LX470 AHC issues - pressure sensor 1998 Vs. 2002 (1 Viewer)

[IndroCruise]

IndoCruise -update 7/9/24

Thank you , once again for your detailed description and explanations.... they are my lifeline after 5 months of this frustration.! !

I removed the return valve based on the pictures from Russia last night and attached photos of what it looks like. I too, think something is messed up , and blocking this little valve from functioning. I think the screen in it would prevent such damage since fluid returning to the tank WILL pick up contaminants from a disturbed, open system...like mine. Now that I see how the Russians disassembled the end of it, by prying the end off with a screwdriver as a wedge, I will attempt that today. I cannot understand Russian, but I sure can follow the pictures and his hand gestures as to what to do. IF THIS DOES NOT WORK AND UPON REASSEMBLY, IT CAN NOT PRODUCE PRESSURE, THEN I WILL BE LOOKING FOR A USED PUMP FULL ASSY, & use the part 48905-60010 ($800 ) from a used full assy hole Pump assembly 48910-60012! Indocruise, I am willing to purchase one of your old pump assy, or just the return valve from a working pump, if you are willing to sell it. This is going to be a rare find unless someone from this group is reading this.
View attachment 3673487View attachment 3673488View attachment 3673489View attachment 3673490

For anyone that has been reading this thread or following this adventure for the last 5 months, PLEASE LET ME KNOW IF YOU HAVE A USED Pump assembly 48910-60012 FOR SALE, I NEED IT! . Please let me know by text or call me!

GREAT ORIGINAL PICTURES @suprasvobodea !! My old AHC Pump Assembly 48910-60012 is reserved for my son-in-law in Western Australia, so I am not able to let it go. Hopefully you can find an alternative closer to you in Dallas, Texas?

It may be worthwhile to check or post a request in the "Classified" sections of this Forum??

Just thinking about your words -- "I think the screen in it would prevent such damage since fluid returning to the tank WILL pick up contaminants from a disturbed, open system...like mine".

This is true for AHC Fluid already in the AHC Tank. AHC Fluid returning from elsewhere in the system (for example, after auto self-levelling or dropping N > LO or HI > N) must first pass through the Return Valve on its way to the AHC Tank, as indicated in the diagram and explanation below.

This returning AHC Fluid does not pass through the strainer in the Return Valve until it is recirculated later, from the AHC Tank by the AHC Pump.

It seems that all was well until repairs some months ago, such as your change-outs of all 'shock absorbers', all 'globes' and the Height Control Accumulator. It seems possible that you have been unlucky enough for sludge or debris in returning Fluid from elsewhere in the system to have affected your Return Valve at that time. Or it may be that there is a fault in the Return Valve.

Now that the Return Valve is out of the vehicle, it may be possible to replicate and test the two different flow directions [meaning, (1) Fluid returning from the AHC system to the Tank, and, (2) Fluid being sent by the Pump from the Tank tp the AHC system]. Maybe this could be done in both directions by blowing through the Return Valve, or using a jet of compressed air, or devising a method to pump fluid.

Otherwise, dis-assembling then examining and cleaning the Return Valve seems to be the next best step.

Aside from the YouTube clips provided previously, reported problems with the Return Valve are unusual. More pictures of the dis-assembled Return Valve would be very interesting to see -- please post more pictures when you can ....

 

[Moridinbg]

Following with great interest. This still looks surprisingly similar to my issue. I too had greatly disturbed the system prior to the first issues - with the chassis removed the AHC was disassembled down to the pipes and everything.

Sometime next week I should be getting a bunch of stuff from Impex and will be replacing the globes, one front shock, the accumulator and all O-rings and grommets that I was able to track down in the part diagrams. I have a spare assembly, so might try to extract a valve from that or mine too, if that turns out to be the case with yours. Sorry, can't ship one to you as I am in Europe and in deep sh1t with the AHC, just as you.

 

[suprasvobodea]

GREAT ORIGINAL PICTURES @suprasvobodea !! My old AHC Pump Assembly 48910-60012 is reserved for my son-in-law in Western Australia, so I am not able to let it go. Hopefully you can find an alternative closer to you in Dallas, Texas?

It may be worthwhile to check or post a request in the "Classified" sections of this Forum??

Just thinking about your words -- "I think the screen in it would prevent such damage since fluid returning to the tank WILL pick up contaminants from a disturbed, open system...like mine".

This is true for AHC Fluid already in the AHC Tank. AHC Fluid returning from elsewhere in the system (for example, after auto self-levelling or dropping N > LO or HI > N) must first pass through the Return Valve on its way to the AHC Tank, as indicated in the diagram and explanation below.

This returning AHC Fluid does not pass through the strainer in the Return Valve until it is recirculated later, from the AHC Tank by the AHC Pump.

It seems that all was well until repairs some months ago, such as your change-outs of all 'shock absorbers', all 'globes' and the Height Control Accumulator. It seems possible that you have been unlucky enough for sludge or debris in returning Fluid from elsewhere in the system to have affected your Return Valve at that time. Or it may be that there is a fault in the Return Valve.

Now that the Return Valve is out of the vehicle, it may be possible to replicate and test the two different flow directions [meaning, (1) Fluid returning from the AHC system to the Tank, and, (2) Fluid being sent by the Pump from the Tank tp the AHC system]. Maybe this could be done in both directions by blowing through the Return Valve, or using a jet of compressed air, or devising a method to pump fluid.

