How to properly test AHC and 4WD systems when shopping for a used 2013-2015 LX 570

[rustsatz]

I'm basically a newb to 4WD vehicles but I've always wanted to own an LC/LX. I was hoping for some pointers and maybe some simple procedures on how to check these systems out.

I do appreciate your time!

Thanks!

 

[doru]

Get the owner manual online for your year and familiarize yourself with the controls.
You usually don't have time to fiddle /discover during test drive. Use the test time to test.
I try to have one gravel segment in my test. Any side road or even shoulders on secondary roads.
The goal is to go through all the major settings like HI/lo range, crawl, HI/LO height for LX and see that all the controls function as expected, smooth, w/o strange noises, and produce the expected behavior.
Real testing would be nice for buyers but most sellers will not agree to it.

 

[kwelhand]

Not just AHC, 4LO… check the valley plate leak, radiator crack, etc.
it cost me $2500 to fix as soon as I brought my used LX from a local Lexus dealer… YMMV.

 

[zoned]

Get the owner manual online for your year and familiarize yourself with the controls.
You usually don't have time to fiddle /discover during test drive. Use the test time to test.
I try to have one gravel segment in my test. Any side road or even shoulders on secondary roads.
The goal is to go through all the major settings like HI/lo range, crawl, HI/LO height for LX and see that all the controls function as expected, smooth, w/o strange noises, and produce the expected behavior.
Real testing would be nice for buyers but most sellers will not agree to it.

 

[zoned]

Caveat to the no strange noises comment. Crawl control sounds like your vehicle is about to fall apart. That’s normal. Lol all other noises are not.

 

[borfoo3]

Already mentioned above, but this is what I would do during the drive:

For AHC:
1- Cycle normal/ low/ high heights (in that order).. Cycling should be smooth and can hold height.
2- While driving, hold decent speed and go through a speed bump (or equivalent). Damping over the bump should be smooth and not harsh.


For 4WD, 2 things to be checked on loose surface:
#1) 4Lo/ 4hi should be engageable without too much delay
#2 ) Center diff lock should be engageable without too much delay

If the above is ok, you could try get it inspected by a 3rd party shop with a hydraulic lift for any leaks...

 

[rustsatz]

Thanks for the guidance everyone. I went and checked out my first potential LX yesterday (2013 95K miles). Everything seemed in reasonable condition except the AHC. It wouldn't raise or lower consistently. And when it did, the front would drop and then the back. Is it safe to assume it is supposed to raise and lower evenly? I did pull the reservoir cover and did find that the fluid was below 'low'. This particular LX has had a consistent maintenance history throughout its life at a Lexus dealership, so I was quite surprised. Not being 100% confident yet in my LX diagnostic skills/knowledge, and knowing how complicated/expensive the AHC system is, I passed on the vehicle.

 

[grinchy]

Yeah, they raise a bit at a time. mine lowers pretty evenly (and very quickly, like 2 sec to go from N to L)

 

[PDoyle]

Thanks for the guidance everyone. I went and checked out my first potential LX yesterday (2013 95K miles). Everything seemed in reasonable condition except the AHC. It wouldn't raise or lower consistently. And when it did, the front would drop and then the back. Is it safe to assume it is supposed to raise and lower evenly? I did pull the reservoir cover and did find that the fluid was below 'low'. This particular LX has had a consistent maintenance history throughout its life at a Lexus dealership, so I was quite surprised. Not being 100% confident yet in my LX diagnostic skills/knowledge, and knowing how complicated/expensive the AHC system is, I passed on the

The AHC fluid is behind the passenger side rear wheel inside the wheel well and partially blocked by a plastic cover in a white plastic container. The only way to see fluid there is to get under the vehicle with a flashlight and cram it up next to the container. When in H mode you should see pinkish fluid at the min line.

 

[Mixelplix]

My AHC moves in stages too. When raising it seems to do a little of the rear, and then a little of the front - back and forth. It generally lowers both the front and rear at once.. but it makes small adjustments 10-30 seconds after it does it's major drop.

Remember the AHC won't move at all if any of the doors, or the rear hatch is opened.

 

[TR4RUNNER]

Thanks for the guidance everyone. I went and checked out my first potential LX yesterday (2013 95K miles). Everything seemed in reasonable condition except the AHC. It wouldn't raise or lower consistently. And when it did, the front would drop and then the back. Is it safe to assume it is supposed to raise and lower evenly? I did pull the reservoir cover and did find that the fluid was below 'low'. This particular LX has had a consistent maintenance history throughout its life at a Lexus dealership, so I was quite surprised. Not being 100% confident yet in my LX diagnostic skills/knowledge, and knowing how complicated/expensive the AHC system is, I passed on the vehicle.

