Groaning sound coming from AHC 2002 Lexus LX 470.

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Howdy folks,

So, I have been having some issues with my AHC recently and I just had the truck serviced at the Lexus dealer when I was visiting my folks over the Thanksgiving weekend where they replaced a wire harness that had ben ruined(the AHC had been stuck in normal for several months and I had tried to download TechStream and in the process I bricked a perfectly good laptop so I took the truck to my local Toyota dealer but they couldn't get into the AHC software)and the AHC worked fine for a few days but it has gotten very cold here and now the truck seems to struggle staying in Normal and won't go into high.

Occasionally when it is trying to adjust on it's own when I leave the truck idle in my garage or in my driveway I hear a groaning sound that sounds like metal rubbing against metal the way a hydraulic jack might sound if it had been sitting for a long time outside.

I have tried searching for what the source of this sound would be and I am busy on PartsSouq trying to figure out which parts would make a sound like that and I am just not sure. It sounds like it's coming from the passenger side but I can never get under there quick enough to see if I can narrow it down.

There must be some sort of hydraulic ram on these but I am too dumb to know which part.

Any insight as to what I should try focusing my attention to?
 

suprarx7nut

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Groaning sound is tough to pinpoint by description alone. Any chance you can snag a video showing this sound?

AHC moves the suspension around. Could be any number of joints.

AHC will fail to go into H or even hold N height if the pressures aren't in spec. This is common on vehicles that have been neglected (pressures never checked or adjusted). The fix is quick and easy (often free) once you get yourself connected to Techstream or another scan tool that shows AHC pressures.
 
Joined
Jul 7, 2016
Messages
3,071
Location
Twin Ports of Superior, WI and Duluth, MN
Groaning sound is tough to pinpoint by description alone. Any chance you can snag a video showing this sound?

AHC moves the suspension around. Could be any number of joints.

AHC will fail to go into H or even hold N height if the pressures aren't in spec. This is common on vehicles that have been neglected (pressures never checked or adjusted). The fix is quick and easy (often free) once you get yourself connected to Techstream or another scan tool that shows AHC pressures.
Yeah, I am going to have to try to download TechStream again without using the disc I bought online along with the cable. The nearest Lexus dealer is several hours away and nobody in my area can get into the AHC data.

I do know everything was working right two weeks ago after I had it serviced. I also know the fluid was changed about 20K ago. This seems to be related to it being cold.

I will see if I can post a video of it but the sound is intermittent.

Is there any parts that I could try lubing to see if it would go away and help narrow down what may need attention?

I realize that what I am asking for is not the ideal way to address this issue but I am limited a bit due to geography. I also have the full printed version of the FSM for this truck if anyone is familiar with where I could look in there to help diagnose the issue.
 
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Brisbane, Australia
Yeah, I am going to have to try to download TechStream again without using the disc I bought online along with the cable. The nearest Lexus dealer is several hours away and nobody in my area can get into the AHC data.

I do know everything was working right two weeks ago after I had it serviced. I also know the fluid was changed about 20K ago. This seems to be related to it being cold.

I will see if I can post a video of it but the sound is intermittent.

Is there any parts that I could try lubing to see if it would go away and help narrow down what may need attention?

I realize that what I am asking for is not the ideal way to address this issue but I am limited a bit due to geography. I also have the full printed version of the FSM for this truck if anyone is familiar with where I could look in there to help diagnose the issue.

It is too early to jump to conclusions without more information but here is something you might try ….

Suggest try dropping the vehicle to “LO” height and then raise to “N”. After pressing the ‘raise’ button, the Height Control Accumulator should open and raise the vehicle reasonably quickly. When raised, the green AHC light in the instrument panel will stop flashing at “N” and the AHC Pump will be heard continuing to operate as it re-charges the Height Control Accumulator, until eventually the AHC Pump is heard to stop.

The point of this exercise is to listen to
  • the AHC Pump – below and behind the AHC Tank, the motor is visible but the pump faces the firewall, all on the passenger side of a LHD vehicle, and,
  • any other noises from movements around the vehicle at this time while the AHC Pump is operating.
Does pump operation seem normal? Or is it struggling? The pump will struggle if AHC pressures are excessive or if the vehicle and contents are overweight (and which adds to AHC pressures). The report “…. truck seems to struggle staying in Normal and won't go into high” does suggest excessive AHC pressures.

