How to reset AHC pump or bleed air from the system? (3 Viewers)

[Traveling]

Many thanks to this forum (Hoser,Hkeller,Lexusben Texasoiland Uhu in particular), I was able
after grinding a 36 mm spanner down to 8-9mm thickness to change both the rear flat
accumulators of our 2000 LC100 (not too difficult;just one sphere was a bear to get loose!).
Now I am facing a blinking OFF Heigth Control sign on the dashboard when starting the engine
with the HP hydraulic pump refusing to start.

As Texasoil says : What gets most 'techs' is lack of understanding!
we bought this LC100 when transferred to France, mainly to be able to trail a boat south to
the mediterranean . We noticed that when the load was not properly balanced on the two axle
trailer, the AHC was set to LOw ( I think with OFF sign blinking as well on dashboard).
A few visits to the Local dealers made us realised these people did not have a clue and
could be quite expensive ( talking about changing the whole system!!!).Anyway, the AHC was
resetting itself after a while.
I tried to understand how it works, with the help of my EPC disks ( remains of our HDJ80)
and a visit underneath the car and within the engine area. Hydraulics can be easily
understood, but the electronics or computer logics without a manual is just impossible.
So I bougth a FSM ( 4.2TD engine) on ebay: bad luck, it is for a UZJ!! ( without AHC).
Then I started to have this bumpy ride on the rear that can be.. a bad sign for your
finances.
I discovered HiMud forum, understood why we could have the AHC on Low when trailing; did the
test of the 7-8 marks and found a difference of 12 graduations on the reservoir !!!!,
deducted this could be due to nitrogen from the accumulators increasing in volume due to
lower pressure after channeling out of the membrane, and decided to change the accumulators.
Well,I had the local dealer to double check if the price of brand new accus was for real,and
decided to go for second hands( not easy and quite long to ship from B and B ; and ...no
local dealeryet).
By the time we found a salvaged 2005 LC ( same P/N for the accus), I had to keep using our
LC from time to time. Then this OFF sign started blinking on the dashboard with AHC set on
Low. It remained for one week, then disappeared, with pump working again . I did avoid to
use the car until we received the accus.
The day I changed them, the OFF sign was there again ( blinking one time per second
approximatively).

After changing ( the old accus membranes were indeed flat out), pump still did not work; I
tried to bleed off the pump by releasing the HP outlet ( same piping for discharge and
return); liquid go thru , but pump do not start.
Now, this is all I can do without understanding which safety sensor or which logic need to
be reset .
I did read the thread about resetting the DTC ( diagnostic trouble code) , or starting the
pump manually ; and as a first contribution , I join here a schematic of its PINs. But I am
not sure which is the proprer procedure to reset/bleed the system to have the pump
to run again ( of course I am taking the assumption our pump is still OK).
Anybody had this experience?

 

[100 TD]

Try here

https://forum.ih8mud.com/showthread.php?t=60619&highlight=ahc

if no good then use the "search" feature, I'm am sure this has been covered before.

 

[Traveling]

Thanks 100 TD for the info,
I feel I do know this thread by heart ( helped me greatly to change the accus and to understand how the system works, along with B&B website) ;and I did research extensively on this forum, lexus forums as well, but was unable to find a clear procedure how to reset the system after an ingress of air or nitrogen .
Just found info how to work the pump manually , or reset the pump with OBDII ( reason why i joines schematic of OBDII).

 

[Jim_Chow]

There is a way explained in the LX470 vol 1 manual that allows one to force the AHC height through all 16 gradations and front/rear indepently of one another. IIRC, you short a couple of pins on a plug next to the DRL relay in the engine compartment and use the AHC switches in the right sequence. Volume 1 of the FSM generally isn't as useful as volume 2, but it does contain a lot of AHC diagnostic stuff that's omitted in vol 2.

 

[Traveling]

Thanks jim, I do appreciate as i am fully in the dark in here.
Sounds like what UHU described as "the active test" to run the pump manually , from his LC100 FSM.
But his manual said it has to be done from the OBDII connector inside the vehicle compartment , close to brake pedal. ( Which could be the same wiring, engine connector being specific connection to Toyota/Lexus).

I am ready to run the pump manual as per above procedure, but I do not know if I need to reset the Diagnostic Trouble Code first ! ( again through the OBDII), or make first sure that the AHC pump cavity is properly bled off.
And , above all ..I am afraid if I do not apply the rigth sequence , that I could create a bigger problem!

 

[Jim_Chow]

Thanks jim, I do appreciate as i am fully in the dark in here.
Sounds like what UHU described as "the active test" to run the pump manually , from his LC100 FSM.
But his manual said it has to be done from the OBDII connector inside the vehicle compartment , close to brake pedal. ( Which could be the same wiring, engine connector being specific connection to Toyota/Lexus).

