I did a routine code check on my E550 and saw the following code -
1 Airmatic (N51/3) Code - Status Confirmed - The time for filling the compressed air reservoir was exceeded.

I looked around the web and could not find much information. Is this an issue? Can I fill it myself?

Thanks.
2011 E550 with @ 100,000 miles

 

I remember seeing corrosion referenced at the reservoir tank connection with some Airmatic equipped cars. Yours may have a leak and the pump cannot keep up with the amount of air escaping so it shuts off per protocol and causing the warning.
No you cannot fill it.

 

Check lines @ valve unit (compressor), and reservoir (trunk), see attachments.

 

Thanks, I need to do some investigation and leak hunting. Where is the most common place for a leak?

 

The error is indication of compressor time-out, so it can be results of leak, or wear out compressor piston.
With 10 yo car on original suspension, air bags might be due for replacement. Observing how the car sags after parking might give the answer which corner leaks, but aged rubber can't be patched for long.