If there is no confirmation that AHC pressures actually have been checked (impossible without accessing the Suspension ECU or using pressure gauges at the bleeder valves – so clearly the Dealer has not checked AHC pressures), then it is a fair assumption on a 2002 vehicle that the AHC pressures are too high. You could fly blind and test this assumption by making (say) five clockwise turns looking up at both torsion bar adjusters to reduce Front AHC pressures by about 1 Mpa – then seeing whether this makes a difference. This won’t do any damage and can easily be unwound. However, without Techstream or other AHC-capable scanner it is impossible to know whether five turns is enough. (By the way, it is incredible that the Dealer does not have at least a Toyota/Lexus Handheld Tester – which can easily deal with the AHC ECU – but it is common around the world for Dealers not to know what to do with the AHC system!!!).

If the AHC Pump seems normal, then it is time to look at the movements of the mechanical parts of the suspension, and in particular, check ALL rubber bushings throughout the front and rear suspension. You could try hosing all bushings with water to see whether that reduces the noise -- water lubricates rubber.

On the question about where to look in the FSM, the following may help …..

The Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) are common to LX470 and to some models of LC100 (where fitted, varies around the world).

Under the skin, the suspension is almost the same across the LC100 and LX470 model range – with some differences in specifications and part numbers of springs and torsion bars in different markets – but no differences in the AHC/TEMS specifications across the range.

The links below relate to the official on-line Factory Service Manual (FSM) for the Toyota Land Cruiser 100 series and 105 series – all models, all years. The FSM does not include Part Numbers.

It is likely that you will be able to find the same sections in the hardcopy LX470 Factory Service Manual if you have all the volumes. If not, here are the relevant parts from the LC100 FSM:

An illustrated General Description of AHC and TEMS can be found by following the tabs mentioned within the link below. This 20 page item is well-illustrated with diagrams and explanations of the function of each of the components in the AHC/TEMS system. This helps give a ‘mental picture’ of how it all works. There is no diagnostic nor repair information in this section.

LC100 Workshop Manual - https://lc100e.github.io/
then use tabs at LHS of opening page
+ New Car Features
+ CHASSIS
+ Suspension
+ Active Height Control Suspension and Skyhook TEMS

AHC and TEMS Diagnostics information is found here -- but Techstream is necessary to go beyond physical symptoms:

LC100 Workshop Manual - https://lc100e.github.io/
then use tabs at LHS of opening page
+ Repair Manual
+ DIAGNOSTICS
+ ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS

Repair and Specification Details are found here:

LC100 Workshop Manual - https://lc100e.github.io/
then use tabs at LHS of opening page
+ Repair Manual
+ SUSPENSION AND AXLE
This section covers all non-AHC mechanical aspects of the suspension and axle arrangements.

Scrolling down further within this SUSPENSION AND AXLE section reveals the AHC repair and specification information:

+ ACTIVE HEIGHT CONTROL SYSTEM (Independent Front Suspension)
+ ACTIVE HEIGHT CONTROL PUMP & MOTOR (Independent Front Suspension)
+ CONTROL VALVE ASSEMBLY (Independent Front Suspension)
+ HEIGHT CONTROL ACCUMULATOR (Independent Front Suspension)
+ PUMP ATTENUATOR (Independent Front Suspension)
+ DAMPING FORCE CONTROL ACTUATOR (Independent Front Suspension)
+ HEIGHT CONTROL SENSOR (Independent Front Suspension)
 
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It is too early to jump to conclusions without more information but here is something you might try ….

Suggest try dropping the vehicle to “LO” height and then raise to “N”. After pressing the ‘raise’ button, the Height Control Accumulator should open and raise the vehicle reasonably quickly. When raised, the green AHC light in the instrument panel will stop flashing at “N” and the AHC Pump will be heard continuing to operate as it re-charges the Height Control Accumulator, until eventually the AHC Pump is heard to stop.

