AHC Woes: 2013 LX (1 Viewer)

[jjhancock]

Chapter 1:

In October of 2021, I was due for my 60k service and an oil change. Turns out, the AHC should be serviced at this time. I called the Lexus dealership to schedule, and just so happened to have the head of the service department on the phone. I asked him point blank "Are you comfortable doing an AHC flush?" "Sure, we've done thousands of them..." I asked again "Are you 100% confident that your service department can do this? There are horror stories out there of this procedure being botched..." "Yes, we are 100% confident in this. The system is bulletproof, and you really can't screw it up." I proceeded to schedule the appointment.

On the day that I dropped the LX off, I again asked the guy who was taking the vehicle in "Are you 100% confident that your service department knows how to properly to this AHC service?" "Oh yeah, we do this all the time. It's really quick and easy, and the system is literally bulletproof. You really can't mess it up!"

Later that day they call me to tell me the truck is ready to pick up. I drive the 20 miles back to the dealership, drop off the loaner, throw down the AMEX, and get my keys back. I walk out to the parking lot where my truck is sitting, get in, and fire it up. She starts right up, is in Neutral mode, and there are no warning lights on the dash. After letting it warm up for a minute, I flick the switch to go to High mode. It tries for about 3 seconds, then the AHC warning message comes up and it drops back to neutral. I drop it to Low mode, and it goes. Then back up to Neutral, and it tries, and fails.

I'm still in the parking lot at this point, so I go back in as they are locking the place up, and I tell the service guy what's going on. He comes out to check the situation, and agrees that it isn't right. I get a new loaner and go home, in quite the mood.

The next day the service department manager calls me and says "well, this pump must have been on it's way out when you dropped it off. Did it ever work?" I politely told him that it had never NOT worked impeccably, and that he had personally assured me that the system was bulletproof and you really can't mess up the job.

After two weeks, they ended up covering the cost of the AHC pump that they fried, as well as the labor, and they made it right. The AHC then worked great for the next 13 months.

 

[jjhancock]

Chapter 2:

Two weeks ago I get in the LX, fire it up, and the dashboard blows up like a Christmas tree. It's running, but the CEL is on, and the 4Lo light is blinking. I pop the hood, and there has clearly been a rodent in there. I suspect the little furry devil chewed on the wiring harness. Merry Christmas to me!!

I take it to the same Lexus dealership again, and they confirm that the wiring harness is toast, there is rodent damage, and I need a new wiring harness, and they can't get the new wiring harness in for a week. $1308.00 later, I pick up the truck, and it is apparently fixed and working properly. Sweet! Now I can move on with my life and head out of town for the weekend.

I drove to Vail with my dog and girlfriend on New Years Eve. The LX ran great. I'm a proud owner once again.

The next morning I started the truck like normal, in 30 degree temps, and she fires right up. 30 seconds later, the "Check 4-Wheel AHC System" message comes up on the display out of nowhere.

I continued to drive for the rest of the weekend without issue, but I didn't mess with anything at all (there was feet of snow and I had no garage to even begin to assess what the issue was). We drove home after the New Year with the truck in Neutral mode, and all was just fine, although I felt like the handling wasn't as good as it was prior to the warning message displaying (maybe I was being paranoid, not sure).

Now that I am home, I tested the AHC system in my driveway, and it doesn't work AT ALL. The ride is horrible, and the warning light is still on. It's still in Neutral mode, thankfully.

Tomorrow morning I am scheduled to drive the 20 miles back to the dealership for them to assess the situation.

What I'm wondering is whether or not I should have the LX towed on a flat bed, or if I should drive it there? Am I likely to cause more damage by driving it carefully the 20 miles? Has anyone experienced a failure like this out of the blue when the AHC system hasn't been touched in 13 months?

Thanks in advance for any words of wisdom. This truly is a spectacular community, and I'm grateful for you all!

 

[tbisaacs]

Sounds like a pain. Have you tried pulling the code? And possibly considering another dealer or an independent Japanese shop?

 

[32cls6speedmt]

There was a member o here who posted that Lexus Colorado Springs knows the lx. He gets service there.

I am going to guess and speculate that might have used the old plastic bottles of ahc fluid. Possible burned out the second pump over time. Just a guess.

 

[Nothinghead]

There was a member o here who posted that Lexus Colorado Springs knows the lx. He gets service there.

I am going to guess and speculate that might have used the old plastic bottles of ahc fluid. Possible burned out the second pump over time. Just a guess.

What’s the issue with plastic AHC fluid bottles?