Otherwise, dis-assembling then examining and cleaning the Return Valve seems to be the next best step.

Aside from the YouTube clips provided previously, reported problems with the Return Valve are unusual. More pictures of the dis-assembled Return Valve would be very interesting to see -- please post more pictures when you can ....

View attachment 3673894

IndoCruise

Well, you were right about the RETURN VALVE !!! The simple fact that I could block the outlet with my finger was the HUGE RED FLAG !! After removing the return valve, I just inserted the little tube into the nozzle on a break cleaner can (it is high-pressure aerosol!!) and squirted it out the side holes ( seen in the diagram picture above !) I then re-inserted the valve back into the body and put the tank on with some fluid. I applied 12V to the pump and it shot out a stream, Then I attempted to "deadhead" the outlet and there was NO WAY I COULD STOP THE FLUID! IT SPRAYED ALL OVER! . So I KNEW that this was one of the issues! I re-inserted the valve & then used the active test and pressed DOWN 5 times to start the test. I pressed UP and the front shocks started to rise! I had a pressure of ~ 3 on TECHSTREAM! I then stopped holding the UP switch. I pressed down then and it went back down, but then I got the 1762 code again.

<<UPDATE 7/17

Moridinbg

Well.... I have THe GOOD , The Bad and the Ugly news to report ..


First... THE GOOD ...

It WAS the return valve that was blocked with .... something !! After I removed it, I inserted a tube from brake cleaner in the end, and with the high pressure in the brake cleaner cans, it shot out both side holes ( see the diagram ) After I installed it back in the assembly . primed the base by pouring oil in the small opening where the tank sits in, and angelling it so bubbles would come out the opening.... I tested with 12V and WOW!! I finally could not hold back the outflow... with my thumb !!!!! SO... I knew that was ONE of the issues that was finally resolved. So I do not need a spare return valve.!

Next, I performed the ACTIVE TEST and pressed DOWN 5+ times immediately to initiate the test. When I pressed UP - once ( not holding ) the FRONT started pumping and RISING !!! I got it to almost 0.4 height control sensor on TECHStream readout and 3+ Kpa pressure! & 0.0 on the accumulator sensor.
However, when I pressed and HOLD the UP switch to activate the rear shocks, ... the front struts dropped back to the stops and the rears did NOTHING! I checked the front globes, there was a tiny bit of air. I then check the accumulator - NOTHING. then the rear globes... NOTHING ...

Since I have TECHSTREAM, I did all the ACTIVE tests,,, life the front & rear Leveling solenoids,(SLFL) (SLRL) the Front and rear gates (SLFG) & SLRG)
The funny thing is, the REAR SLRL won't activate..?!!! Which I thought was strange.

This might be the reason why the REAR shocks failed to rise after the fronts did!! There is NO OIL BEING PUMPED TO THE REAR SHOCKS! OR THE ACCUMULATOR.

What are your thoughts and questions about why the REAR globes won't work, but the fronts will? What should I check next?? I NEED TO GET THIS LX WORKING SO I CAN LEAVE FOR WISCONSIN TO SEE MY MOTHER BY THIS SUNDAY! I feel I am SO CLOSE ...... I have all the new parts... i can get the fronts to raise and NOT throw a 1762 code for a while ( eventually it does !!

 

[suprasvobodea]

Following with great interest. This still looks surprisingly similar to my issue. I too had greatly disturbed the system prior to the first issues - with the chassis removed the AHC was disassembled down to the pipes and everything.

Sometime next week I should be getting a bunch of stuff from Impex and will be replacing the globes, one front shock, the accumulator and all O-rings and grommets that I was able to track down in the part diagrams. I have a spare assembly, so might try to extract a valve from that or mine too, if that turns out to be the case with yours. Sorry, can't ship one to you as I am in Europe and in deep sh1t with the AHC, just as you.

<<UPDATE 7/17

Moridinbg

Well.... I have THe GOOD , The Bad and the Ugly news to report ..


First... THE GOOD ...

It WAS the return valve that was blocked with .... something !! After I removed it, I inserted a tube from brake cleaner in the end, and with the high pressure in the brake cleaner cans, it shot out both side holes ( see the diagram ) After I installed it back in the assembly . primed the base by pouring oil in the small opening where the tank sits in, and angelling it so bubbles would come out the opening.... I tested with 12V and WOW!! I finally could not hold back the outflow... with my thumb !!!!! SO... I knew that was ONE of the issues that was finally resolved. So I do not need a spare return valve.!

Nest, I performed the ACTIVE TEST and pressed DOWN 5+ times immediately to initiate the test. When I pressed UP - once ( not holding ) the FRONT started pumping and RISING !!! I got it to almost 0.4 height control sensor on TECHStream readout and 3+ Kpa pressure! & 0.0 on the accumulator sensor.
However, when I pressed and HOLD the UP switch to activate the rear shocks, ... the front struts dropped back to the stops and the rears did NOTHING! I checked the front globes, there was a tiny bit of air. I then check the accumulator - NOTHING. then the rear globes... NOTHING ...

