Discovery 2 Series, rear suspension

You could still have something that is failing and not throw a code. It happens sometimes if it is part of a system or if it is still within specifications range.

Check the relay in the engine compartment.
The compressor motor is behind the left sill.

Here is a Diagram of the rear suspension and a diagnostic check list for the compressor.

There can still be trouble codes that will come up when scanned, even when dash malfunction light fdoes not come on.
LanD Rover has a propietary scanner, so you will have to go to a dealeship to get the trouble codes pulled.

If you need any furhter help, please let me know.