The point of this exercise is to listen to
  • the AHC Pump – below and behind the AHC Tank, the motor is visible but the pump faces the firewall, all on the passenger side of a LHD vehicle, and,
  • any other noises from movements around the vehicle at this time while the AHC Pump is operating.
Does pump operation seem normal? Or is it struggling? The pump will struggle if AHC pressures are excessive or if the vehicle and contents are overweight (and which adds to AHC pressures). The report “…. truck seems to struggle staying in Normal and won't go into high” does suggest excessive AHC pressures.

If there is no confirmation that AHC pressures actually have been checked (impossible without accessing the Suspension ECU – so clearly the Dealer has not checked AHC pressures), then it is a fair assumption that the AHC pressures are too high. You could fly blind and test this assumption by making (say) five clockwise turns looking up at the torsion bar adjusters to reduce Front AHC pressures by about 1 Mpa – then seeing whether this makes a difference. This won’t do any damage and can easily be unwound. However, without Techstream or other AHC-capable scanner it is impossible to know whether five turns is enough. (By the way, it is incredible that the Dealer does not have at least a Toyota/Lexus Handheld Tester – which can easily deal with the AHC ECU – but it is common around the world for Dealers not to know what to do with the AHC system!!!).

If the AHC Pump seems normal, then it is time to look at the movements of the mechanical parts of the suspension, and in particular, check ALL rubber bushings throughout the front and rear suspension. You could try hosing all bushings with water to see whether that reduces the noise -- water lubricates rubber.

On the question about where to look in the FSM, the following may help …..

The Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS) are common to LX470 and to some models of LC100 (where fitted, varies around the world).

Under the skin, the suspension is almost the same across the LC100 and LX470 model range – with some differences in specifications and part numbers of springs and torsion bars in different markets – but no differences in the AHC/TEMS specifications across the range.

The links below relate to the official on-line Factory Service Manual (FSM) for the Toyota Land Cruiser 100 series and 105 series – all models, all years. The FSM does not include Part Numbers.

It is likely that you will be able to find the same sections in the hardcopy LX470 Factory Service Manual if you have all the volumes. If not, here are the relevant parts from the LC100 FSM:

An illustrated General Description of AHC and TEMS can be found by following the tabs mentioned within the link below. This 20 page item is well-illustrated with diagrams and explanations of the function of each of the components in the AHC/TEMS system. This helps give a ‘mental picture’ of how it all works. There is no diagnostic nor repair information in this section.

LC100 Workshop Manual - https://lc100e.github.io/
then use tabs at LHS of opening page
+ New Car Features
+ CHASSIS
+ Suspension
+ Active Height Control Suspension and Skyhook TEMS

AHC and TEMS Diagnostics information is found here -- but Techstream is necessary to go beyond physical symptoms:

LC100 Workshop Manual - https://lc100e.github.io/
then use tabs at LHS of opening page
+ Repair Manual
+ DIAGNOSTICS
+ ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS

Repair and Specification Details are found here:

LC100 Workshop Manual - https://lc100e.github.io/
then use tabs at LHS of opening page
+ Repair Manual
+ SUSPENSION AND AXLE
This section covers all non-AHC mechanical aspects of the suspension and axle arrangements.

Scrolling down further within this SUSPENSION AND AXLE section reveals the AHC repair and specification information:

+ ACTIVE HEIGHT CONTROL SYSTEM (Independent Front Suspension)
+ ACTIVE HEIGHT CONTROL PUMP & MOTOR (Independent Front Suspension)
+ CONTROL VALVE ASSEMBLY (Independent Front Suspension)
+ HEIGHT CONTROL ACCUMULATOR (Independent Front Suspension)
+ PUMP ATTENUATOR (Independent Front Suspension)
+ DAMPING FORCE CONTROL ACTUATOR (Independent Front Suspension)
+ HEIGHT CONTROL SENSOR (Independent Front Suspension)
Thank you very much for the detailed response! I think I need t o try again to get TechStream running on my laptop or it really does seem like I am flying blind.
 
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Messages
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OK, I finally got Techstream to work and I found some codes.

I also tried moving it up and down and it seems to work fine for right now.

I am wondering about my rear pressures. The front pressure seemed to vary between zero and a high of 11 or so in HIGH setting.

I carry quite a bit of weight as I have the rear seats removed and I have a carpentry business worth of tools in the truck which probably weighs less than 500 pounds and I don't currently have my spare tire mounted.