Since I have TECHSTREAM, I did all the ACTIVE tests,,, life the front & rear Leveling solenoids,(SLFL) (SLRL) the Front and rear gates (SLFG) & SLRG)

The funny thing is, the REAR SLRL won't activate..?!!! Which I thought was strange.

This might be the reason why the REAR shocks failed to rise after the fronts did!! There is NO OIL BEING PUMPED TO THE REAR SHOCKS ! OR THE ACCUMULATOR.

What are your thoughts and questions about why the REAR globes wont work , but the fronts will?

 

[IndroCruise]

IndoCruise

Well, you were right about the RETURN VALVE !!! The simple fact that I could block the outlet with my finger was the HUGE RED FLAG !! After removing the return valve, I just inserted the little tube into the nozzle on a break cleaner can (it is high-pressure aerosol!!) and squirted it out the side holes ( seen in the diagram picture above !) I then re-inserted the valve back into the body and put the tank on with some fluid. I applied 12V to the pump and it shot out a stream, Then I attempted to "deadhead" the outlet and there was NO WAY I COULD STOP THE FLUID! IT SPRAYED ALL OVER! . So I KNEW that this was one of the issues! I re-inserted the valve & then used the active test and pressed DOWN 5 times to start the test. I pressed UP and the front shocks started to rise! I had a pressure of ~ 3 on TECHSTREAM! I then stopped holding the UP switch. I pressed down then and it went back down, but then I got the 1762 code again.

I tried clearing 1762 repetitively, over and over. But now it will not work again! I am about to go back outside now & will attempt to put 12V directly to the pump while putting 12V to the accumulator solenoid to override the "failsafe " and fill the accumulator ( ...Now that there is pump pressure to do so!!! ) This is will fill the accumulator and should register pressure on techstream. What is so troubling is, WHY DID IT WORK BRIEFLY BY FILLING THE FRONT SHOCKS, AND THEN when I released the UP switch and pressed down, ( it came back down.... but now it won't work when I press UP ??????????!) I know there is air in the system, but I would like to know WHY it worked when I first assembled and tried it , but now it wont! ?

Well, that seems like very good progress!!

It may be that either

(i) your good work has cleared the Return Valve

OR

(ii) the Return Valve is faulty and it has become stuck again (in which case either the Return Valve or the whole housing will need to be replaced).

To confirm which of these alternatives is correct, suggest as a first step repeat the test of the Return Valve by detaching the steel delivery pipe and running the AHC Pump again.

If volume and pressure from the Pump delivered through the Return Valve are good, then move on to thinking about DTC C1762 (no point in proceeding further without first reconfirming the AHC Pump delivery volume and pressure).

Let's assume that this test has been repeated and the Pump is confirmed as good ....

Then as previously advised, avoid worrying about the "Active Test" -- it WILL NOT work when DTC C1762 is present.

Suggest now focus on bleeding air, using the sequence as previously advised in my Post #132 in this thread. This will take many repetitions.

Suggest ignore the Height Control Accumulator for now. The Height Control Accumulator is only recharged by the AHC Pump AFTER a raise cycle, not at the beginning of a raise attempt. It will recharge when you finally get the air out of the system by bleeding -- repetitively over and over and over again -- and after the vehicle finally raises.

Applying power at this stage to the solenoid on the Height Control Accumulator is a distraction -- because it does not help get air out of the system. The Height Control Accumulator is empty of fluid and air -- because the internal piston is pushed to the forward end by the nitrogen charge behind the piston.

It is worthwhile to experiment a bit --- try to force the bleed with the the furthest from the Pump bleeder valve open (LHS Rear) and with the AHC Pump operating AND with the engine running even if using a direct 12volt supply to the AHC Pump. The reason for this is that it is necessary to push fluid past the Levelling Valves (which are "normally closed") -- and I don't know if this can happen just with Pump pressure -- I suspect that the Levelling Valves have to be opened by the ECU and for this to happen the engine needs to be running and DTC's cleared.

If it works -- good -- if not, then repetitive perseverance with attempted raises (just with the UP button within the 0.6 seconds before DTC 1762 activates), then clearing the DTC and repeat over and over.

It is not surprising that an initial start was achieved and then stopped. Bear in mind that during a raise the Front and Rear Levelling Valves operate alternately and the vehicle raises in small steps (which are not always visible) Front then Rear then Front then Rear, repetitively. For example, all it takes is a switch from the Front to Rear (which is internally controlled by the ECU), then air in the Rear AHC system may cause the Pump to struggle to build pressure quickly enough (within 0.6 seconds), then DTC C1762 reappears, and the AHC system stops until the DTC is cleared.

The summary is that if there is confidence in the AHC Pump delivered flow and pressure through the Return Valve, then the next step is repetitive bleeding efforts, using the suggestions in Post #132 or any alternative suggestions that may be offered.

 

[suprasvobodea]

Well, that seems like very good progress!!

It may be that either

(i) your good work has cleared the Return Valve

OR

(ii) the Return Valve is faulty and it has become stuck again (in which case either the Return Valve or the whole housing will need to be replaced).

To confirm which of these alternatives is correct, suggest as a first step repeat the test of the Return Valve by detaching the steel delivery pipe and running the AHC Pump again. ( WILL DO )

If volume and pressure from the Pump delivered through the Return Valve are good, then move on to thinking about DTC C1762 (no point in proceeding further without first reconfirming the AHC Pump delivery volume and pressure).

