Builds eatSleepWoof's '14 LX (1 Viewer)

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Spoke with the dealer. They tested all of the components and found an issue with the AHC pump's motor. They said it was working when I brought the vehicle in, and at a later time too, but was not responding later on. They've no idea how what they did could have affected the motor (neither do I), but they're installing a new motor, reservoir, etc. right now, and will bleed the system after everything is installed. Fingers crossed this does the trick.

Have to say I'm impressed with how they're handling this. Zero attempts to shift blame to me (AHC lift/off-roading/etc.) and very polite, professional service throughout. A pain to be without the LX, but mistakes happen, and they're doing what they can to make it right.
 
Glad it worked out. I try to avoid my dealer - but when I do bring it in they are generally excited to see an LX that's clearly being used to it's potential. They love seeing built trucks.
 
Lexus service usually values the customer. At a price, of course.
I wouldn't expect the pump to fail just because, but I guess it could . . .
 
Got another call from the dealer. New pump/motor is in, no change. Still stuck in low. They're reaching out to Lexus Technical Assistance again and sending a loaner to me. Something tells me my long-awaited and upcoming camping weekend won't be happening. So frustrating.
 
Latest update from the dealer:

"So even the engineers at this point aren’t sure why your vehicle isn’t working as hydraulically and manually all the pressure readings electrical readings from the pumps and relays are showing normal and indicating the vehicle should be lifting up as designed. They have indicated to us that the next step will be further diagnosis or the ECU that controls the AHC system. What we have to do is essentially take an ECU from a vehicle we know is functioning and do readouts of its data and compare it to your vehicle to see where the discrepancy lies. We have a donor vehicle lined up to test functions off of but it won’t be available until next week so we won’t be able to return your vehicle until that point. Is there any other information you can think of related to when this started not functioning?

I understand this isn’t convenient for you as you require your truck but we hope to get this corrected soon as this is incredibly uncommon for these vehicles and we have never encountered this issue before."
 
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Man that sucks. I doubt air bubbles would survive a full replacement, so that reason is out. I guess we can rule out a blocked line too?

Must be a sensor . . .
 
Man that sucks. I doubt air bubbles would survive a full replacement, so that reason is out. I guess we can rule out a blocked line too?

Must be a sensor . . .

Wouldn't a bad sensor be caught via the pressure (& other) readings?
 
Wouldn't a bad sensor be caught via the pressure (& other) readings?
Perhaps. I've spent some time looking at the AHC page in techstream and most of it is 'real time'; it's hard to know what the baselines and ranges are or should be.

I'm just thinking about what happened:
Scenario:
It worked fine.
It was 'flushed'. <- change in state
It won't change mode to H. (Is that right? You can go from L to N?)

So, the pump functions, it can increase pressure enough to get to N. But not enough to get to H.

Some possible reasons why you can't get to H:
1) A line is blocked etc and the pressure at the pump is fine, but isn't making its way to the manifolds etc. -> ?
2) The pump is physically unable to raise the pressure more -> Troubleshoot by replacement, no change
3) A sensor is telling the pump it is at "H' level or "H' pressure, and it shuts off before achieving -> ?
4) Very heavy load in car exceeding hydraulic capacity -> Easily dismissed
5) A pressure leak (blown seal etc) preventing pressure built/maintain to "h" level -> Probably easily noticed by no fluid on ground or hissing sounds etc
6) ECU is screwed up!!!! -> ?

There is some history on the board of an AHC ECU not setting height correctly at all corners and being replaced.

I am doubtful that the 'flush' screwed up the ECU, however you did have other work done so maybe there was some potential for a ground or short or something.
 
Perhaps. I've spent some time looking at the AHC page in techstream and most of it is 'real time'; it's hard to know what the baselines and ranges are or should be.

I'm just thinking about what happened:
Scenario:
It worked fine.
It was 'flushed'. <- change in state
It won't change mode to H. (Is that right? You can go from L to N?)

So, the pump functions, it can increase pressure enough to get to N. But not enough to get to H.

