Check 4-Wheel AHC System - Displayed Once, Now Cleared

[Chaldaean]

I fired up the truck in 30F weather and the "Check 4-Wheel AHC System" warning displayed.

The warning has not re-appeared after multiple subsequent starts.

I'm hesitant to ask this question as there may be too many possibilities, but is there a "common" thing I should check?

At this point, would a fluid flush be a good move or could that be a potential waste if I need to open the system up for component replacement?

Reading a bunch of threads, I just ordered a Techstream cable.

 

[hickuptruck]

might be a sensor froze with ice?

 

[g1701gst]

The first thing to check is your AHC fluid level in the rear passenger wheel well. Just one 10mm bolt to remove the access cover. The level can be hard to see but holding a flashlight to the tank from above or behind can help. If you don't know when the last time the fluid was flushed, I'd recommend a flush.

 

[Chaldaean]

might be a sensor froze with ice?

Do you mean a ride height sensor or something else? Thanks for the reply.

The first thing to check is your AHC fluid level in the rear passenger wheel well. Just one 10mm bolt to remove the access cover. The level can be hard to see but holding a flashlight to the tank from above or behind can help. If you don't know when the last time the fluid was flushed, I'd recommend a flush.

Fluid level checked okay (at max fill line), so I'll do a flush. Thanks for the advice.

 

[Aint Misbehavin]

Resurrecting an old thread. I’m up in Moab right now and am getting this fault. I changed my fluid last spring and it was clean. Have y’all noticed these faults in cold weather? When I go to high mode the pump does sound like it’s struggling.

 

[CharlieS]

Okay, so maybe not helpful, but my hydraulic car lifts strain at the top when they are a bit low on fluid. Seems like the AHC is a similar *type* of system. How're your fluid levels?

 

[supercarrera]

How old are your tire pressure sensors? It's possible the cold climate you're in has pushed one of your sensor batteries over the edge and it finally died.

 

[Aint Misbehavin]

Thanks for the replies. Tire senders are one year old. I will check the AHC fluid level tomorrow.

 

[ERC4]

Do you mean a ride height sensor or something else? Thanks for the reply.



Fluid level checked okay (at max fill line), so I'll do a flush. Thanks for the advice.

What was the ultimate outcome of this AHC warning light for you? I got one briefly today on a 2013 LX with 88k miles on it. It can't be weather related as it was 73 degrees in San Diego today.

 

[Aint Misbehavin]

For mine I was a little low on fluid. I had raised my rear height sensors and I think that triggered the fault. After adding fluid I haven’t had any issues.

 

[lx200inAR]

Tech stream should have a stored fault if you check that. Also, having read up a bit on it (I was getting check light periodically due to low fluid), the system has many checks and errors on the side of caution. Almost every thing in the manual that has anything to do with AHC says to restart the truck and if the failure goes away you are probably good. That’s assuming you can go through all the modes without triggering again. A slightly low fluid condition generally won’t trigger an alert until you lift into high mode, and possibly extra high mode. Try using crawl control (to get to AHC highest setting) for a bit and see if you can drive a bit without it triggering.

 

[Chaldaean]

What was the ultimate outcome of this AHC warning light for you? I got one briefly today on a 2013 LX with 88k miles on it. It can't be weather related as it was 73 degrees in San Diego today.

It only showed up once and never re-appeared.

I bought the new fluid, a fluid pump and the Techstream. They have all been sitting in my garage. I probably just jinxed it!

 

[lx200inAR]

If you don't think it's ever been flushed, it's worth spending an hour doing it. Mine was low on fluid and old at 100k miles when I purchased. I did a flush and proper fill and my system went from triggering alerts randomly and being slow to raise to now it runs great. Haven't had any failure triggers since and goes up and down in time FSM alots for each procedure. The fluid in my system was almost black.

Also, good to check the fluid level yourself. I took mine to my local, usually trusted mechanic after the Check AHC light triggered a few times with the direction of specifically checking the AHC system and completing a "flush/fill and bleed." He ended up not charging me and giving it back saying they "did it all and it looked great". I was still getting errors after getting it back and also assumed there was no way he did a fluid flush since that would have cost him at minimum $75 in parts, so checked it myself. My fluid was so low you could barely tell there was any in the reservoir. Probably at best they bled the system and never checked the reservoir for fluid level. I suspect I'm lucky they didn't bleed it enough to completely run the pump dry.

 

[ERC4]

Misbehavin, LX200 and Chal, thanks for your responses. Very helpful. Appreciate it.

 

[gplin96]

What is the name of the fluid and where is the reservoir? Can I buy the fluid at an auto parts store. I want start from there. I have the dashboard warning to check 4 wheel AHC system. Truck is in the lowest setting and won’t move up from there. No codes come up On a cheap OBD Reader. Thanks!

 

[AnyMal]

What is the name of the fluid and where is the reservoir? Can I buy the fluid at an auto parts store. I want start from there. I have the dashboard warning to check 4 wheel AHC system. Truck is in the lowest setting and won’t move up from there. No codes come up On a cheap OBD Reader. Thanks!

Suspension fluid. 08886-81221
Make sure to check the fluid for debris!


Super easy to do tons of tutorials on mud to search and a bad fluid thread on the front page still.

 

[lx200inAR]

What is the name of the fluid and where is the reservoir? Can I buy the fluid at an auto parts store. I want start from there. I have the dashboard warning to check 4 wheel AHC system. Truck is in the lowest setting and won’t move up from there. No codes come up On a cheap OBD Reader. Thanks!

You’ll need Texhstream for codes.

 

[gplin96]

I would like to bounce something off of you guys. If my 570 lost most of the hydraulic fluid from a leak, (that’s what Toyota says) and I want to get my vehicle up from the lowest setting to a more drivable setting, could I fill up the reservoir and will the vehicle stay up or eventually drop down? Thanks!

 

[AnyMal]

I would like to bounce something off of you guys. If my 570 lost most of the hydraulic fluid from a leak, (that’s what Toyota says) and I want to get my vehicle up from the lowest setting to a more drivable setting, could I fill up the reservoir and will the vehicle stay up or eventually drop down? Thanks!

Sorry to hear about that. It depends on where the leak is. If it’s the reservoir it won’t affect anything once it’s lifted back up. If it’s further down the line could be a huge mess or even a larger rupture.

 

[lx200inAR]

if the leak hasnt been resolved, probably not. It would have to be a very slow leak. If leak is before leveling valves, you’ll never get it to raise, and if it’s after, it might raise, but most likely only for a short period.

Did they say where it was leaking from?

Also at this point you probably have air in the system, so once leak is resolved you’ll need to bleed system.