Let's assume that this test has been repeated and the Pump is confirmed as good .... hopefull - will reply later this afternoon when i get to work on it.

Then as previously advised, avoid worrying about the "Active Test" -- it WILL NOT work when DTC C1762 is present.

Suggest now focus on bleeding air, using the sequence as previously advised in my Post #132 in this thread. This will take many repetitions.

Suggest ignore the Height Control Accumulator for now. The Height Control Accumulator is only recharged by the AHC Pump AFTER a raise cycle, not at the beginning of a raise attempt. It will recharge when you finally get the air out of the system by bleeding -- repetitively over and over and over again -- and after the vehicle finally raises. Understand- yes i now see this after all these months workgin on it.

Applying power at this stage to the solenoid on the Height Control Accumulator is a distraction -- because it does not help get air out of the system. The Height Control Accumulator is empty of fluid and air -- because the internal piston is pushed to the forward end by the nitrogen charge behind the piston.

It is worthwhile to experiment a bit --- try to force the bleed with the the furthest fron the Pump bleeder valve open (LHS Rear) and with the AHC Pump operating AND with the engine running even if using a direct 12volt supply to the AHC Pump. The reason for this is that it is necessary to push fluid past the Levelling Valves (which are "normally closed") -- and I don't know if this can happen just with Pump pressure -- I suspect that the Levelling Valves have to be opened by the ECU and for this to happen the engine needs to be running and DTC's cleared. YES. that might be the case with leveling valves, and forcing fluid to them , but 12 v direct and runing engine might actuallhy work . IF IT DOES>>> THEN WE JUST SAVED THE NEXT GUY , A TON OF TIME AMD FRUSTRATION

If it works -- good -- if not, then repetitive perseverance with attempted raises (just with the UP button within the 0.6 seconds before DTC 1762 activates), then clearing the DTC and repeat over and over.

It is not surprising that an initial start was achieved and then stopped. Bear in mind that during a raise the Front and Rear Levelling Valves operate alternately and the vehicle raises in small steps (which are not always visible) Front then Rear then Front then Rear, repetitively. For example, all it takes is switch from the Front to Rear (which is controlled by the ECU), then air in the Rear AHC system may cause the Pump to struggle to build pressure quickly enough (within 0.6 seconds) and then DTC C1762 reappears.

The summary is that if there is confidence in the AHC Pump delivered flow and pressure through the Return Valve, then the next step is repetitive bleeding efforts, using the suggestions in Post #132 or any alternative suggestions that may be offered. THANK YOU INDOCRUISE... I AM ANXIOUS TO TRY THESE THINGS LATER THNIS AFTERNOON .

Indocrusise >> Please see replies in BLUE above

 

[IndroCruise]

Indocrusise >> Please see replies in BLUE above

@suprasvobodea --
AHC bleeding may be assisted with the device discussed by @wrigh003 at Post #17 at this link:

Front AHC Shock Leak

Hello all, Looking for a few opinions on this. I went camping this weekend, parked the LX Friday and didn't move it all weekend, came out Sunday morning and it looked like this; The front was noticeably lower and there was a big puddle of AHC oil just behind the front passenger tire. After...

forum.ih8mud.com

@wrigh003 may be able to advise whether the AHC system has to be operating to open the "normally closed" Levelling Valves in the Control Valve Assembly to allow fluid to pass (ultimately from the AHC Tank), or, whether fluid somehow is drawn past the closed Levelling Valves anyway??

AHC Hydraulic Circuit with vehicle at rest, AHC system not operating, Levelling Valves closed, operating as check valves to hold vehicle height:

 

[suprasvobodea]

Well, that seems like very good progress!!

It may be that either

(i) your good work has cleared the Return Valve

OR

(ii) the Return Valve is faulty and it has become stuck again (in which case either the Return Valve or the whole housing will need to be replaced).

To confirm which of these alternatives is correct, suggest as a first step repeat the test of the Return Valve by detaching the steel delivery pipe and running the AHC Pump again. I checked it. AT FIRST it was plugged again when i tried to block it with my thumb. ! Then i let it run for 8-12 sec & blocked again , only this time I COULD NOT! it SPRAYED ALL OVER LIKE IT SHOULD WHEN I TRIED! So pump is working. I suppose i should try this again ( if i cannot stop the 1762 code from tripping)

If volume and pressure from the Pump delivered through the Return Valve are good, then move on to thinking about DTC C1762 (no point in proceeding further without first reconfirming the AHC Pump delivery volume and pressure). It does now... but since it got plugged once again.. now im starting to wonder what is going on with my system/

Let's assume that this test has been repeated and the Pump is confirmed as good ....

Then as previously advised, avoid worrying about the "Active Test" -- it WILL NOT work when DTC C1762 is present.- Actuall i DID GET IT TO WORK . ! That is how i was able to make the Front globes build pressure !!! ( SEE PHOTO) This happend when did the 1st step in the procedure of ACTIVE test- press UP - once. - which riases the front . THen press UP and HOLD it- which raises the rears. HOWEVER the rear did not raise. BUT the fronts went up even more! YOu can see the height are almot to 0.0" !! That is the most preogress i have had in 5 months! But then it fell back down . when i pressed DOWN , and stayed down and threw the 1762 code and would not go back UP again.! So what do you make of this...?

