AHC Height Offset with New Launch OBDII Tool (1 Viewer)

[OregonLC]

Okay, help me figure out what I'm doing wrong. 2016 LX. Have the front pretty even L/R. The right rear started 1" high (as measured from the ground).
This is the starting reading:

So I subtracted 0.25" from RR.

This did move in the right direction. The RR AFTER value decrease from 0.1 to 0.08. And the RL AFTER value went the other direction from -.11 to -.08. Both were in favor of what I was trying to do, however the RR height adjust value went the opposite of what I entered. It was at -.03. I entered -.25 which should have resulted in -0.05 (values are shown in feet. So each 0.01 ft ~ .120"). But rather than it going down to -0.05, it went up to -0.01. Most likely some sign change with the data entry.

So I repeated and indeed it came up from -.01 to 0.01. The same 0.02 positive adjustment from a -0.25 entry.

But... now I've got something else going on. It will cycle from N to H in the driveway, but will not change the N to H in the center of the AHC icon. The up arrow and H flashes, but it won't show 'H' unless the N-> H change is made while driving. It does restore to N at 19 mph. But the weird thing is that when on the highway, transitioning through about 67mph the nose will take a pretty good drop. I'm guessing this is the speed at which AHC slightly lowers the vehicle for highway stability. The drop is quite abrupt and very noticeable. Nothing crazy set on the front end, just a a minor L/R adjustment to event the height. I feel that I may have encountered a FA/FO moment.

Am I off on my strategy? Are my settings out of the acceptable range? If there's 0.8" of available offset, that's 0.067 ft and I don't see where I would be close to that.

 

[lx200inAR]

I would read the FSM On how to properly use the HOU. It does not work the way most people give directions for. There is more to it than just entering different numbers. The truck is also factoring in what the last height change it measured before using the numbers you entered. It’s definitely possible to get the offsets to max out, but it’s not as strait forward. The details of what values work and what dont are outlined in the FSM.

 

[grinchy]

Drive around the block after each change.

And like teckis said, change in rarely equals change out.

The computer does it all differential, and it won’t make changes at all if the number exceeds some opaque limits

 

[OregonLC]

Thanks for the replies. As far as the FSM procedure, it doesn't do much in the way of providing assistance other than to 'follow the instructions on Techstream'.

After my original post, I did some data logging to better understand how the adjustments were affecting the vehicle. Some observations:

This was done with the engine running, vehicle in park, parking brake off, level surface. The truck does have a max sensor lift.

1) While the tool allows you to make multiple adjustments, I didn't find that these always took. The tool would confirm that change but you should see/feel/hear the AHC make the change. I found that after each single change, you needed to cycle the vehicle N->H->N before making the next entry. You can see that in the data set below where a change value was entered, but no response.
2) Changing one corner affects the others slightly. This is reasonable as the load has to balance across all four. While the AHC should be adjusting pressure as required to achieve a sensor position, this isn't absolutely perfect.
3) As was stated by others, to get a true and final reading the truck needs to be driven. While we're only making small adjustments, the IFS moves through an arc and tire bind will affect the final position as well as road bounce.
4) I need to play with it more but I wasn't successful at dialing out the 1" height delta in the rear.
5) The display is in ft. Even with two decimals, this isn't a great resolution when you're entering 0.25" change values.

The truck now will achieve the 'H' icon when raised in the driveway. I haven't yet driven on the highway to verify the 'Fast' lo operation, but I suspect it will work. I think part of my problem was trying to use the height offset utility (HOU) to achieve a slight additional gain in height without using mechanical means to normalize pressures, i.e. spacers. I'm going to forestall that until we get into warmer weather but it's high on my list.

 

[lx200inAR]

Thanks for the replies. As far as the FSM procedure, it doesn't do much in the way of providing assistance other than to 'follow the instructions on Techstream'.

View attachment 3825728

After my original post, I did some data logging to better understand how the adjustments were affecting the vehicle. Some observations:

This was done with the engine running, vehicle in park, parking brake off, level surface. The truck does have a max sensor lift.

1) While the tool allows you to make multiple adjustments, I didn't find that these always took. The tool would confirm that change but you should see/feel/hear the AHC make the change. I found that after each single change, you needed to cycle the vehicle N->H->N before making the next entry. You can see that in the data set below where a change value was entered, but no response.
2) Changing one corner affects the others slightly. This is reasonable as the load has to balance across all four. While the AHC should be adjusting pressure as required to achieve a sensor position, this isn't absolutely perfect.
3) As was stated by others, to get a true and final reading the truck needs to be driven. While we're only making small adjustments, the IFS moves through an arc and tire bind will affect the final position as well as road bounce.
4) I need to play with it more but I wasn't successful at dialing out the 1" height delta in the rear.
5) The display is in ft. Even with two decimals, this isn't a great resolution when you're entering 0.25" change values.

The truck now will achieve the 'H' icon when raised in the driveway. I haven't yet driven on the highway to verify the 'Fast' lo operation, but I suspect it will work. I think part of my problem was trying to use the height offset utility (HOU) to achieve a slight additional gain in height without using mechanical means to normalize pressures, i.e. spacers. I'm going to forestall that until we get into warmer weather but it's high on my list.

View attachment 3825733

The "Notice" in yellow at the top is the calculation that has to be within range. Doing a N -> H -> N should be resetting that "Height after adjust" field to 0. There is more to it in the FSM with a section describing how to set standard height. It involves jacking up truck to make measurements from certain suspension components to be within a range. Then the ECU uses that after adjust value to know how much you had to jack the truck to get to the right height.

 

[skrypj]

I’ve screwed around with the HOU with my launch tablet as well and rarely get it to do what I want in one try. I did get 0.9” of lift and then was able to get it back down to the original offset.

That said, my 2018 has always been a bit finicky about changing height. Sometimes it wants me on the brake, some times not, sometimes it likes park, sometimes drive. It will just sit there and flash the up or down arrow and not move until I figure out what it wants. It’s been like that since I bought it, before messing with HOU

 

[OregonLC]

@skrypj do you have a sensor lift? Any heavy accessories? Those symptoms seem to be related to either high AHC pressures, low fluid volume, bad globes, or contaminated fluid.

 

[skrypj]

@skrypj do you have a sensor lift? Any heavy accessories? Those symptoms seem to be related to either high AHC pressures, low fluid volume, bad globes, or contaminated fluid.

No. Just skid plates. I am at stock ride height unless I HOU lift it.

 

[eatSleepWoof]

Make sure you're playing with these adjustments on an absolutely, perfectly level surface.

When I went through my own AHC fiasco, the guy that finally got the truck level (Lexus master tech) stressed that it's absolutely imperative to do all AHC adjustments on an ice-rink-level surface.