Quick question about AHC ride with extra weight (1 Viewer)

[ParaJake]

Hey guys, I have a 2006 land cruiser and I like the ride on it for the most part but I feel I may be missing out on something due to having AHC problems. Everyone says the land cruisers ride like clouds, but its not all THAT smooth to me. It rides pretty good, but only slightly better than my 2003 stock 4runner that I traded for this 100 series.
My 100 won't drop to low or lift up to high. This isn't a huge issue to me if its not causing any deficit in the ride. But, I had never ridden in a land cruiser prior to buying this one and I have never ridden in any other land cruiser so I don't have anything to compare it to.

After starting my car and driving for a few seconds, the AHC OFF light flashes constantly. I had this checked by a Toyota dealership and they said it was all of the height sensors. Does this sound right? That ALL of the sensors are bad? Or is it a fluke?

I'd love to get this thing working 100%, but I can deal with non-working AHC for now.

My main question is about riding with passengers in the 2nd row seats. When I have passengers in the second row, the ride gets very bad and I feel bad for the people in the back. It feels like the suspension is bottoming out with no more than 500 lbs in the back seat. This can't be right as I know the towing capacity is way more than that and I know that this thing is rated for more than just a measly 500lbs of human flesh bags in the back. Its actually more like 400lbs. Could this rough ride be due to a failing AHC system? It doesn't ride bad with myself and another in the front seats.

Also, does the ride stiffness control knob (next to the AHC position button) work if the AHC height sensors are bad?

I'd like to mention also that my AHC height control has never worked since I bought this about 7 months ago.

 

[ParaJake]

Ok. Measured the heights and did a quick live time drive data test.

Current fender to hub heights:
FL - 18¾ FR - 18⅞
RL - 19½ RR - 20

Going off of the numbers mentioned in the previous post, these are all low.

Checking the front and rear wheel step: they do, in fact, change while I'm driving. So I think that means the damping is working.

IG Power Source Voltage stays around 12.7 while driving.

+B Power Source Voltage stays around 1.5 while driving.

Heights control sensors were updating live and changing while driving.

Number of Trouble Codes remains at 0.

The oil temp sensor is reading 104F currently.

Steering angle is around -30 while driving straight.

Picture taken after test drive. Vehicle OFF, ignition ON

 

[ParaJake]

I'd like to add that I've never had the ability to monitor things in a vehicle like this live. TechStream is awesome!

 

[ParaJake]

Ok, so the next thing for me to try would be cross leveling correct? Seeing as the as found heights of the vehicle are close physically, does that mean I adjust the actual sensors? Does adjusting torsion bars effect height or just pressure? I thought I saw that on the YotaMD video.

I also realize that the +B voltage is low. I'm not sure how or where to check this at. I have the tools to check it, but I don't know what I'm actually checking.

 

[suprarx7nut]

Your voltages are both low. Was the car running when you took this screenshot? Voltages should both be similar and around 13.5-14+ V. You might have a funky sensor (or three), but that voltage problem is a bit of a non-starter.

Does the car run correctly aside from the AHC problem? Any other faults to speak of? That will help determine if you have a vehicle wide voltage problem, or something specific to the AHC system.

 

[ParaJake]

That screenshot was taken after the drive with the car off, ignition on. The voltages of those 2 systems were similar while driving. I have no other issues to speak of other than a tire pressure sensor light. Which actually recently is no longer lit. Everything, aside from AHC is working as it should.

 

[ramangain]

With rig in P and running and all doors closed, when you hit the up or down AHC lever, can you hear any whirring, like a pump operating? If you do this and wait a minute, does the fluid level in the reservoir change afterwards?

Trying to help you determine if the AHC motor/pump are working, or not.

Also, after you press the lever in the up direction, your pressure sensor values should go non-zero and update at maybe 1-3Hz when connected via Techstream.

 

[ParaJake]

No sound of any kind coming from the pump/motor/reservoir area. When parked, and pushing the up or down switch, the indicator light flashes repeatedly but nothing happens. It will keep flashing unless I select neutral again, in which case it stops.

What do you mean by lever? The arm on the height sensor?

 

[ramangain]

Lever=switch in my previous posts, sorry.

Seems like next up is figuring out why your AHC motor ain't got no juice

 

[suprarx7nut]

No sound of any kind coming from the pump/motor/reservoir area. When parked, and pushing the up or down switch, the indicator light flashes repeatedly but nothing happens. It will keep flashing unless I select neutral again, in which case it stops.

What do you mean by lever? The arm on the height sensor?

I'm very surprised you don't get a fault code if the pump doesn't run.

I'd check for voltage at the pump connector and go from there. The pump should run. If it doesn't, there's typically a fault code.

To ask the dumb question... are you sure you have all the AHC components? Can you share pictures of the AHC pump area and the front and rear shocks?

 

[ParaJake]

I was not able to hear any noises coming from the reservoir area. It was relatively quiet I think. Is the pump supposed to be loud? Will I hear it over a running engine next to my head? I can send pictures of the components in a few minutes.