Do you think I just may need new rear springs or can we ascertain from the data here to suggest a further problem? I am a fairly decent shade tree mechanic but this system is new to me so I appreciate your patience if I sound like a noob. :)

AHC Trouble Code.jpg


AHC.jpg
 

suprarx7nut

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OK, I finally got Techstream to work and I found some codes.

I also tried moving it up and down and it seems to work fine for right now.

I am wondering about my rear pressures. The front pressure seemed to vary between zero and a high of 11 or so in HIGH setting.

I carry quite a bit of weight as I have the rear seats removed and I have a carpentry business worth of tools in the truck which probably weighs less than 500 pounds and I don't currently have my spare tire mounted.

Do you think I just may need new rear springs or can we ascertain from the data here to suggest a further problem? I am a fairly decent shade tree mechanic but this system is new to me so I appreciate your patience if I sound like a noob. :)

View attachment 3190773

View attachment 3190774
Code 1736 is commonly a wiring harness fault between BI1 connector at the rear driver side of frame and the solenoid up towards the driver. Relatively easy fix once you know what wire to check and how to use a multimeter.

The 1764 code is a result of the other code, commonly. It can disregarded right now.

1713 might be related to the same wiring harness fault or it could just be a bad sensor. A little multimeter testing should prove that out.

Good work getting techstream running. You'd never have gotten this info attempting manual troubleshooting unless you were on the extreme expert side of electrical work.

I should get some EWD diagrams posted up on my site for folks that run into these problems. With out the EWD it's extremely tough.
 
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Messages
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Location
Brisbane, Australia
OK, I finally got Techstream to work and I found some codes.

I also tried moving it up and down and it seems to work fine for right now.

I am wondering about my rear pressures. The front pressure seemed to vary between zero and a high of 11 or so in HIGH setting.

I carry quite a bit of weight as I have the rear seats removed and I have a carpentry business worth of tools in the truck which probably weighs less than 500 pounds and I don't currently have my spare tire mounted.

Do you think I just may need new rear springs or can we ascertain from the data here to suggest a further problem? I am a fairly decent shade tree mechanic but this system is new to me so I appreciate your patience if I sound like a noob. :)

View attachment 3190773

View attachment 3190774

Congratulations on getting Techstream running -- that is an achievement in itself!!

Thank you for posting the Techstream screenshots -- it helps to see the whole page, including ALL of the detail in addition to the pressures.

References to useful FSM links can be found in my Post #4 in this current thread, not repeated in this post. May I refer you especially to the "AHC General Description" and the AHC part of the “Diagnostics” section?

Not mentioned in Post #4 but may I also suggest scrolling down to the “Electrical Wiring Diagram” (EWD) section in LC100 Workshop Manual - https://lc100e.github.io/ and exploring your model year there? Be a little wary -- this is an LC100 reference, not an LX470 reference and there can be some differences in detail. However, the Active Height Control (AHC) system and the integrated Toyota Electronic Modulated Suspension (TEMS) are common across “100 series” on all LX470 and LC100 models (where fitted).

This response is too long – caused by a lot of cut-and-past taken from elsewhere!!

Anyway, dealing with some of the issues arising ….

On Diagnostic Trouble Codes (DTC’s) generally:

First, suggest cancel all of the DTC’s using Techstream -- or do this manually by disconnecting and reconnecting the battery -- and see what DTC’s return. The idea is to eliminate any old and irrelevant codes in the ECU memory, ensure current codes are identified, and work from there.

AHC Pressures:

The Front AHC pressure is incredibly low at 0.1Mpa.

The Rear AHC pressure is way high at 10Mpa.

If not already done, suggest do at least three tests to be sure of consistency in the numbers -- allow plenty of time for the AHC Pump to finish its business and become silent well after the green AHC light on the dashboards stops blinking. Then record the screenshot.

Also suggest timing the raise from "LO" to "N" a few times -- (1) timing the interval between raise start and when AHC green light stops flashing on the dashboard (means vehicle is raised), and, (2) timing the interval between when the vehicle is raised (green light stops flashing) and when the AHC Pump stops (means Height Control Accumulator is re-charged) -- this may give a preliminary indication of AHC Pump performance or hint at blockages in the system or other aberrations including harness problems.

