New to forum. Just bought 2003LX - hope not a mistake. Have an AHC question already.

[tbuck]

Been looking for Gray 2003 LC or LX for a while. With no luck local, I find a pretty good deal on-line, fly in to drive it home. Didn't (and don't) know much about the AHC system, dealer said it didn't work which was okay with me as it's not a feature I plan to use. While I was on the lot, I pushed the button several times with no response so I assumed the dealer was correct. Can't say for sure I was doing everything just right to engage the system while I was on the lot (push brake, don't push brake .... not sure).

Everything is fine as I'm driving the 1,00 mile trip home, AHC indicator shows N and the ride is very smooth. I'm in and out of the truck numerous times for stops over 2 days and all is okay .... until the last stop for gas. When I get back in the truck and start it up, the front end lowers, the AHC indicator goes to L and the OFF light begins to blink. The last 50 miles is like I'm riding a goat.

It now is low in the front (really low) and doesn't respond to AHC button.

I've done a fair amount of searching on the forum and understand it could be a sensor or worse, the pump. Fluid level is high. I've ordered a mini VCI TIS cable as suggested throughout the forum and will give it a go.

So my question ..... what data/values do I look for to determine the issue once I get it hooked up? Will it point the finger at the specific sensor and/or the pump? Any suggestions on troubleshooting are appreciated.

Man, I hope this doesn't turn out to be a mistake.

 

[ryanCA]

I don't know if your ride quality got stiff because of the pump (definitely possible) or if the Actuator speres went bad (common)... but the blinking 'OFF' light, spinning motor, no response, high fluid tank level, no fluid movement, and abnormal fluid pressure (too low?) would in my opinion, indicate your pump went bad... and aparently, they do. This part is much cheaper than actuators, shocks, etc, and if you got some high miles, or used the AHC a lot, then I'd definitely recommend changing it.

 

[Slickspawn]

Stuff happens. Can you install a pump yourself? You will love the 100 series.
No regrets.

Put it this way I have had Jeeps, 4Runners, Dodge Cummins (multiple), garbage F350/250s, Silverados and finally a Land Cruiser. Cruiser is my favorite. Ever.

 

[TXLX100]

If you plan to keep it for anytime, it be worth your while to diagnose it. If the torsion bars / springs are week could be causing high pressure in the system which would shut it off. In would start with checking pressure with a toyota scan tool, bleed the system, adjust the torsion bars and replace the rear springs if it shows high pressure. There is a module in the tech stream software for the system, it will show front and rear pressures. Generally, I think you want to be around 5 or 6 on the pressure. It will go up and down when the vehicle is raising or lowering. Pumps dnt fail a lot, but are somewhat easy to change. You can probably get a working junkyard unit if you are on a budget.

 

[PADDO]

What you have described is a failed or loose front height sensor, the system has gone into fail safe and the fluid level is high because your front end is in low (the fluid that was in the front actuators holding the front at N height is now in the reservoir) and you're possibly on the bumps. Your pump is most likely fine, they last forever. You can check the height sensor lever mechanisms for security and manually check the rheostats are working with a battery and multimeter. Taking height sensors apart to clean them and hopefully return them to service is an easy job too.
You can also manually extract dtc that may implicate a defective height sensor or low pump output pressure and also manually drive the pump and individually raise or lower the front or rear. But with the front slumped to low this has nothing to do with a failed pump or globe accumulator, as these accumulators affect ride quality (damping) not height. I've previously posted the fsm procedures to do these tasks so do a quick search under posts by me and you should be able to find the PDFs. If you can't then pm me and I'll email them to you and talk you through what needs to be done to sort this out

 

[tbuck]

Thanks for the quick feedback from all. It definitely feels (and looks) like it is on the bumps. I hope PADDO is right and pulling and cleaning the sensors will get it back on the road. I'll be searching for those PDF's mentioned .... and thanks for the offer of additional help.

I'll let you know what I find.

Looking forward to this first project on this truck which I plan to keep for many years - only 120k on the clock.

 

[Traskew3]

Rip it off and put a lift on it!! That's what Im gonna do when it goes out

 

[Sandroad]

An '03 with only 120K is a good find. With this crew riding shotgun, you'll get the suspension sorted and be running smooth soon.

 

[tbuck]

As PADDO suggested, it seems to be a sensor. The passenger side sensor is corroded beyond repair .... the springs pretty much disintegrated. The driver side sensor, surprisingly enough, is in good shape.

While I'm waiting on a new sensor to arrive, is there anyway to override them and get the truck back to the Normal position so I can drive it? I got the VCI TIS cable in today.

 

[PADDO]

This procedure is worth a shot, with sensors disconnected and the system in fail safe your options are limited but you might be able to override the ecu and get the front to raise. The sst can be as simple as a paper clip.