Suggest now focus on bleeding air, using the sequence as previously advised in my Post #132 in this thread. This will take many repetitions.

Suggest ignore the Height Control Accumulator for now. The Height Control Accumulator is only recharged by the AHC Pump AFTER a raise cycle, not at the beginning of a raise attempt. It will recharge when you finally get the air out of the system by bleeding -- repetitively over and over and over again -- and after the vehicle finally raises.

Applying power at this stage to the solenoid on the Height Control Accumulator is a distraction -- because it does not help get air out of the system. The Height Control Accumulator is empty of fluid and air -- because the internal piston is pushed to the forward end by the nitrogen charge behind the piston. Understood and you are right - not doing this anymore

It is worthwhile to experiment a bit --- try to force the bleed with the the furthest from the Pump bleeder valve open (LHS Rear) and with the AHC Pump operating AND with the engine running even if using a direct 12volt supply to the AHC Pump. The reason for this is that it is necessary to push fluid past the Levelling Valves (which are "normally closed") -- and I don't know if this can happen just with Pump pressure -- I suspect that the Levelling Valves have to be opened by the ECU and for this to happen the engine needs to be running and DTC's cleared. I tired this after clearing the code, and strarting the engine with ACTIVE test first to avoid immeditaly throwing the 1762. If i do that now , i do NOT immeditaly get 1762, but if i just start it normally, i get it immediatly . ( confimred with Techstream connected) . WHen i pressed UP just once , i actually got the front to raise . I took a picture on TECHSTREAM to show you, When i pushed UP and HOLD it , the front kept going up , but when i press UP and hold it, the TSM test procecdure states that the REARS are suppose to raise .. but they did now move and NO pressure what shown on techstream ( SEE PHOTO)

This is worrysome, as i could NOT get the leveling for rear to move. HOWEVER< when i performe the ACTIVE TEST featur of teck stream , which allows you to trigger the Motor relay, AHC relay, and the 4 leveling and gate valves. I did get them fronts to turn on and off. however only the rear gate valves would function ... which is VERY strange. Thats probably why the rears did not raise...... so whatsup with that ,,??

If it works -- good -- if not, then repetitive perseverance with attempted raises (just with the UP button within the 0.6 seconds before DTC 1762 activates), then clearing the DTC and repeat over and over. It did NOT work ....

It is not surprising that an initial start was achieved and then stopped. Bear in mind that during a raise the Front and Rear Levelling Valves operate alternately and the vehicle raises in small steps (which are not always visible) Front then Rear then Front then Rear, repetitively. For example, all it takes is a switch from the Front to Rear (which is internally controlled by the ECU), then air in the Rear AHC system may cause the Pump to struggle to build pressure quickly enough (within 0.6 seconds), then DTC C1762 reappears, and the AHC system stops until the DTC is cleared.

The summary is that if there is confidence in the AHC Pump delivered flow and pressure through the Return Valve, then the next step is repetitive bleeding efforts, using the suggestions in Post #132 or any alternative suggestions that may be offered. QUESTION>>> I have to perform the ACTIVE TEST , everytime to prevent the 1762 immeditaly triggering when turing on the engine. If I clear 1762, do active test then whiule the engine if running, when i press the DOWN switch just once ,... it does NOT triver 18762.. Thats how i was able to get the pressire to the fronts which you see in the photo above!! W/O peforming active test, i would never have got a chance to even get this for. This is wjhy i ask this,, question... you do not say to do this in your post #132.. Was that just an assumed step that i would do ?

I am not getting ANY fluid to the rear globes to even try to bleed!! Something is wrong.... but I don't have the experience to know what to do next.? INDOcRUISE .- what should I check next? Im running outta time. I need to get this running by Wednesday so I can drive 1000 miles up to Wisconsin!!
UPDATE 7-21- INDOCRUISE
To clarify and simplify I have replied in BLUE above

 

[Moridinbg]

That sounds like a solenoid issue. Have you tried the active test in Techstream that opens and closes it? It keeps it open for about a second and then automatically closes it. You can hear it click. If that doesn't work you could apply 12V directly and see if that does it, combined with forcing the pump to run.
Considering you had debris in the return valve, it is possible that there might be a contamination in the system that affects the solenoids.

My huge Impex order is as the customs and I am anxious to see what is going on with my AHC. The return valve by itself sounds super promising, as I am facing the same issue as you, weak stream and all. Maybe my "run the pump backwards" hack was working as a temporary workaround that allowed it to work for a short while.

 

[suprasvobodea]

That sounds like a solenoid issue. Have you tried the active test in Techstream that opens and closes it? It keeps it open for about a second and then automatically closes it. You can hear it click. If that doesn't work you could apply 12V directly and see if that does it, combined with forcing the pump to run.
Considering you had debris in the return valve, it is possible that there might be a contamination in the system that affects the solenoids.

My huge Impex order is as the customs and I am anxious to see what is going on with my AHC. The return valve by itself sounds super promising, as I am facing the same issue as you, weak stream and all. Maybe my "run the pump backwards" hack was working as a temporary workaround that allowed it to work for a short while.