Taken together with the reported DTC's C1736 and C1764 and the reported noise, the "AHC Pump" and "harness and connector issues" may have to go on the "list of suspects.

Vehicle Weight and AHC Pressures

The FSM specifies checking AHC pressures with vehicle empty, meaning no passengers, no added load, on a level surface, steering straight ahead (not 173.25 degrees as on the screenshot), fuel tanks full.

All good stuff. The purpose of that specification is to ensure that the AHC pressure checks and consequent adjustments are made with the vehicle in the same ‘standard’ condition every time, so that change (inevitable AHC pressure increase) over time (years) can be observed and so that numbers are comparable with FSM-specified numbers.

The AHC system itself is not adjustable. It is the mechanical part of the suspension which is adjusted or modified to accept more or less permanent load while leaving the AHC system performing the same duty.

As a practical matter,
rather than stick to the FSM 'standard', it works well for AHC-related checks and adjustments to be done on the vehicle carrying whatever load it would mostly carry on a consistent basis. So the weight of persons, load, accessories and fittings does not matter provided the checks and adjustments are done with the vehicle in the same condition every time. You can be in or out of the vehicle but is best to adopt the same procedure every time. Then matters such as torsion bar adjustments and changes to rear springs etc can be made which support the usual condition of the vehicle, and, allow the Front and Rear AHC pressures to be brought within the FSM-specified ranges for best damping performance for the usual condition of the vehicle.

Vehicle Operating Height -- also called ride height -- and AHC Pressures:

More height means increased AHC pressures (and vice versa) and that would have to be compensated later.

Few people use the very finnicky, hard-to-measure FSM height specifications. Instead the approximations of hub-to-fender tape-measurements of 19.75 inches (or 500millimetres) at Front both sides, and, 20.50 inches (or 520 millimetres) at the Rear both sides, have been found to be good enough for most purposes for a stock vehicle. This approximation assumes no chassis or body damage nor unusual wear-and-tear of suspension components, control arms, axles, ball-joints etc.

However, these nominated heights are not essential -- it is up to the Owner to decide on the chosen operating heights (or ride heights) of his/her vehicle, within the allowable limits of the suspension geometry and drivelines.

The point is that vehicle height and AHC pressures are related.

See further comments at my Post #7 at this link:
Factory AHC Sensor Position - https://forum.ih8mud.com/threads/factory-ahc-sensor-position.1297829/#post-14730931

C1713 – Rear Height Control Sensor Circuit (there is only one Rear Sensor):

DTC-related to a Height Control Sensor circuit (C1711, C1712, C1713) indicates a definite problem in this circuit. It might be a circuit/harness problem or a problem with the Sensor itself. The Sensor might respond to dismantling, cleaning and testing, but frankly an original Sensor on this 2002 vehicle is now 20 years old -- it may be best to cut to the chase and replace the Sensor with a new Toyota/Lexus or AISIN part.

Toyota/Lexus Height Control Sensors – Part Numbers:
89405-60012 (Front Right)
89406-60022 (Front Left)
89407-60010 (Rear)

Or consider AISIN Sensors -- because AISIN are suppliers to Toyota/Lexus:

Aisin Height Control Sensors – Part Numbers:
HST-020 (Front Right)
HST-021 (Front Left)
HST-026 (Rear)

If replacing, for reliability suggest avoid the unhappiness with Height Control Sensors which seems to arrive with cheap short-life substitutes, fakes and second-hand items. It is easy to find cheap substitutes on the web but IH8MUD stories about these mostly are unhappy ones.

In such a situation, the ECU may place the AHC/TEMS system into the defined ‘fail safe function’ if the Suspension Electronic Control Unit (ECU) cannot resolve differences in signals coming from the three Height Control Sensors. See “C1713” in the FSM Diagnostics section. Then AHC operation is prohibited. Adaptive damping by TEMS is prohibited. The Front and Rear of the vehicle may arrive at different heights. The Owner is left puzzling about what has happened.

The point of this long part of the story is that the benefits of a healthy AHC and TEMS systems are lost easily if Height Control Sensors are forgotten and not maintained and replaced when necessary. Such requirements are no different to, say, brake or steering components or the components of any other major system on the vehicle.