Reading about hydraulic failure on new years makes me wonder about water freezing in the system. I have no idea of AHC fluid is hygroscopic.

 

[jjhancock]

Sounds like a pain. Have you tried pulling the code? And possibly considering another dealer or an independent Japanese shop?

I ordered the code reader last night, the Veepeak, but it won't be here for a few more days. I may grab the ScanGuage II out of my 80 series tonight and see what I can find.

Robbie Antonson is in my neck of the woods, and he's really the person I trust most to work on my trucks. There are some other highly regarded independent shops in town, including Slee, whom I could reach out to. I guess part of my hope with going to the dealer is that they last touched my truck, they replaced the AHC pump 13 months ago, and if they screwed something up, maybe they will make good on it like when they botched the AHC flush. But the warranty on the AHC pump replacement and labor is stated to only be good for 12 months.

Honestly, I have had the LX for 3 years now, and it's bone stock. In just the last couple months I have been spending time in the 200 series forum trying to learn my way around it and understand all of it's quirks before I start turning wrenches on it. I'm in the planning phase of my build, with a set of nearly mint Rock Warriors boxed in my basement, my tire choice mostly made, and am almost set on a rack and front bumper.

So this is disheartening and is likely going to put a pause on my build for a bit.

 

[jjhancock]

There was a member o here who posted that Lexus Colorado Springs knows the lx. He gets service there.

I am going to guess and speculate that might have used the old plastic bottles of ahc fluid. Possible burned out the second pump over time. Just a guess.

I read that about the Colorado Springs Lexus dealer as well. I have them in mind, but it's a bit of a haul to get to them from Boulder.

 

[jjhancock]

What’s the issue with plastic AHC fluid bottles?

Reading about hydraulic failure on new years makes me wonder about water freezing in the system. I have no idea of AHC fluid is hygroscopic.

There was at least 1 bad batch of the AHC fluid, and I believe that they were the 1L sized plastic bottles. There is something about there being some coagulating or it getting sludgy in the bottles, which in turn keeps the system from pumping fluid the way it is intended to. I believe it is well known but that Toyota / Lexus isn't exactly fessing up to their screw up and the chaos that that batch has caused.

I have read, however, that several members on Mud have been able to re-flush the system with the good AHC fluid once they were able to figure out the issue and get their hands on the good stuff.

As far as the freezing goes, I thought about that as well. Or maybe even a frozen globe or actuator of some sort. The reason that I have mostly dismissed that, is that the day I drove in to the dealership to get the wiring harness repaired, it was -16 degrees outside, and stayed sub zero for several days, and I didn't get any warnings.

Additionally, the system is stated to function down to -36 degrees by design, and some far north members have confirmed that the system does in fact function at -30 something degrees.

 

[1world1love]

Don't discount the possibility that the rodent damage was more extensive than originally assessed. They may have chewed a wire that then corroded over time and now is faulty. I don't think any of the hydraulic lines are susceptible, but I once had a rat "borrow" a piece of hose from my wiper fluid system in a different vehicle and a friend had a brake line that had a hole chewed in it.

I just had $4k damage repaired on my Highlander, including several wires and a piece of hose attached to the evap canister.

 

[jjhancock]

Don't discount the possibility that the rodent damage was more extensive than originally assessed. They may have chewed a wire that then corroded over time and now is faulty. I don't think any of the hydraulic lines are susceptible, but I once had a rat "borrow" a piece of hose from my wiper fluid system in a different vehicle and a friend had a brake line that had a hole chewed in it.

I just had $4k damage repaired on my Highlander, including several wires and a piece of hose attached to the evap canister.

Funny you mention this, as I'm starting to believe that it was the rat again...

 

[jjhancock]

Update:

I got the ScanGuage II out of my 80 series and plugged it into the LX. It said there are no codes. Seems crazy considering there is an AHC warning on the dash.

So I ran to the local auto parts store, thinking maybe my old ScanGuage II couldn't read from a newer vehicle. The guy plugged in his scanner, and same result... no codes.

My bet is that this rodent got back in there and chewed something else. I put a bar of Irish Spring under the hood as a deterrent the other day, and I also set two more rat traps and put them under the LX just now.

I did kill a tree rat in a trap in my driveway two nights after I took the LX in to get the wiring harness replaced last time...

Who knows, maybe the rat I killed isn't the rat bastard who did the damage last time around.

