Does disconnecting the battery & reconnecting it help?

Hi. We have been trying to remove the battery. no changes

Very strange that the LEDs do nothing. If there is a malfunction, they should at least blink a couple of times. Any system malfunction should also produce the suspension inactive message on the dash. If the switch was bad the entire suspension would not go up and down. All the switch does is tell the control module that there is a request to raise or lower the suspension. The fact that 1 axle is responding is very strange.

You really need to hook it up to a GT1 to find where the fault is... with out it, it's all a guess

Here is an obvious question. Have you checked the rear springs and connections for air leaks?

When you push the up or down button mine does nothing, but BLINK & i have a SLS alarm on my insterment cluster. ???

So now I have done several tests. First I disconnected the battery for 10 minutes. no changes. Then I arranged the relay and connect it again, no change. Then I connected the diagnostic device. The controller detects any height sensors.

The computer measures a change in nominal ride height under load only the front left(when I step on the footboard ).

Front right, rear right, rear left are always 0mm difference to the nominal height.

Ok, now I think of course the height sensors are faulty. But why do they still change their voltage? :dunno:

Very strange. Did you check the height sensors. Are they damaged, or maybe bent on their mounting locations.

The air supply control unit is located in the spare tire area.

Always good to check the sensor units first, especially if the suspension has been fully extended for a tire change or other service work. The arms can reverse themselves and cause the system to show as inactive. The sensor units are attached to both sides of the rear suspension and passenger side of the front suspension. Note that once corrected the inactive reading does not go out until you have driven a mile or so.

Does anyone know if the voltage decreasing at the front suspension changes differently? I mean, on one side the voltage get higher when I lower the car. On the other side voltage get low when I lower the car. ???