LX570 AHC Fault - quick advice needed :) Fuse?

[LXinOBX]

About 80 miles into a 160 mile (one way) ski trip, made a quick bathroom stop, when restarting and pulling back out onto highway, AHC "flashed" moving from low to normal, but before normal mode reached, the display flashed as below and remained in lo (manual switch did nothing, engaged 4WD, icon flashed but 4WD never engaged). After a few more attempts to engage, when starting the engine the display immediately was as below (no graphic indicating moving from lo to normal).

We have a ton of snow and ice so ran the truck through an under carriage wash just in case something was "frozen" ....no change.

Conversation w Lexus said OK to drive (it's actually very manageable - NOTHING like a 100 LX470 when stuck in lo).

Based on the symptoms presented, is there a chance it could be one of the AHC fuses? Where we are situated, it is a total PITA to get to the truck (even to sort the fuses) so before I just run the truck over to the dealer when we get home, is it a possibility a fuse issue (I'm thinking the pump failed).

Many thanks for any advice!

 

[TeCKis300]

It could be anything and would be very hard to diagnose from afar.

Basic checks would be fluid level. Which is not as easy as the 100-series as it's tucked behind a panel in the passenger rear wheel well. Would need a 10mm wrench to open panel. And a flashlight to illuminate the reservoir.

From the 100-series, another common fault for older vehicles is one of the height position sensors potentiometers have failed.

There's not a lot of information on failure modes in these systems as they don't typically fail. More will happen as these cars age. Sorry if you're one of the first that I've seen report an actual AHC CEL.

You won't be able to do much out there anyways as you can't just find AHC fluid. I'd just drive her and enjoy the trip. Sounds like there's still AHC pressure and damping/ride is still good anyways. And ultimately, suspension won't leave you stranded.

 

[LXinOBX]

TeCKis300, thanks for chiming in, really appreciate it. Yeah, remote troubleshooting is always tough! In talking w Lexus and Service we never thought that possibly the level was low - no premature drips or leaks so the chance of a leak is small (nothing on the resort floor) - BUT if it started to leak at the beginning of the trip it may have leaked enough to "fail" at the first park (when the system fully cycled from normal to lo and then upon restart, lo to norm) - I'll definitely take a look.

Regardless, soon as I get it sorted I'll report back.

If anyone else has any ideas, please, let us know your thoughts.

 

[grinchy]

Wow. That is definitely something I hope never to see! Does it lift the vehicle at all, or just 'try' and then error? 4Lo mode may not engage, that is a common issue with the solenoid. Put it in 4Lo then turn off, it should engage on the restart. I had this issue until I put it in 4Lo weekly five or six weeks running.

 

[LXinOBX]

Hey, Grinchy, the vehicle does not lift at all. When the symptom first presented (after stop mentioned above) as we were pulling away the display indicated it was lifting, but I noted it was taking longer than normal, after about a minute the display flashed as above. I pulled over and cycled through engine stop/start, engaging the diff (it just flashed, did not stop until I turn engine off) and manually moving the center console manual raise/lower switch. I even turned off the auto raise lower (little man ducking graphic) - nada.

I'll try the 4lo thing now - you drove in lo (squatted) mode for a sustained period? If so, wow.

Separately, and I'll probably be banned for this, when driving on a smooth road, it's kinda cool being a lo rider - and, on the (only) plus side, at refueling I noted I was at almost 18MPG. Not unusual for all highway driving, but for a tank of gas, where it was well below freezing and driving about 1/4 of that tank on seriously hilly mountain roads I have to think the lower wind profile was really helping on the interstate driving portion at 75/80.

 

[Ali FJ80]

Editing out info on a warning as stated below there is not a specific one and I must have been given bad info. Apologies.

 

[Ali FJ80]

Sorry, double posted and cant seem to delete.

 

[grinchy]

Sorry no I don’t drive in Ahc lo, it will go to Normal at a certain speed I think.

It’s 4lo range i was referring too. Switch the switch to 4lo see errors on dash. Turn off car ( leave the switch in 4lo) . Turn the car on, it should engage.

 

[04UZJ100]

It should be simple enough to remove the one bolt with a pliers if that’s all you have. You can shine a light through the reservoir to verify level.

On each engine start, you should also be able to hear the pump run, even if height was not moved.

Those are two easy things to start with.