Some more observations about Height Control Sensors are found in my post #7 at this link:
Factory AHC Sensor Position - https://forum.ih8mud.com/threads/factory-ahc-sensor-position.1297829/#post-14730931

Now the possible bad news – the Sensor readings on Techstream give no reason to suspect problems with the Front Height Control Sensors, so leave them for now.

However ….

Beware -- absence of DTC's C1711, C1712, C1713 does not provide assurance that a Sensor circuit is healthy! It simply means that the signal is within the FSM-specified range (0.3 volts to 4.7 volts) but does not indicate whether the actual signal is correct for the set height position. See link in previous post #4 this thread to “Diagnostics” section of the FSM.

A fault with brushes or the carbon track or effects of moisture ingress, corrosion or whatever may still allow an acceptable voltage signal from the Sensor within the the required range (so no DTC) but cause an incorrect signal for the height of the vehicle and result in aberrant effects.

There are multiple stories on IH8MUD about AHC difficulties and strange vehicle behaviour which come down to faulty Height Control Sensor(s) even though no DTC is given. These Sensors are simple, robust, longlife items -- but they are 'wear items'. Original Sensors have been operating in the tough underbody environment for at least 15 years (2007 vehicles) or maybe up to 24 years (1998 vehicles) and eventually need replacement.

C1736 – Height Control Accumulator Solenoid Circuit:

Faults on the Height Control Accumulator and its solenoid valve are uncommon but be aware of attached Technical Service Bulletin (TSB) CP-3006.

Related wiring harness problems have surfaced in recent times and these are discussed at Post #9 at the link below and in other related posts by @suprarx7nut, @2001LC and others:
AHC done? - https://forum.ih8mud.com/threads/ahc-done.1299423/#post-14719487

There was another real world example today provided by @84bj60 at Post #4:
* Urgent * AHC Front leveling control valve testing - https://forum.ih8mud.com/threads/urgent-ahc-front-leveling-control-valve-testing.1300477/#post-14731576

It is a reminder that all DTC’s showing up on Techstream relate to the circuit and not only a particular device itself.

C1764 – Height Control Accumulator Solenoid Circuit / Pressure Sensor Circuit / Fluid Clog:

As above for C1736 – these may be related circuit problems.

However, as these vehicles age, it also is not surprising that there are an increasing number of experiences with original AHC Pumps which, over time (many years), have developed partial blockages in the internal strainers within the AHC Pump.

Another too-long post with many pictures near the end of Post #16 and observations concerning the AHC Pump -- including related contributions from @Moridinbg, @suprarx7nut and @2001LC and others -- can be found at this link:

Rear Coil Springs for additional weight, reduction of Rear AHC load and pressures:

LHD vehicles with AHC have a longer LHS rear coil spring whereas RHD vehicles with AHC have the same length on both sides. Apparently the reason for the longer LHS rear coil spring in LHD vehicles is to provide a little more preload to compensate for driver and fuel being weighted more to the left hand side in LHD vehicles.

Many IH8MUD members with AHC on LHD vehicles and with AHC on RHD vehicles replace/upgrade their OEM rear coil springs with the stronger KING KTRS-79 springs (higher spring rate: OEM are about 95 pounds per inch of deflection whereas KING KTRS-79 are about 130 pounds per inch of deflection).

The KING KTRS-79 coils springs are manufactured in Australia -- sometimes bought direct from the manufacturer or from various distributors and eBay sellers in other countries

These springs are packaged in pairs with both springs of equal length.

Some LHD owners add a small spacer (10mm?) on the LHS when installing KING KTRS-79 rear coil springs.

An alternative to upgraded springs would be to install airbags in the existing coils which can provide assistance when occasional heavy loads are carried or towed. However, if the loads are constant, the existing OEM springs are lightweight and would be 20 years old in your 2002 vehicle, and so upgraded rear coil springs may be the best bet.

Anyway, all of the above must be enough to think about for one day under the shade tree!!
 

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Hi again folks,

So, I thought everything was working as it should after my last effort using Tech Stream until this morning. It's pretty cold here again (-5F) and the rear is dropped again. The front appears to be normal and the light says I am in Normal. I can get the front to go up and down but the rear won't budge or if it does, it's barely perceptible.