 

[PADDO]

Here is another version of manually raising/lowering. DLC1 (passenger side under the hood) is easier to access.

 

[tbuck]

I tried the DLC1 option with no luck. I assume that the sensors are to be disconnected and even further I did not reinstall the bad sensor sub assy should that matter.

Where do I find the DLC3 box to give that one a go?

 

[Rando Kuruza]

Got a qoute to rip out ahc put in a 1.5 inch lift for 1,700 bucks do that instead...

 

[PADDO]

I tried the DLC1 option with no luck. I assume that the sensors are to be disconnected and even further I did not reinstall the bad sensor sub assy should that matter.

Where do I find the DLC3 box to give that one a go?

DLC3 is the obd2 connector in the drivers side footwell.

 

[tbuck]

Thanks, paddo.

No luck with DLC3 either. But, for what it's worth, it doesn't look like the Ts port has a connector in it (am I'm sure I was looking at it the right way as compared to the diagram). So where I can see metal receivers in many of the DLC3 ports, the Ts port appears blank - like it is unused. There was no response on the dash.

When I tried the jumper in DLC3 last night, the OFF button immediately began the quicker flashing (didn't have to push the DOWN button 5 times) but I got no response with the UP button.

Couple of questions:

1. Does connection thru the VCI TIS cable provide access the height control system?
2. What have you found to be the best on-line source for parts for these trucks?

 

[PADDO]

I'll check out Ts on dlc3. I prefer using dlc1 because it's so much more convenient than dlc3.
To your Qs. Yes techstream enables you to access the ahc ecu and conduct tests under the utility function and most importantly it lets you view the front and rear pressures (momentary outputs from the pump when raised from L to N) and sensor height values whilst in the data list function. There are many techstream screen shots in the behemoth "definitive list of ahc maintenance items" that will give you an idea. Start at the last post and work backward unless you feel like wading through 12 or 13 pages!
I recommend Google for the part # you're after to compare prices and S&H. The supporting Toyota part vendors on here should be able to help with AHC parts as there is commonality for LC MY '06 and '07. Often they (Mud Toyota parts guys) can't help with Lexus specific parts as they aren't within their brand network but they should be good here. I quick google for a height sensor assembly shows prices as low as $235 with $280 being the norm.

 

[Jutt]

Man, I hope this doesn't turn out to be a mistake.

We just recently purchased a LX. I would have preferred a LC without AHC but we found a good deal on a LX and the AHC works but I was fully prepared to buy a LX with a non-working AHC system and convert it to a standard suspension because the overall vehicle makes it worthwhile.

Best case scenario, you can fix the AHC without much money or time. Worse case, delete AHC, install an OME setup and never have to worry about AHC again. No mistakes either way IMO unless AHC was a deal breaker.

 

[tbuck]

Amen, jutt. That's exactly where I was; looking for a LC, found a lower mileage LX at a good price ... except unlike you, I didn't know much (anything) about the AHC option on the LX. I hope with help from forum folks like PADDO (and with limited $$) I can get the AHC working. Got a new sensor ordered which I hope does the trick. I'm not ruling out bailing on the AHC as you and others have suggested but I'll give it the ol' college try first.

At this point, I just want to be able to drive the truck.

 

[tbuck]

I got the Techstream up and running so an update on that.

Bought the mini vci toyota tis techstream v10.10.018 from Amazon, sold by YuBest, $28. The CD provided is loaded with 4 different versions of the software, 7 thru 10. I loaded v10 on an XP laptop, followed the directions from a video on YouTube and it's pretty much plug and play. There is no need to hack a dll as was required in earlier versions. I had the truck running when I connected the software and it automatically populated the model code.

With that done, I saw trouble codes from the AHC ECU. I don't remember the numbers (it was late) but as I recall it was irregular pump pressure and wheel speed sensor.

I've read the definitive AHC maintenance post and poked around the Testing and Utility screens and if there is a way to override the failsafe low position and raise the front thru techstream, it isn't intuitive. Any suggestions?

 

[PADDO]

With a height sensor disconnected you're not getting a valid input to one or the other ecu terminals SHFL or SHFR and without that input it's doing what it's suppose to do - prohibit automatic leveling and height adjustments. I'm not aware that this can be overridden in techstream and it seemingly can't be overridden manually by shorting data link terminals. Sooo, until you get the replacement sensor installed I can't see why jumping terminals SHFL and SHFR wouldn't trick the system - just parallel the valid signal from the good sensor onto the terminal without a signal. It really is a pretty basic system, but it just needs valid signals, and for the SH terminals that's between 0.2v and 4.5v with about 2.25v being the null at N height iirc.