I am ready to run the pump manual as per above procedure, but I do not know if I need to reset the Diagnostic Trouble Code first ! ( again through the OBDII), or make first sure that the AHC pump cavity is properly bled off.
And , above all ..I am afraid if I do not apply the rigth sequence , that I could create a bigger problem!

I'm pretty sure you don't need a OBDII to perform the active test. It was a matter of shorting out a couple of pins (maybe this is what the OBDII is doing for you) and using the AHC buttons in the correct manner. At least this is how it is on the '03 Lx.

 

[Traveling]

I just realize we could be talking about the same thing; my Part Manual refer to this 16 pin connector ( where you have to short out pin 3 and 13 to initiate the active test ) as OBDII connector .

 

[uHu]

First, did you check your fuses (or rather the LCs fuses).

Do the "Active Test". You can reset the DTC first, if there still is a problem later, the DTC will come back!
The Diagnostics section in the FSM states that you can get rid of air even by doing the Active Test alone, by running the pump manually for 10 secs, by pressing the UP switch, and at the same time observing that you don't try to go over the max height level of suspension travel.

BTW, check the position of the pins in the DLC3 plug. There is a conflict between the numbering I referred to in previous posts and the one in your drawing posted above. If you use the description in my posts #72 & 73 of the thread linked to above, you should be OK.

If the pump motor does not start, you can test it by connecting it directly to 12 v by unplugging the plug to the pump motor in the engine bay.

There is also a procedure for reading any DTCs without a tester, by reading flashes of the AHC control light, in a method similar to reading morse code, just simpler....

 

[uHu]

Reading DTC of the AHC system

To read the DTC of the AHC, you connect the TC to CG (Common Ground) in the DLC3 connector;
turn on the ignition;
read the flashing of the "Height Control OFF" indicator.

Code for OK is 1 flash every 0.25 secs (4 flashes every sec)

Trouble Codes are read as flashes of 0.5 secs, with 0.5 secs dark between each, and 1.5 secs between each digit in a number.
If there is more than one DTC, there will be a pause of 2.5 secs between each code, and then a break of 4.5 secs before the whole DTC sequence starts over again.
The code is just 1 flash for numeral 1, 2 flashes for numeral 2, and so on. All the codes are 2-digit, and there seems to be no code with a zero. There are 19 codes listed in the manual, all between 11 and 64. (not in a contiguous sequence)

The codes most likely in your case are:
62 - Fluid pressure malfunction (pump does not supply fluid)
61 - ECU malfunction
51 - Continuous electric current to the ahc pump motor
43 - AHC main relay malfunction
41 - Short circuit in AHC motor relay circuit
18 - Open or short circuit in pressure sensor circuit
or 11, 12, 13 for - Open or short circuit in the height sensors

Have fun.


Added PS: Here is an attempt to illustrate the codes:

In this example, DTC 11 and 31 are indicated.
Legend:
! = flash of 0.5 sec
- = pause of 0.5 sec

-!---!-----!-!-!---!---------!---!-----!-!-!---!--------

That was the sequence two times over.

 

[Traveling]

Thanks UHU, quite clear!
Yes, I first checked the fuses (and the relays as well). All OK.
BTW, I was also going to test first the pump by applying 12V to its motor, but I reckon i get scared to do the wrong thing with all these electronics ( I really start to miss the HDJ80).

I did notice indeed there is a conflict in the PIN numbering. My schematic is coming from an HD-FTE engine manual (for land cruiser) listing the OBDE codes . I better check on this before doing the test!
Thanks again ; I'll let you know.

 

[uHu]

... to change both the rear flat
accumulators of our 2000 LC100 (not too difficult;just one sphere was a bear to get loose!)....

Just to get the lingo straight, the AHC system has one accumulator, which is a sylinder shaped container located inside the left running board. What you changed were the actual nitrogen chambers, or gas spheres. Also called gas springs, or just air springs, although we normally use that term for the rods holding the hood and liftgate up.
That's my stab at it. Sorry if it's a bit outside the subject of this thread.

 

[uHu]

Thanks UHU, quite clear!
Yes, I first checked the fuses (and the relays as well). All OK.
BTW, I was also going to test first the pump by applying 12V to its motor, but I reckon i get scared to do the wrong thing with all these electronics ( I really start to miss the HDJ80).

I did notice indeed there is a conflict in the PIN numbering. My schematic is coming from an HD-FTE engine manual (for land cruiser) listing the OBDE codes . I better check on this before doing the test!
Thanks again ; I'll let you know.

LC80 YEAH!

In the DLC3 plug, the Tc and Ts are really easy, as they are the only two "active" pins which are neighbors, and CG is in the other row, close to the center.

