The suspension ecu gets its main power from the 20A engine bay fuse which is required to operate the air valves and exhaust pilot valve. If this is removed with the ignition off then the ecu looses the current height status.

The ecu will use power from the passenger compartment ignition-on suspension 5A fuse to at least issue the '50 kph only' error message if the 20A fuse is removed but cannot be used to operate any valves. The engine bay relay is only to run the compressor and the 5A engine bay fuse is only to protect wiring on the 'compressor relay contact closed' feed-back circuit.