<UPDATE>. 7/22
Oridingbg- I did run the ACTIVE test on the Techstream dashboard after I got the engine running but did not press the UP or DOWN switch to trigger 1762. That's the only way to get the system to work! I went through all the tests. The SL FG and SLFL both went ON and then showed OFF. The SLRL & SLRG - only the SLGL turned ON briefly, but the SLRL would not. I'll double recheck these rears,, I want to make sure I didn't get these two rears - mixed up on which worked and which didn't.

Since the return valve was plugged up, after removing it, putting a brake cleaner tube in the end, and blowing it out, it works! How do I test the CONTROL VALVE Assy?

 

[wrigh003]

Man I’d love to help but all I did with mine was bleed through the bleed screws with power/ suction instead of just gravity. If there’s not fluid back there and/ or a solenoid isn’t opening to let fluid back then sadly that’s beyond me.

 

[suprasvobodea]

I am not getting ANY fluid to the rear globes to even try to bleed!! Something is wrong.... but I don't have the experience to know what to do next.? INDOcRUISE .- what should I check next? Im running outta time. I need to get this running by Wednesday so I can drive 1000 miles up to Wisconsin!!

UPDATE 7-21- INDOCRUISE
To clarify and simplify I have replied in BLUE above

I am not getting ANY fluid to the rear globes to even try to bleed!! Something is wrong.... but I don't have the experience to know what to do next.? INDOcRUISE .- what should I check next? Im running outta time. I need to get this running by Wednesday so I can drive 1000 miles up to Wisconsin!!

UPDATE 7-21- INDOCRUISE
To clarify and simplify I have replied in BLUE above

GOOD NEW UPDATES 7/26 >>>>

I did some more testing and have new updates. ( with pictures of Techstream and my LX. I did the ACTIVE TEST from Techstream's dashboard and posted the results below.

This is the FIRST TIME in 5 months that the FRONT globe has held pressure and the height indicators are POSTIVE! The pressure on the front is good as well. (11.0) I tested the 4 Gate and Level valves ( SLRL, SLRG, SLFL, SLFG) The results are as follows: Both front SLFL, and SLFG did switch from OFF to ON momentarily - which makes sense since the fronts have pressure and the truck lifted 3.5" !! However, the REAR pressure would not increase and the rear did not raise as all. ( See photo)

That is my LX which now has the Front at normal height and the rear on the bump stops. The Issue seems to be the REAR SLRL - the rear lift valve is not getting a signal to open. So I disconnected the connector and tested the continuity of both the connector and the control valve body itself. ( See photo)

I got continuity from #2 >> to 1,3,4,5. I tried to check continuity from the connector from the Control valve through the wire harness to the AHC computer, especially the RHL lead on the control valve (#5) B-O wire >> AHC connector (#21 B-O) wire but I didn't have a small pin to stick in the AHC connector. However, in the previous test, I checked #2 on the control valve to the other 4 pins, and all showed continuity. This leads me to the last question, and maybe the final, unanswered question as to WHY the ACTIVE SLRL test I did with Techstream, did NOT WORK?!?!?!? I NEED THE ANSWER TO THIS TO FINALLY GET TO THE 1762 CODE CONSTANTLY RETURNING.

Indocruise, or anyone on this, what do you think I should check out next??

<<<<< EDIT>>>> 7/26 7:30 PM CST
I just developed a NEW code, 1731 which the TSM says is a FRONT Lift valve. I tried repeatedly to delete with both tech stream and doing the jumper system in the engine bay, and it WOULD NOT DELETE. I then checked the description and it mentions B+ <10 V it will trigger the "fail safe" system .
When I checked the Volts at pins #13 (W-L) and #22 (W-B) it supposed to be 11-14V and mine is just 1.7 and slowly drained down to 0.2 V . My question is , WHAT IS B+ VOLTAGE AND WHERE DOES IT COME FROM ON THE ACH COMPUTER?

 

[Moridinbg]

I didn't understand, did the SLRL & SLRG switch with the Active test or not? If they did not - use a piece of wire or a paperclip to stick in the AHC plug and check continuity.

• If you don't have continuity - BD1/2 are notorious for corroding inside the plug. They are in a super sh1tty place too.
• If you have continuity - apply power directly to the solenoid pins on the control valve and see if it will switch.
  • If it doesn't switch - bad control valve assembly
  • If it does switch and you have continuity - bad AHC ECU

 

[IndroCruise]

I acknowledge the greater depth of knowledge and extensive hands-on experience of @Moridinbg -- very few people have undertaken and survived the back-to-basics re-build and subsequent running repairs around Europe and all over South America to anything like the same extent! I concur with his assessments above in Post #149 and Post #153. The nature and locations of the mentioned (and infamous and problematic) BI1 and BI2 connectors are shown on the attachments -- and problems here also have been reported extensively by @suprarx7nut and @2001LC in other threads. "Problems" means not just cleaning dirty connectors but also testing and confirming continuity from those connectors at least back to the next connector -- and really, all the way to the ECU.

Given the experience with the highly unusual blockage in the Return Valve (due in my opinion to returning fluid as explained in my Post #141), it would not be surprising if there was a similar blockage within a solenoid-operated Levelling Valve, caused by returning fluid in a similar way -- even though new 'globes' and new 'shock absorbers' have been fitted to this vehicle.