Some possible reasons why you can't get to H:
1) A line is blocked etc and the pressure at the pump is fine, but isn't making its way to the manifolds etc. -> ?
2) The pump is physically unable to raise the pressure more -> Troubleshoot by replacement, no change
3) A sensor is telling the pump it is at "H' level or "H' pressure, and it shuts off before achieving -> ?
4) Very heavy load in car exceeding hydraulic capacity -> Easily dismissed
5) A pressure leak (blown seal etc) preventing pressure built/maintain to "h" level -> Probably easily noticed by no fluid on ground or hissing sounds etc
6) ECU is screwed up!!!! -> ?

There is some history on the board of an AHC ECU not setting height correctly at all corners and being replaced.

I am doubtful that the 'flush' screwed up the ECU, however you did have other work done so maybe there was some potential for a ground or short or something.
It just seems to me that 1) or 3) is way more likely than 6). Right? Flushing -> particles disturbed in line -> blockage in manifold -> Pressure is reduced
 
Double post.
 
It just seems to me that 1) or 3) is way more likely than 6). Right? Flushing -> particles disturbed in line -> blockage in manifold -> Pressure is reduced
Or maybe in the line right after the pump, so the pump replacement didn't affect.
 
Just to be clear, the car is stuck in low, and cannot get up to N, or to H.

I tried centre diff lock and low range - both worked fine, but there was no height change in low range (normally goes up a bit).
 
Just to be clear, the car is stuck in low, and cannot get up to N, or to H.
Ok. I thought you had it in "high N" immediately after the service.
Can't build pressure -> sensor says stop, or line blocked. I think the logic tree still the same . . .
 
Can you hear the pump running?
 
Is it the same error as before? I fully believe this is due to tech incompetence. It probably was just underfilled or needed bleeding - due to tech incompetence. There's specific steps that need to be carried out to make sure there's enough fluid level.

1588969641394.png


The specific issue is that the ECU does not see the AHC pump increasing fluid pressure within .6 seconds. Potentially due to insufficient reservoir fluid after burping air from the system. No increased pressure - no raise. They were likely chasing the wrong thing, but makes sense that they tried to replace the pressure pump.

If the same DTC remains now, I'm still suspicious they bleed or filled the system right. Alternatively, has the pressure sensor been checked or replaced?

It's almost never ever the ECU.
 
Is it the same error as before? I fully believe this is due to tech incompetence. It probably was just underfilled or needed bleeding - due to tech incompetence. There's specific steps that need to be carried out to make sure there's enough fluid level.

View attachment 2299819

The specific issue is that the ECU does not see the AHC pump increasing fluid pressure within .6 seconds. Potentially due to insufficient reservoir fluid after burping air from the system. No increased pressure - no raise. They were likely chasing the wrong thing, but makes sense that they tried to replace the pressure pump.

If the same DTC remains now, I'm still suspicious they bleed or filled the system right. Alternatively, has the pressure sensor been checked or replaced?

It's almost never ever the ECU.

Same error as far as I'm aware.

My gut feeling is the same as yours: they didn't do the procedure properly. Considering that the tech had wanted to remove the rear bumper and couldn't find the bleed screws...

On Tuesday evening I did send them this video, as well as numerous DIY fluid-flush guides I found on this forum, and asked them to have a master Lexus technician re-do the fluid swap properly. I explained the importance of not having an empty reservoir and not sucking air into the system, and shared various AHC-related docs I found. They had replied with:

"The technician working on your vehicle is one of our master technicians and he has performed the bleeding procedure you provided after the new motor and reservoir were installed."

Yeah...
 
Uh, I hate the feeling of being a captive victim. It's unfortunate, but at their mercy at the moment. Luckily this is the Lexus dealership and they'll make it right one way or another.

Without the AHC pressure pump working, there is no way to bleed the system. It starts and ends with that component.
 
Being without my vehicle (on my birthday weekend, no less) is a horrible feeling. All plans went out the window. I've always had an emotional attachment to my vehicles and being unable to use them is very unpleasant. I even miss driving my vehicles when I'm on a vacation. Probably a very strange thing to describe to folks that see their vehicles as appliances.

I've sent a follow-up email specifically asking whether the pressure sensor has been checked or replaced.

And I've decided that we're not going to be sitting at home all weekend, and the NX300 loaner will be seeing gravel roads over the next two days. A lot of them.
 
Got a reply: "The pressure sensor was checked and was showing normal operation within factory specs."
 

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