This just means that your height sensors are out of range and it dropped to the bump stops as a precaution.
To fix this, jack the truck up to "normal" height. Measure from the top wheel arch to the center hub cap of the wheel to 466mm (18 3/8") for the front and the rear is 485mm (19 1/8"), and then start the truck. If you have lift rods, you'll have to adjust your calculations for it. Once the suspension is within spec, it will pump air into the system. IF this works, recalibrate the suspension with the Gap IID Tool on flat ground.
The other way to do this is using your Gap IID Tool to put the suspension into "Build mode". Here's the excerpt from
https://www.gap-diagnostic.com/faq/.
Or, can the IIDTool help when the suspension becomes inoperative? Can it close any specific valve for any corner and keep it closed while you limp off the trail?
Yes. For example, when an air strut fails, the suspension ECU detects a major fault since it is not able to raise the corner. In some cases, it lowers all corners to the bump stops. The lowering may be caused by the air leak itself since on normal operation, corners are adjusted in pair.
To manually control the air suspension, proceed with the following:
- IIDTool Menu->Service Test->Suspension->Test Valve->Select the Front Axle only, adjust to the desired height
- IIDTool Menu->Service Test->Suspension->Test Valve->Select the Rear Axle only, adjust to the desired height
- Each corner can be adjusted independently if needed
Keep in mind that raising both axles using Adjust All is not recommended since it takes much longer to reach the desired height. This is because the pressure equalizes when all four corner valves are opened (air goes from the front airbags to the rears) thus increasing the time required to raise the front axle.
If you are raising the vehicle significantly, the compressor may need to cool down before it can pump additional air in the system.
Once the desired height is reached, exit Test Valve mode and disable the suspension: IIDTool Menu->Service Test->Suspension->Build Mode
When finished, simply put it back into customer mode by calling the Build Mode function once more: IIDTool Menu->Service Test->Suspension->Build Mode
Not raising all four corners will put the vehicle out of balance and this can cause a safety hazard. We do not recommend driving an unstable vehicle but it can be useful to recover the vehicle with a defective EAS while offroad. Do not drive an unstable vehicle at high speed.