For this reason, if this were my vehicle, I would first persist with the attempting to open the Rear Levelling Valve by powering it in the manner described by @Moridinbg (now having given up on trying to force fluid past the Rear Levelling Valve while it is closed), and then run the AHC Pump with direct 12 volt supply, with at least one Rear bleeder screw open -- otherwise much as described in Post #132 and Post #145. The purpose of this exercise is to attempt to flush AHC Fluid through the Levelling Valve in the hope of dislodging a possible blockage on the "wheel side" of the Levelling Valve.

If this does not overcome the problem, I would then be inclined to pursue the electrical diagnosis highlighted by @Moridinbg.

I might be inclined to experiment further -- and explore disassembly and internal cleaning of the Control Valve Assembly -- although replacement with a second-hand unit might be more expedient.

The coloured Electrical Wiring Diagram (EWD) may be of assistance in tracing the relevant circuits. By the way, please note that the circuit for the Rear Height Control Sensor also passes through the BI1 connector and loss of continuity here can be a cause of aberrant behaviour of the AHC system.

 

[suprarx7nut]

GOOD NEW UPDATES 7/26 >>>>

I did some more testing and have new updates. ( with pictures of Techstream and my LX. I did the ACTIVE TEST from Techstream's dashboard and posted the results below. View attachment 3686965

This is the FIRST TIME in 5 months that the FRONT globe has held pressure and the height indicators are POSTIVE! The pressure on the front is good as well. (11.0) I tested the 4 Gate and Level valves ( SLRL, SLRG, SLFL, SLFG) The results are as follows: Both front SLFL, and SLFG did switch from OFF to ON momentarily - which makes sense since the fronts have pressure and the truck lifted 3.5" !! However, the REAR pressure would not increase and the rear did not raise as all. ( See photo) View attachment 3686966
That is my LX which now has the Front at normal height and the rear on the bump stops. The Issue seems to be the REAR SLRL - the rear lift valve is not getting a signal to open. So I disconnected the connector and tested the continuity of both the connector and the control valve body itself. ( See photo)
View attachment 3687027

View attachment 3687030

I got continuity from #2 >> to 1,3,4,5. I tried to check continuity from the connector from the Control valve through the wire harness to the AHC computer, especially the RHL lead on the control valve (#5) B-O wire >> AHC connector (#21 B-O) wire but I didn't have a small pin to stick in the AHC connector. However, in the previous test I checked #2 on the control valve to the other 4 pins, and all showed continuity . This leads me to the last question, and maybe the final, unanswered question as to WHY the ACTIVE SLRL test I did with Techstream , did NOT WORK?!?!?!? I NEED THE ANSWER TO THIS TO FINALLY GET TO THE 1762 CODE CONSTANTLY RETURNING.

Indocruise, or anyone on this, what do you think I should check out next??

Great update. Pictures are helpful.

My approach, having seen multiple harness faults in this area:

Pull the BI1 connector apart. It's in the rear driver quarter of the frame. It can help to spray those connectors down with water to clean off dried dirt. You should measure the continuity checks from there. You don't need to measure towards the ECU. The ECUs are essentially bulletproof. The wiring in this area is the complete opposite.

You should get all the same measurements from BI1 to the solenoid as what you measured right on the control valve. If not, there's your issue. I repaired a customers car by running a new lead from the connector at BI1 (or perhaps the other big one right there) straight to the height control accumulator. The harness in between had shorted to ground and was causing problems, including code 1762. He checked back in a year or so after the repair and all was still well.

If the wiring doesn't show any problems, then I'd apply power manually and force that valve to actuate. Perhaps it just needs to flick on and off a bunch to clear a bit of debris.

 

[suprasvobodea]

I acknowledge the greater depth of knowledge and extensive hands-on experience of @Moridinbg -- very few people have undertaken and survived the back-to-basics re-build and subsequent running repairs around Europe and all over South America to anything like the same extent! I concur with his assessments above in Post #149 and Post #153. The nature and locations of the mentioned (and infamous and problematic) BI1 and BI2 connectors are shown on the attachments -- and problems here also have been reported extensively by @suprarx7nut and @2001LC in other threads. "Problems" means not just cleaning dirty connectors but also testing and confirming continuity from those connectors at least back to the next connector -- and really, all the way to the ECU.

Given the experience with the highly unusual blockage in the Return Valve (due in my opinion to returning fluid as explained in my Post #141), it would not be surprising if there was a similar blockage within a solenoid-operated Levelling Valve, caused by returning fluid in a similar way -- even though new 'globes' and new 'shock absorbers' have been fitted to this vehicle.

For this reason, if this were my vehicle, I would first persist with the attempting to open the Rear Levelling Valve by powering it in the manner described by @Moridinbg (now having given up on trying to force fluid past the Rear Levelling Valve while it is closed), and then run the AHC Pump with direct 12 volt supply, with at least one Rear bleeder screw open -- otherwise much as described in Post #132 and Post #145. The purpose of this exercise is to attempt to flush AHC Fluid through the Levelling Valve in the hope of dislodging a possible blockage on the "wheel side" of the Levelling Valve.

If this does not overcome the problem, I would then be inclined to pursue the electrical diagnosis highlighted by @Moridinbg.

I might be inclined to experiment further -- and explore disassembly and internal cleaning of the Control Valve Assembly -- although replacement with a second-hand unit might be more expedient.