 

[LXinOBX]

Just a quick update - AHC line corroded where the lines run laterally; specifically at the mounting bracket point. I guess it held moisture. Apparently Lexus is just starting to see more and more of these ..that location is certainly now on my "hit extra w salt away" and "douse w fluid film" point

 

[04UZJ100]

Thanks for update. Are the lines easily visible from underneath the truck at that location?

 

[LXinOBX]

Yup, but they are really tucked up (brackets are secured to body (vs frame) there. Like an idiot, I didn't take a pic while out under it in the shop. The area, I suspect, really gets stuff (including salt) blasted up there and since it's "protected" doesn't get much air flow to dry it out.

One thing I also learned - there is NO low AHC fluid alert so best to check it (pop the rear "hatch") from time to time.

 

[ImTod]

What age and mileage did this happen to your LX at? You mentioned salt spray, do you think it would also be something to keep an eye on in areas that don't regularly see salt on their roads?

 

[LXinOBX]

What age and mileage did this happen to your LX at? You mentioned salt spray, do you think it would also be something to keep an eye on in areas that don't regularly see salt on their roads?

Dunno (LX is a '10 w 140k). All I can say is that the dealer I use this time of year (Sheehy - Annapolis Md - a platinum dealer) said, they have seen about 9 or 10 of these instances (only this particular line) so far.

I see you are Alabama - if coastal, I'd watch (and de salt and FF) the area like a banshee. That environment makes salt on the road child's play.

It ought not to happen - didn't Toyota learn anything with the rear AC line on the 100 LX?

I did notice on a '19 LX in the showroom that the undercoating is almost waxy (close to the asphalt/tar we used to shoot on the underside of our 40's and 60's back in the day) - I don't recall the original undercoating to be like that.

 

[Chocolate]

This happened to me in November also at ~52k miles. Mine is a 2013 and I have been proactive about washing salt away, but as you said, there's places that are difficult to reach. The good thing is I got a brand new line and new AHC fluid put in (total cost: 1000 dollars), for free. Unfortunately, the L/Certification on mine goes away next month. Glad it happened under warranty.

While this corrosion happens on the outside, after 5 or more years, I believe changing all of the factory fluids is beneficial. Power steering fluid, brake fluid, suspension fluid, differential oils, transmission fluid, become less effective and sometimes more corrosive over time.

It seems to affect us in the winter climates a lot more, because there are 08/09 LXs with well over 100k in areas without road salt that do not seem to have this issue.

 

[LXinOBX]

It seems to affect us in the winter climates a lot more, because there are 08/09 LXs with well over 100k in areas without road salt that do not seem to have this issue.

Wow, 52k and only 5 years young! That is really disappointing. I'm curious, did your issue present itself where the line runs laterally? I do wonder if this is becoming more prevalent, but not yet a TSB. I appealed to Lexus care was shot down and zero consideration offered - and the senior team member I spoke w seemed very scripted on the subject.

Surprisingly, it's not only winter/salt, that contributes it is also "salt air" of coastal regions - where no road salt is even needed in winters or used. At least in the winter it's cold, slowing the "rust" process - the process goes on steroids when the salt is in the air, humidity is 90% and it's 85 out.

 

[luke27617]

One system that scared me and pushed me to by LC even though would prefer LX for interior comforts.

 

[Chocolate]

Well, you have to expect having a sophisticated suspension that it will require more maintenance than a coilover system. However, the LX has adjustable height suspension from the factory. If you go the LC route with an aftermarket suspension, which costs thousands of dollars to match or exceed the ground clearance of the LX, rebuilds can be a factor at 60-80,000 miles.

I'll also be going with LT285/70/17 for my next set (after much back and forth vs 285/75/17) because the vehicle is still driveable for some time without all the fluid in the system on 33s (among other reasons, the bigger reason being the wheel wells are just too damn small in general). On 34s, you would start rubbing very quickly. Then there are heavily loaded or towing situations. I really like the additional sidewall, but the rubbing concerns are not worth the extra 0.3" (7.62mm) of sidewall, for me. I would feel more comfortable running a 34 with a permanent 2 inch lift.

The part that needed to be replaced is 48999-60010, which actually only retails for about 60 bucks. It is the line nearest the height control motor. AHC fluid is about $15 a quart, so most of the warranty cost was in labor.

 

[LXinOBX]

For the benefit of the forum, in addition to the 48999-600010, mentioned above by Chocolate - also corroded and replaced on our LX was 48998-60010.

 

[04UZJ100]

When replacing the lines, the system is self bleeding I assume at the bleed locations in each corner?