 

[Traveling]

Not at all, it is fair,
I realised the different wordings within the different threads and .. opted for the Texasoil ( B&B) wording ( after all it is what it is called in the oil business when such things are used !)
Here in France , they call the " accumulators" the spheres (I believe Citroen was the first to use the system; and by the way, their spheres cost pennies only).
I had the same experience as you; I bougth complete second hand systems ( speres + actuators) but replaced only the speres.

 

[Jim_Chow]

My FSM vol 1 says to perform the "active test" (ie, force the AHC front/rear up down independently), you first pop open the hood and access the DLC1 connector. It's located against the right side wall just next to the rear of the air cleaner box (looks like the DRL relay, but is about 1 foot behind it and says "diagnostics" on it). Short out the E1 and Ts pins. Now start up the engine. Within 5 sec of starting the engine, press the AHC down button at least 5 times within that 5 seconds. Now, the AHC "off" light should flash at a 0.25 sec interval. This means you are ready to perform the active test.

There are two modes to the active test. One is to raise/lower the front (one step at a time, like from N to H, then H to N, N to L, etc.). To do this, set the damper mode switch to "comfort." Now by pressing the AHC switch "down", it will lower the front. Likewise, pressing "up" will raise the front. The other mode activates the rear. Press and hold down the AHC on/off button (the one right between the AHC up/down switch and damper selector). While holding down this button, press the AHC up switch to raise the rear, AHC down switch to lower the rear. The damper switch should be in "comfort" in all cases for the active test.

The FSM warns NOT to raise the vehicle past "H".

There is a similar test for the damper "accumulators" to get it to run through all 16 steps of stiffness, but that's a different story.

BTW, this thread should be in the archive...lots of good info here.

 

[Traveling]

Well, I had to wait until today to do the job and shall let you know about the experience .

First, I bought an OBDII female connector and welded wires on Pin 3,4 and 13(numbering as per UHU fsm).
This to make the job easier as the location of the OBDII car connector (under the dash , next to pedals) seems to be perfectly suitable to contorsionnists only.
Just went underneath the dash to confirm that car connector has only connection in PINs 1,3,4,8 and 10,13 .

Shorted out pin 4 and 13 to carry the DTC reading test. Nothing! ( except that I get rid of the flashing OFF ligth after restarting the engine).
Could be a conflict between diffferent cars in Pins numbering ; will check later and inform.

Decided to work now from DLC1 ( which BTW is free of confusion as a schematic of the PINs is printed in the inside of its cover) as per Jim infos .
Shorted out Tc and E1, turned on ignition : WOUAW!! A X-mass tree! with all the dashboard ligths blinking ( ABS, belt,engine, cruise,airbag, door).
Then I had fun reading the codes ; only one : 62 i.e fluid pressure malfuction/pump does nor supply fluid ( thx UHU for yr very clear "morse" explanation).

Then I Did the active test ( shorted out Ts and E1): got the OFF indicator flashing at 0.25s. OK.
But pump refuses to run ( either front or rear).
Decided to reset the DTC. OK. Run the reading DTC test ; checked if no more code. OK no more.
Run the active test . Nothing again.
I have to reckon I starled fiddling around ,start engine, run DTC test, disconnected discharge HP piping etc , etc; no success.
Then I disconnected the electric connector to the hydraulic pump electric motor; I run the active test again and checked with meter if any voltage between the two wires when running the pump. Nada!

I feel there could be a pressure sensor bypassing the ECU ( directly connected to Pump relay). But I am working outside and had to stop due to rain.
Will have to check tonigth with my manuals which of the two wires is the positive one to try to run the pump directly under 12 V tomorrow . Will let you know my progress.


BTW, I was impressed by Jim and UHU infos; seem they got it from a FSM. I have a lot of datas and manuals ( EPC, UZJ, HD-FTE motors, etc, etc), and was not expecting to get this type of info from Toy fsm. I got conned on ebay , buying lousy staff. Where to get/buy this type of FSM ( I presume it is hard copy); will certainly help me to contribute to the forum with all the works i have to carry out!! ( I checked with toyota here, they just laughed at me!)

 

[uHu]

Any news on the pump motor?

 

[Jim_Chow]

You can order the manuals for the UZJ for both Toyota or Lexus at Toyota Material Distribution in Compton, CA. One manual I'd highly recommend is the electronic FSM...has all the schematics, connectors, harnesses, junction boxes, etc. for the electrical systems on the vehicle. IIRC, the one for the LX was only $75 plus $15 shipping (yeah, shipping is pricey considering I'm in the next state), cheaper than I expected considering how exotic the information is!