I recently purchased a 08 LX 570 with 117K. I test drove 4 different trucks from 08-13. My 08 was the oldest but had by far the best service history (5k oil changes, every scheduled maintenance done at same dealer), and no rust. My AHC was slow to go up and still does not like to go into the low position but it works great going up to Hi and in 4Lo. Mine raises and lowers rear up first and front down first. I changed the globes and did a fluid flush 2x. I would be very surprised if the fluid level was below ’low’. It is very difficult to see the fluid in the reservoir, you need a powerful flashlight jammed up next to the spare tire with the beam pointing at the bottom of the reservoir. And if it is sunny and you are in your driveway you still might not be able to see the level of new fluid as it has a light pinkish hue where as old fluid can be dark brown.
I would encourage you to look at YouTube videos for LX 570 AHC. ‘Last Line of Defense’ has a good run down of a truck he purchased and goes thru many features including AHC. Sorry I can’t figure out how to post the link. Good luck

 

[lx200inAR]

As far as pre-inspection tests, another possibly good idea is to test the easy access function. This is the button that looks like someone getting out of a seat. With this activated (light lit on dash), when you turn the truck off it should lower to L to allow for easier exit/entry into vehicle. All doors need to be shut and you have to give it a second to happen after turning the truck off. I only mention this because recently there was a thread where the easy access function stopped working on an LX. It turned out there was a "hidden" DTC for a failed shock valving actuator that caused the function to stop engaging. In a perfect world you'd get a full Techstream scan on any vehicle before you bought it, which would uncover this sort of thing, but this is a sneaky way to verify there are no AHC DTCs keeping the system from fully functioning.

If the system was too low on fluid you would have gotten an alert in the dashboard pretty quickly. That's the one thing that does trigger a failure pretty fast that the computer picks up on. Not to say it might not have been a little low, but as other's have stated here, it's unlikely you were able to get a true gauge of fluid level just looking through the inspection cover in the wheel well.

My thoughts/opinions having bought an old LX recently-ish. If the pump is still working and truck can go up and down, even if not super smoothly, you are probably in the clear AHC wise. Then the next biggest thing to worry about is how rusty are the AHC components. That's the biggest killer of AHC parts.

For less than 1k and an afternoon in your driveway you can replace the accumulators and fully flush the fluid and probably get back to something that feels pretty new. I'd plan on this no matter the state of the AHC system when you purchase, unless there are very specific receipts showing that it had been done recently. Mileage is probably irrelevant at this point on 2013 and older vehicles as the age of the accumulators will be reason enough to swap them out. If you are not the "fix it in your driveway" type, and are considering an older LX, hopefully you have a good indy mechanic who is willing to learn or already has experience with AHC and land cruisers in general. If not, I'd be shopping for a 2016+ LX/LC.

 

[pvchaitanya]

Thanks for the guidance everyone. I went and checked out my first potential LX yesterday (2013 95K miles). Everything seemed in reasonable condition except the AHC. It wouldn't raise or lower consistently. And when it did, the front would drop and then the back. Is it safe to assume it is supposed to raise and lower evenly? I did pull the reservoir cover and did find that the fluid was below 'low'. This particular LX has had a consistent maintenance history throughout its life at a Lexus dealership, so I was quite surprised. Not being 100% confident yet in my LX diagnostic skills/knowledge, and knowing how complicated/expensive the AHC system is, I passed on the vehicle.

I think you misunderstood how the AHC works. It actually works in stages and back raises first and then front raises to level with the back. Also if you are holding the brake, it would not raise fully. Best is to test it in park with all doors closed.

I would doubt that the AHC fluid is low or bad, in any case, as long as the AHC is moving correctly without any major squeal or squeaks, its easier to flush and replace it with new fluid.

If everything else is good, the AHC as you mentioned is also functioning good.

 

[rustsatz]

Thanks again for all the knowledge and wisdom!

Is this a 'normal' level?

 

[TR4RUNNER]

Thanks again for all the knowledge and wisdom!

Is this a 'normal' level?

View attachment 3113362

Looks like it’s low but not empty. If the truck is in ‘HI’ the fluid should be near the ‘min’ line. Might just need more fluid or have a leak somewhere.

 

[rustsatz]

This LX also had a damaged front park assist camera. The plastic cover protecting the lens was missing and was not functioning on the monitor. Is that an easy item to replace?

 

[lx200inAR]

This LX also had a damaged front park assist camera. The plastic cover protecting the lens was missing and was not functioning on the monitor. Is that an easy item to replace?

Easy yes, cheap no... There have been a few threads around here retrofitting an aftermarket camera, that's cheaper. The difficulty is the factory camera is 6v and not 12v.