Besides a bar of Irish Spring under the hood (I was advised to do this by the Lexus dealership), and setting traps of course, does anybody have any sage advice to keeping rodents away from my truck? Unfortunately, I do NOT have a garage to park it in. I also don't want to put poison out as there are some free roaming neighbor cats in the neighborhood, and I would hate to inadvertently kill one of them (although they certainly aren't doing their job very well at the moment).

 

[slipkid13]

There was a member o here who posted that Lexus Colorado Springs knows the lx. He gets service there.

I am going to guess and speculate that might have used the old plastic bottles of ahc fluid. Possible burned out the second pump over time. Just a guess.

That's me. I had them service it at 60K and they just recently replaced a leaking line in the AHC system and did a flush. No issues. I am also driving a 2013 LX

 

[slipkid13]

Update:

I got the ScanGuage II out of my 80 series and plugged it into the LX. It said there are no codes. Seems crazy considering there is an AHC warning on the dash.

So I ran to the local auto parts store, thinking maybe my old ScanGuage II couldn't read from a newer vehicle. The guy plugged in his scanner, and same result... no codes.

My bet is that this rodent got back in there and chewed something else. I put a bar of Irish Spring under the hood as a deterrent the other day, and I also set two more rat traps and put them under the LX just now.

I did kill a tree rat in a trap in my driveway two nights after I took the LX in to get the wiring harness replaced last time...

Who knows, maybe the rat I killed isn't the rat bastard who did the damage last time around.

Besides a bar of Irish Spring under the hood (I was advised to do this by the Lexus dealership), and setting traps of course, does anybody have any sage advice to keeping rodents away from my truck? Unfortunately, I do NOT have a garage to park it in. I also don't want to put poison out as there are some free roaming neighbor cats in the neighborhood, and I would hate to inadvertently kill one of them (although they certainly aren't doing their job very well at the moment).

Can you place some poison in the engine compartment, where the cats are not likely to go but rats will?

 

[jjhancock]

Can you place some poison in the engine compartment, where the cats are not likely to go but rats will?

I suppose I could do that. My only fear about rat poison is that they usually go someplace and die and the corpse rots someplace that you can’t find them. That’s why I went with traps baited with peanut butter.

 

[jjhancock]

Here’s the one I got last week.

 

[grinchy]

There is an ahc connector on the inside of the frame rail, just opposite the bracket. I’d check that it is fully plugged in and not chewed. I have a pic of it somewhere, and I can confirm the error you see. However I did have codes, thought some code readers can’t see all codes, I was using techstream.

<edit pics in this post
Post in thread 'Factory sub tank - sourcing and fitment discussion'
Factory sub tank - sourcing and fitment discussion - https://forum.ih8mud.com/threads/factory-sub-tank-sourcing-and-fitment-discussion.1239785/post-13730032>

 

[jjhancock]

There is an ahc connector on the inside of the frame rail, just opposite the bracket. I’d check that it is fully plugged in and not chewed. I have a pic of it somewhere, and I can confirm the error you see. However I did have codes, thought some code readers can’t see all codes, I was using techstream.

<edit pics in this post
Post in thread 'Factory sub tank - sourcing and fitment discussion'
Factory sub tank - sourcing and fitment discussion - https://forum.ih8mud.com/threads/factory-sub-tank-sourcing-and-fitment-discussion.1239785/post-13730032>

Thanks @grinchy much appreciated!!

Thanks for taking the time to link to the post with the photo of the AHC connector!

 

[CanadianRockyCruiser]

There is an ahc connector on the inside of the frame rail, just opposite the bracket. I’d check that it is fully plugged in and not chewed. I have a pic of it somewhere, and I can confirm the error you see. However I did have codes, thought some code readers can’t see all codes, I was using techstream.

<edit pics in this post
Post in thread 'Factory sub tank - sourcing and fitment discussion'
Factory sub tank - sourcing and fitment discussion - https://forum.ih8mud.com/threads/factory-sub-tank-sourcing-and-fitment-discussion.1239785/post-13730032>

Where on earth did you source that color wiring harness diagram?

 

[grinchy]

It’s one of the electrical items included in the fsm web package. It has every wire bundle and connector shape in it.

Thread 'DIY your own FSM'
DIY your own FSM - https://forum.ih8mud.com/threads/diy-your-own-fsm.1272641/

 

[lx200inAR]

For tshooting AHC, best to have Techstream rather than a code reader. You should have Veepeak as well.. but Techstream will get you DYCs that ge Eric OBDII scanners wont get. Im not sure if OBD Fusion with the Toyota pack will get AHC DTCs but it definitely can read data from the AHC ECU.

I suspect the ride is rough because the dynamic valving (AVS) is probably disabled..