 

[Traveling]

Well, UHU
I popped out the AHC relay , checked 12V incoming power; checked continuity from relay to pump ( line is blue with black stripe, 16 or 14 gauge).
Applied power to the pump ( easy to do either by shorting out AHC relay , or powering directly from battery nearby to relay).
But I did not disconnect the HP piping from the Pump discharge ( still evaluating how to avoid/control a mess in the engine bay if/when running the pump with discharge open ).
Applied power to the pump a few times ,without ,then with engine running; the pump seems to run fine ( obviously rotating), with at one stage this typical valve opening "hissss" sound coming from below).But no change at all.
Nevertheless quite a relief when you know how much a brand new one costs!

Then I went to go and check these wires going from the two other pump connectors ( pressure switch and level sensor or temp sensor or???) to - I guess- the AHC ECU deep in the cab.
And of course I Twisted my neck!!

So I am going to have a few days before I can go back and see.
Meanwhile I will try to figure out how this HP multi piston pump is operating ( can it really be the one in cause , with cavity requiring to be bled, and how).
If not I will have to find which info/sensor feeding the AHC ECU tells the computer not to provide power to the HP Pump, to be sure of the reason why system is stuck.

Thanks for inquiring , and also for the very clear infos you provided. That was great help!

Thanks Jim for the info on Electronic FSM . I am going to contact them .

 

[Jim_Chow]

The LX schematic shows the temp sensor has 3 wires, a G-Y (goes to J/B 7D, pin 37), R-Y (to J/B 7D pin 33, which connects to J/B 7C pin 14 and goes to the AHC ECU), and R-B (pin 28 of J/B 7D). The R-W is the input wire from the fluid prssure sensor to the ECU.

The temp sensor has 2 wires: G-Y (goes to J/B 7D, pin 36) while the G-R goes to J/B 7D, pin 32, which then connects to J/B 7C pin 15 and goes to AHC ECU pin 3B.

FYI, J/B 7 is the one behind the glove box above the right cowl J/B (looks to be about behind the top right vent). J/B 7 has 3 plugs going into it. THe large one is a 40 pin from engine room #2 wire. This is how the temp and pressure sensors link w/ the inside of the vehicle. If you pull off this wire and look at the J/B, you'll see pin 21 through 40 on the top row, then 1...20 on the bottom row (raster style). J/B 7C is the connector that goes in the middle in the opposite side, has 20 pins (10...1 top row, 20..11 bottom row, raster style). J/B 7B is the other one right next to 7C, has 16 pins (8..1 top row, 16..9 bottom row).

Other thing of interest...a control valve assembly, which connects to the AHC ECU via a number of harnesses leading all the way from the rear left suspension support area all the way up to the dash wire and floor No. 1 (in front of [closer to firewall] left kick panel near the bottom of it). There is an accumulator solenoid that also goes via this connection to the ECU.

BTW, I'm looking at the section in the FSM vol2 about how to change the AHC pump motor. It says you first bleed the AHC height control accumulator (the cylinder under the left side front rail), then you can remove the AHC hydraulic line to the pump. It then tells you how to basically strip the pump and disassemble it, replace the seals, etc. Then it says installation in the same in reverse. Then fill the pump & motor resevoir w/ AHC fluid and bleed the system.

In the bleeding section, it says in bold print, "Notice: When the resevoir is empty or after the AHC pump & motor is replaced or removed, starting engine may cause air inflow in the AHC fluid line. In this condition, the AHC system cannot be operated even if the fluid is poured into the tank. If this happens, raise the vehicle height of the front or rear wheel by conducting the active test and activate the AHC pump & motor for about 10 seconds." You then put AHC in "N", check that the pump has stopped, shut off engine, then bleed each wheel, then start the engine and check fluid level. Did you run the active long enough?

 

[Traveling]

Thanks Jim for these great infos.
I am still for a long ride, but I think it will be good I make a resume of all of these good info at the end ( AHC troubles appear to be quite common cases on these machines).I am taking photos for that.

As I said, I initially reset the DTC, and did not get anymore codes since.
I cannot run an active test as the pump refuses to run under the test conditions ( no power; safety device acting on The ECU? or maybe due to ECU itself ?).
So I did run the AHC Pump directly on 12 V and I was afraid to let it run for more than a few secs since i was not sure of pump lubrication ( ref. cost of a toyota pump!).
After your infos , I was convinced I could run the pump for 15 secs manually with and without engine running.

But no progress!

So I disconnected the HP discharge piping and run the pump manually with 12V; the hydraulic fluid did not get out at once , but I had progressively a continuous flow. I stopped the pump and reconnected the pipe.... and cleaned the mess. I guess I may now consider the pump cavity free of air.

But the system still refuses to work and still no DTC codes.
Not likely to come from the pressure and temp sensors.
Seems the central control accumulator( appropriate name as it delivers stored pressure to each of the 4 actuators) does not take fluid .
My next ops will be to bleed the central accu and the 4 suspensions; and eventually run the pump with all the bleeders open to be sure that air in no longer the problem.

Where is my FJ40!!!!!!