The replies already given in this thread provide most of the relevant information. If you have not previously seen the FSM link below, it is worth a look because it has sections for most LC100 model years including the various combinations of engines and transmissions in USA and elsewhere. There is so much commonality with the LX470 that the differences do not matter except for bodywork, trim and accessory details.
On AHC matters, there are three places which can be helpful. These are:
A General Description of the Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) systems and how they are meant to work. This 20-page description has good diagrams and explanations of each of the component parts of these systems. The hydraulic circuit diagrams are helpful when trying to visualise issues. This section is descriptive rather than diagnostic. It is worth printing for a careful read and later reference. This General Description is found easily at
https://lc100e.github.io/manual/
then follow the index tabs starting right at the top:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension.
AHC/TEMS Diagnostics is a very important section and diagnostics are well-covered at the same FSM link --
https://lc100e.github.io/manual/ -- via these tabs:
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS
This section takes you to the Diagnostic Trouble Codes (DTC's) you are seeing. The "Problems Symptoms Table" also can be useful.
The “On-Vehicle Inspection” and “Adjustment” sections contain most of the AHC/TEMS procedures and specifications for setting up or adjusting the suspension. These are found at the same FSM link --
https://lc100e.github.io/manual/ -- via these tabs:
Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ON-VEHICLE INSPECTION
Repair Manual > SUSPENSION AND AXLE > ACTIVE HEIGHT CONTROL SYSTEM > ADJUSTMENT
It is not relevant to your current issues but this last section includes the actual FSM vehicle operating height specifications. This are quite finnicky to measure. Instead, IH8MUD Members including
@PADDO have recommended the following well-known operating height approximations for vehicles in as-built stock condition:
Front operating hub-to-fender distance: 19.75 inches (about 500 millimetres)
Rear operating hub-to-fender distance: 20.50 inches (about 520 millimetres)
These measurements are independent of tyre size but will be different if the vehicle has been ‘lifted’.
It is very late here -- 12:53 am Tuesday morning -- tomorrow I will have some time to read through this thread and possibly offer some further thoughts.