 

[ParaJake]

Here are the pics requested. Pics of the shocks go FL, FR, RL, RR

 

[uHu]

You have 1.9 inch difference between front sensors. Adjust that to zero (under 0.5") on the sensor linkage, after adjusting left/tight lean to zero by tightening the torsion bar on the lower side. When the difference between the fronts is constantly too big, the ahc goes into "limp mode". This might be the fix you need to get the system to play with you, so that you can measure pressures and globe status.

 

[ParaJake]

@uHu
So to adjust this difference, I'm using the linkage on the height sensors? Should I adjust with the side that's higher? Or the side thats lower? Or, should I do them both equally until they're about the same measurement? I'm a little confused. In your reply, you said use the linkage and the torsion bars?

 

[IndroCruise]

Ok. Measured the heights and did a quick live time drive data test.

Current fender to hub heights:
FL - 18¾ FR - 18⅞
RL - 19½ RR - 20

Going off of the numbers mentioned in the previous post, these are all low.

Checking the front and rear wheel step: they do, in fact, change while I'm driving. So I think that means the damping is working.

IG Power Source Voltage stays around 12.7 while driving.

+B Power Source Voltage stays around 1.5 while driving.

Heights control sensors were updating live and changing while driving.

Number of Trouble Codes remains at 0.

The oil temp sensor is reading 104F currently.

Steering angle is around -30 while driving straight.

Picture taken after test drive. Vehicle OFF, ignition ON

View attachment 2734476

Hub-to-fender heights show that the vehicle physically is cross-level at the front -- difference is 1/8th inch and well within tolerance as described in relevant attachment at Post #19 -- so the 'cross-level' box is ticked, nothing to do here. (By the way, the Height Control Sensor adjusters cannot be used to adjust cross-level -- hydraulically impossible because AHC Right and AHC Left are connected when the vehicle is at rest and only the torsion bar adjusters are used when cross-leveling is required).

Hub-to-fender heights show that the vehicle is a bit low compared to the standard IH8MUD recommendation for stock vehicle as given previously -- but by itself that is not an AHC problem.

However, the Height Control Sensor readings ARE a problem -- showing a huge difference and are a cause of conflict as previously described in Post #17.

Even though monitoring "Front Wheel Step" and "Rear Wheel Step" while on the road suggests that the ECU is sending damping signals as it should to the Damping Force Control Actuators, cannot yet rule out 'fail safe' mode (also called limp mode as mentioned by @uHu). The only reason I can think of for the AHC Pump not running without one or more specific Pump-related DTC's (C1741, C1743, C1751, C1762, etc -- see "DIAGNOSTICS" section of FSM) is because of 'fail safe' mode. The AHC system will not play ball in this mode even if the AHC Pump is good. None of the mentioned DTC's are showing.

The Sensors are new and at the front include the short lead to the main harness connection above the wheel arch and hopefully all Sensors and their Connectors and Harnesses are all good. Are they genuine AISIN Sensors as supplied through a Toyota/Lexus source or are they from a different source?

I still think Sensor adjustment is essential to overcome the difference in Height Control Sensor readings, and eliminate that as a possible cause of the current malaise.

I also think that the "Active Test" needs to be tried using the description given in another attachment to Post #17. This also will tell you whether the AHC Pump is operational or not (because the ECU is bypassed in this test).

It is worthwhile to check the voltage supply at the AHC Pump by pulling the connector and using a multimeter.

The overall +B and IG voltages showing on Techstream are a worry -- will have to think further about this.

 

[suprarx7nut]

Here are the pics requested. Pics of the shocks go FL, FR, RL, RR

View attachment 2734733

View attachment 2734736

View attachment 2734746

View attachment 2734750

View attachment 2734751

Looks like the major components are present, albeit rusty.

I hope @uHu and @IndroCruise are onto something and adjusting those sensors gets you running. I would have expected to see some pump movement or an error code, but perhaps they're onto something and there's an over-riding fail safe mode that comes into play when the mismatch is that large.

 

[ParaJake]

I am running the active tests on each one of the systems on the active test screen. Im not sure what to do here. All that happens is a little screen pops up with a left and right arrow and the option to turn things on or off via the arrows. However they all show up as off initially. But when I switch them to on, they instantly go back to off. Is this how it's supposed to work?

Edit: Correction. This is popping up on some of them

 

[ParaJake]

As I try to run the active test, all of the selections are showing the above screenshot message. And when I attempt to run the active test on each one, the ACH OFF light turns on and stays solid. Is this normal?

 

[suprarx7nut]

As I try to run the active test, all of the selections are showing the above screenshot message. And when I attempt to run the active test on each one, the ACH OFF light turns on and stays solid. Is this normal?

I think the sensor height differences might be causing you problems. Adjust the sensors to more accurately reflect the vehicle height and try again.

 

[ParaJake]

I think the sensor height differences might be causing you problems. Adjust the sensors to more accurately reflect the vehicle height and try again.

How do I perform this? Do I adjust both sides to get them to equal out? Or do I adjust one side to match the other?

 

[suprarx7nut]

How do I perform this? Do I adjust both sides to get them to equal out? Or do I adjust one side to match the other?

To get started, just adjust one. I don't think it matters right now. You'll be fine-tuning them later, but let's just get the basics functioning first. Take either front sensor and move it on the slider and recheck your values. Adjust until your fronts are closer to even. Within .5" should be plenty.

Once you get that pump running, then you can fine tune all the heights.