The coloured Electrical Wiring Diagram (EWD) may be of assistance in tracing the relevant circuits. By the way, please note that the circuit for the Rear Height Control Sensor also passes through the BI1 connector and loss of continuity here can be a cause of aberrant behaviour of the AHC system.

View attachment 3687404

UPDATE << 7/27>> 11:30

I just had a NEW issue and it's with the B+ signal on Techstream. It's Way low, @ 1.7 V !! Where does B+ V come from and should I check the AHC computer connector S6 pins? If so,... Which PINs do I check ? Any voltage < 10.0 V WILL cause an error code 1731 - which is a fail-safe for the front leveling valve. This was JUST working yesterday!! Geez............ I'm going backward now....!

 

[Moridinbg]

Low B+ is pretty much 100% sign for wiring harness issues. I have seen it as a symptom in many failed AHC issues and it always was caused by broken wire or corroded plug.
My bad, BI1/2 are the easiest to access, they are under the rear bumper. The BDs between the frame and body, right next to the wheel, are the hard to access ones.
Anyway, check continuity from ECU to valve assembly, then ECU to BI and BI to valve assembly, somewhere along the way you should find the problem.

 

[suprasvobodea]

Great update. Pictures are helpful.

My approach, having seen multiple harness faults in this area:

Pull the BI1 connector apart. It's in the rear driver quarter of the frame. It can help to spray those connectors down with water to clean off dried dirt. You should measure the continuity checks from there. You don't need to measure towards the ECU. The ECUs are essentially bulletproof. The wiring in this area is the complete opposite.

You should get all the same measurements from BI1 to the solenoid as what you measured right on the control valve. If not, there's your issue. I repaired a customers car by running a new lead from the connector at BI1 (or perhaps the other big one right there) straight to the height control accumulator. The harness in between had shorted to ground and was causing problems, including code 1762. He checked back in a year or so after the repair and all was still well.

View attachment 3687456

If the wiring doesn't show any problems, then I'd apply power manually and force that valve to actuate. Perhaps it just needs to flick on and off a bunch to clear a bit of debris.

SupraRXnut:

So you are saying I disconnect the Bl1 back by the bumper and check the 4 wires at the Bl1 >> to the solenoid ( basically testing impedance THRU the BD2 connector > to the corresponding pin on the disconnected control valve 5 pin connector I show in the picture in post #152? is that correct? I also realized fro the wiring diagram that B+ is the output of the main AHC relay!!! So I am going back outside to test this relay - again. It was working, but that output feeds right into B+ on the AHC control computer pin #13. "I'll BE BAAAAAACK !

 

[suprasvobodea]

That sounds like a solenoid issue. Have you tried the active test in Techstream that opens and closes it? It keeps it open for about a second and then automatically closes it. You can hear it click. If that doesn't work you could apply 12V directly and see if that does it, combined with forcing the pump to run.
Considering you had debris in the return valve, it is possible that there might be a contamination in the system that affects the solenoids.

My huge Impex order is as the customs and I am anxious to see what is going on with my AHC. The return valve by itself sounds super promising, as I am facing the same issue as you, weak stream and all. Maybe my "run the pump backwards" hack was working as a temporary workaround that allowed it to work for a short while

UPDATE >> **Moridinbg>>

When I use the ACTIVE TEST in Techstream, I can get the Front Gate and Front Level functions to switch to ON momentarily like they should. However, when I try to get the Rear Level and Gate functions to switch on, it does not work right away. It takes 4-6 pushes on that little arrow in the window to trigger them to ON. And when they do switch ON momentarily, I CANNOT get them to repeat it after the 1st time! I have to close out the window and re-open that specific test and it takes 4-7 pushes on the arrow to make it work. So . what does that mean ?? I DID get all 4 globes to pressurize, and hold. but after 5 min or so when I pressed the UP button again,,it just started to lose pressure and drop back down again, and it won't go up again. Im still getting 1762 and repeatedly clear it in Techstream. I also got the rear globes to pressurize the first time. There was a little oil in the accumulator. which I bleed too. I will check the impedance from the control valve wire harness connector back to Bl1 next.

 

[suprasvobodea]

Great update. Pictures are helpful.

My approach, having seen multiple harness faults in this area:

Pull the BI1 connector apart. It's in the rear driver quarter of the frame. It can help to spray those connectors down with water to clean off dried dirt. You should measure the continuity checks from there. You don't need to measure towards the ECU. The ECUs are essentially bulletproof. The wiring in this area is the complete opposite.

You should get all the same measurements from BI1 to the solenoid as what you measured right on the control valve. ( WHat do You mean .."You should get the same Ohm reading right at control valve ! " What do i measure at the control valve??? I dont know what I am suppsoe to check on the control valve ?!? If not, there's your issue. I repaired a customers car by running a new lead from the connector at BI1 (or perhaps the other big one right there) straight to the height control accumulator. The harness in between had shorted to ground and was causing problems, including code 1762. He checked back in a year or so after the repair and all was still well.

View attachment 3687456

If the wiring doesn't show any problems, then I'd apply power manually and force that valve to actuate. Perhaps it just needs to flick on and off a bunch to clear a bit of debris.

UPDATE >. 7/27 ( See my replies in BLUE above