I don't have time this morning to get back into Tech Stream but I am hoping this new information along with what I have provided could give you guys a better idea of what I need to be looking at. I do believe that whatever is happening in the rear is related to colder temps as the truck was fine this weekend when the temps were in the upper 20s-low 30s but as soon as it gets colder than say 15 degrees F, the rear acts up. This is just the beginning of our winter and it gets down to -35 occasionally without the wind. I keep the truck in an unheated garage that is still warmer than the outside temps, but not warm enough to "thaw" whatever is giving me grief.

Any further thoughts?
 
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Messages
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Hi again folks,

So, I thought everything was working as it should after my last effort using Tech Stream until this morning. It's pretty cold here again (-5F) and the rear is dropped again. The front appears to be normal and the light says I am in Normal. I can get the front to go up and down but the rear won't budge or if it does, it's barely perceptible.

I don't have time this morning to get back into Tech Stream but I am hoping this new information along with what I have provided could give you guys a better idea of what I need to be looking at. I do believe that whatever is happening in the rear is related to colder temps as the truck was fine this weekend when the temps were in the upper 20s-low 30s but as soon as it gets colder than say 15 degrees F, the rear acts up. This is just the beginning of our winter and it gets down to -35 occasionally without the wind. I keep the truck in an unheated garage that is still warmer than the outside temps, but not warm enough to "thaw" whatever is giving me grief.

Any further thoughts?

I live in a part of the world where “cold” means around 15 degrees Celsius (59 degrees Fahrenheit)!!!

Therefore it seems best if I leave comments about the effects of seriously cold weather to those who know best.

Maybe I would hazard a guess that the kinds of effects described in previous posts in this thread are made worse if cold temperature contractions of metallic wiring, connectors and other parts increases the gaps in any circuit breaks or looseness – but I think you need more than a guess!
 
Joined
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Messages
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I live in a part of the world where “cold” means around 15 degrees Celsius (59 degrees Fahrenheit)!!!

Therefore it seems best if I leave comments about the effects of seriously cold weather to those who know best.

Maybe I would hazard a guess that the kinds of effects described in previous posts in this thread are made worse if cold temperature contractions of metallic wiring, connectors and other parts increases the gaps in any circuit breaks or looseness – but I think you need more than a guess!
So, I do have an update. I decided that I would try using a hair dryer to warm up the rear sensor and sure enough, it started working again. I think water must have gotten into the wiring housing and was freezing in there and causing it do not be able to make the connection that needs to happen inside that housing. Once it warms up a little and I get back from my holiday trip, I am going to take it apart and see if I can't get it sealed back up. I think I may just try using a little FPIG that I have left over from when I did the head gasket on my 80 and see if that takes care of it.

Thanks again for all of your help!
 

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So, I do have an update. I decided that I would try using a hair dryer to warm up the rear sensor and sure enough, it started working again. I think water must have gotten into the wiring housing and was freezing in there and causing it do not be able to make the connection that needs to happen inside that housing. Once it warms up a little and I get back from my holiday trip, I am going to take it apart and see if I can't get it sealed back up. I think I may just try using a little FPIG that I have left over from when I did the head gasket on my 80 and see if that takes care of it.

Thanks again for all of your help!
Based on my own experience working with carbon trace parts like those sensors and the experience of others on here I've read, I would put the chances of you opening, repairing and reassembling that sensor in a way that make it work reliably riiiiiiight about at zero. No offense at all to your electrical/mechanical skills. :)

I'd plan on a new OEM sensor (absolutely not any aftermarket aside from Denso, but ideally genuine Toyota/Lexus).
 
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Based on my own experience working with carbon trace parts like those sensors and the experience of others on here I've read, I would put the chances of you opening, repairing and reassembling that sensor in a way that make it work reliably riiiiiiight about at zero. No offense at all to your electrical/mechanical skills. :)

I'd plan on a new OEM sensor (absolutely not any aftermarket aside from Denso, but ideally genuine Toyota/Lexus).

Strongly agree with @suprarx7nut -- although I suspect that he may mean "Aisin" rather than "Denso"?? "Aisin" is a Japanese supplier of these kinds of parts to Toyota/Lexus. See also Height Control Sensor recommendations and Part Numbers about half way through Post #8 in this thread.
 

