Take measurements of your ride height at each corner of the vehicle. I recommend measuring from the fender lip to the bottom wheel lip.
Turn off ignition. Locate the Height Control Sensor as seen in the diagram. Note the position on the adjustable top mount. You are going to want to slide it up as far as possible in the next step. For better access to the height control sensor, you can turn the wheels full left/right.
I found it easiest to just remove the top nut of the heim joint (10mm) and adjust the rod so that it is as short as possible. This will give you about 2" of lift in the front. If you want 2.5", you'll have to shorten the heim joint (I used a cut-off wheel) and then used the existing stop-nuts to "smooth out the thread" and actually remove the stop nuts completely. Be careful because one side is a reverse thread. Not many people I know have a reverse cut tap/die set. Once done, reinstall the heim joint and adjust it so that the Height Control Sensor lever is as high as possible. Remount the wheels. You can readust the sensor through the wheel-well later. Make sure ALL adjustments are done while the vehicle is OFF for safety reasons!
After the front sensor adjustments are done and all jacks are cleared away, you can start the engine. All the doors, hatch and hood need to be closed for the AHC to work. This adjustment will yield up to 2.5" of lift in the front.
Now for adjusting the rear. Again, make sure ignition is off. No need to remove the wheels, just crawl underneath and locate the Height Control Sensor. There is only one for the rear. If you slide the adjustment to the top, you'll gain about 1.75" of lift. For more, you'll have to extend the mount 2" or so. I used 1" aluminum flat stock and drilled two holes (to mount to the existing bracket) and slotted a 3rd hole for adjustability. If you space out the aluminum stock from the old bracket 3/16" of so, you can get better adjustability.
Fill Reservoir with AHC Fluid to correct level. It is also a good time to flush the system if its never been done before. Lexus recommends a flush every 60k miles. How to flush AHC fluid thread: Changing out the AHC suspension fluid? - https://forum.ih8mud.com/showthread.php?t=60619
Replace AHC fluid
This is how we usually do it at work (no rocket science), just be careful you don't squish your melon!! One can of the ahc fluid is usually plenty.
- Set the vehicle all the way to low (Reservoir full)
- Remove all of the old fluid from reservoir. Fill with new clean fluid, I usually put the whole can in. 3. Start vehicle and let suspension equalize to "n" position.
- Turn vehicle off.
- Start at one of the back accumulators (doesn't matter which one) and using a hose on the bleeder, open very slowly and let weight of vehicle push fluid out. Close bleeder when vehicle is close to bottom. THIS IS THE STEP YOU COULD GET SQUISHED IF YOU ARE NOT CAREFUL!!!
- Start vehicle and repeat steps for each corner accumulator.
- Usually one cycle at each corner is sufficient. If you are going to do it more than once you will need more than one can of fluid. Cautions - don't crack bleeders while car is running. Vehicle will try to compensate for the leaking corner and you will have a big high pressure mess. Fluid resembles very slippery brake fluid and is a PITA to clean up - so keep that in mind. Also this is usually PM at 60,000 miles. Questions let me know.