear bags?

These are the codes that they pulled.
01400 Level Control Sporadic: Resulting in limit not reached
01437 Control position not learned
01772 Signal from level control pressure sensor G291 sporadic: implausible signal

Any help is greatly appreciated, thanks.

Do you know if the wire connectors were checked at the level sensors?

Yes, possibly a bad connection.

Thanks to all who chimed in with help, it was greatly appreciated.

After spending quite a bit of time with my repair facility and more money than I had hoped, I once again have a fully functioning suspension system that hits all 4 levels quickly and easily. Once I convinced the shop that the level control module was bad (they initially thought I was a know-nothing) and had them replace it, it was just a matter of tracing all the weak spots that were popping up. So along with a bad module, they showed me that the pump was weak, the brown airline coming out out the pump was cross threaded, (I take blame for that one) and that both front level sensors up from were bad. They kindly let me see the info they were pulling off their diagnostics system so I could be sure they weren't just throwing parts at it. I just wish Audi had put the level control module in a more accessable spot, rather than buried in the side trunk panel. And better yet if this had been any time other than the winter I would have done the job myself. But at 195,000 miles you can't blame the system for being a bit tired.

Early on in the process the mechanic suggested that I go with the coils springs and shocks conversion as a way to avoid future trouble.I thought about it for a day but I just couldn't do it. It cost me more to keep it stock, but there's a certain joy in having that suspension to get you up and over most anything in your way.

Thanks for the update on your suspension. I would not have changed to coilovers either. Keeping the car original means more to me. Did you purchase new control module or used? If your air compressor is weak, bagpipingandy on the internet is a good source of parts and repair. I have been pleased with his service.