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Strongly agree with @suprarx7nut -- although I suspect that he may mean "Aisin" rather than "Denso"?? "Aisin" is a Japanese supplier of these kinds of parts to Toyota/Lexus. See also Height Control Sensor recommendations and Part Numbers about half way through Post #8 in this thread.
That could be. I thought I had seen folks getting Denso sensors on Rock Auto. Might be Aisin. Either way, I'd avoid even those and buy these straight from a Genuine Toyota/Lexus dealer like McGeorge/Partsouq.
 
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That could be. I thought I had seen folks getting Denso sensors on Rock Auto. Might be Aisin. Either way, I'd avoid even those and buy these straight from a Genuine Toyota/Lexus dealer like McGeorge/Partsouq.
Agreed.
 
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That is great advice. I will plan on getting a new sensor. I can get them from the UAE for around $225 plus shipping. I may take a flyer on Rock Auto as I think I have a credit with them for some parts I returned for a friend's Camry. Denso and Aisin are usually good OEM alternatives but if they are known to be duds, I will just go OEM.

Everything that has happened with the exception of the wiring harness that the Lexus dealer replaced to get the system working again(also the source of the codes I found on TechStream) points to water getting into something that doesn't want to be wet getting wet and when the temps drop this low, the tiny bit of water that gets frozen probably botches the ability of the system to function as it should.

I truly appreciate everyone's advice and help on this as this was the one system that gave me pause when choosing between the Lexus and the Land Cruiser. I really do prefer the ride quality of this system but there is definitely a bit of a learning curve as to how it all works and I am very much still learning just the basics.
 
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That could be. I thought I had seen folks getting Denso sensors on Rock Auto. Might be Aisin. Either way, I'd avoid even those and buy these straight from a Genuine Toyota/Lexus dealer like McGeorge/Partsouq.
Partsouq was $200 less than McGeorge as a reference point for anyone that needs one of these. My local Toyota dealer gives me around 20% off "list" and doesn't charge me shipping but their prices are usually closer to McGeorge, minus the deal I worked out with them because I bought thousands of dollars worth stuff from them when I rehabbed my 80. They don't really "do" Lexus stuff though and this is just one of things that the shipping doesn't kill you to have shipped from the UAE.

Rock Auto was at $188 plus shipping for Aisin.

Always good to have more than iron in the fire. :)
 
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What’s the part number
8940760010SENSOR SUB-ASSY, HEIGHT CONTROL, REARToyota1226.45$


I just copied this off the order on Partsouq. Shipping to me will be less than $14 and it will likely be wrapped in like a half a roll of tape. I picture them throwing the packages on the plane as it takes off because it's astonishing how fast the stuff comes to my fairly remote part of the world that is a long way from where it comes from. It's a miracle of logistics, I can say that much.
 
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8940760010SENSOR SUB-ASSY, HEIGHT CONTROL, REARToyota1226.45$


I just copied this off the order on Partsouq. Shipping to me will be less than $14 and it will likely be wrapped in like a half a roll of tape. I picture them throwing the packages on the plane as it takes off because it's astonishing how fast the stuff comes to my fairly remote part of the world that is a long way from where it comes from. It's a miracle of logistics, I can say that much.

The Part Numbers for Height Control Sensors listed back at Post #8 in this thread are the same for Lexus LX470 and Toyota LC100 (where AHC is fitted).

Here is another little snippet illustrating how the Toyota/Lexus supply chain is helped by cross-shareholdings between Toyota/Lexus and their suppliers – and vice versa. They each own a piece of each other!! See Post #208 at this link:


This is unsurprising. Of the thousands of Parts in a 100 series vehicle (or any Toyota or Lexus vehicle), Toyota/Lexus makes only some of them. "Genuine Part" means a Part controlled by Toyota/Lexus but does not necessarily mean that it actually was manufactured by Toyota/Lexus

When the the Rear Height Control Sensor (Part Number 89407-60010) ordered by @Red Merle arrives, it would be interesting know how the package is marked and what actual manufacturer is stamped on the actual item?

Main message remains unchanged: Stay with reputable suppliers.

Post #1 at the link below provides an example of the reason why (in this case referring to a water pump story):

 

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