Hi All,
Firstly, apologies in advance for this long post. It attempts to describe a current issue as clearly as possible.
I have a longstanding and worsening AHC problem. Help is requested please from anywhere in the world ….
Despite refurbishments which have included lots of vital new parts, the AHC system on my 2006 LC100 steadfastly refuses to rise to any occasion from “LO” to “N” in anything much less than 38 seconds – after having dropped slowly from “N” to “LO” in 22 seconds.
And yet this vehicle will spring from “N” to “HI” in about 14 seconds on command – and then it is happy to drop back to “N” from “HI” in 8 seconds when required.
The Good Book (FSM) says that upwards movements “LO” to “N” or “N” to “HI” should each take about 15 seconds for a healthy system which has been correctly adjusted and is free of excess weight and other interferences and problems. Downwards movements should take 8 seconds or less.
In addition, the vehicle is erratic and does not settle reliably at the same expected front and rear hub-to-fender heights after an up or down movement or after a road trip.
It does not matter what adjustment I make to the Height Control Sensor adjusters, the vehicle resolutely insists on stopping at “N” from “LO” with Techstream (actually ELMscan327) readings of negative 4 to negative 8 millimetres – nowhere near zero!! It is different and a little better when dropping from “HI” to “N”. It is different again, sometimes with positive readings after returning home from a trip. Then, hub-to-fender distances also become a little higher, often half-inch or a little more, which must mean higher but immeasurable AHC pressures, guessing around 1.1 Mpa additional at the front.
The vehicle does maintain reliable and equal ‘cross level’ hub-to-fender distances within one-eighth of an inch (3 millimetres).
Shortly, my vehicle (see signature line) shortly will leave home on the East Coast of Australia and will be delivered to family members in Perth, Western Australia – about 4,300 kilometres (2,680 miles) away.
Naturally, I do not wish to hand over a ‘lemon’. Many very conservative and pre-emptive refurbishments have been undertaken. Some of these replacements of all new Toyota parts were made pre-emptively for longevity and reliability reasons rather than due to other specific adverse ‘symptoms’ -- in particular because it is easy in Australia to get good help on all Landcruiser matters except the mysteries of AHC/TEMS!! It was time for replacement of ‘globes’ and springs. It also was hoped that most issues also would be resolved by these efforts – but this has not happened. The above behaviour prevails even with some very new parts.
Specific details of the vehicle and suspension status include:
The vehicle sits a little low in these tests – raising the vehicle by pushing all Sensor adjusters up their slides has not improved the situation. Nor have attempts to bring the Sensor read-outs closer to zero where they should be. Instead the vehicle was raised and the negative Sensor readings persisted.
The second attachment shows “stills” from a video I made of the on-screen pressure changes during a “LO” to “N” rise of the vehicle. The videos were made as part of an effort to understand what the Levelling Valves in the Control Valve Assembly were doing and also, if possible, to confirm the operation of the solenoid valve on the Height Control Accumulator. (I am not sure what to make of the trace of the Height Control Accumulator pressure). The video file is too big to attach but the marked-up “stills” give the idea. They show the long response times and slow build-up of pressure. These solenoid valves in the Control Valve Assembly and the Height Control Accumulator have been checked by touch and sound and by the “Active Test” and do seem to be operating. Arthritic fingers have not yet succeeded in removing the electrical connectors and so resistances have not yet been checked per FSM, nor has continuity been checked through to the ECU. The new Height Control Sensors all operate correctly. Hopefully there are no blockages in the tiny filter “socks” inside the new AHC Pump! Underbody condition is excellent with no corrosion and no visible harness damage.
I have wondered whether there is mechanical interference somewhere, such as in the suspension bushings or between the airbags and their covers and the rear springs, when moving between “LO” and “N”. My Independent Mechanic thinks not. It all seems to work very well between “N” and “HI”.
Anyway, this is a long story with a lot of attached detail. All advice, comments, critique, ideas from anyone anywhere about what to do next would be most welcome. May I specifically tag @uHu, @PADDO, @LndXrsr, @Moridinbg, @2001LC, @suprarx7nut, whose insights on such matters always has been helpful.
Firstly, apologies in advance for this long post. It attempts to describe a current issue as clearly as possible.
I have a longstanding and worsening AHC problem. Help is requested please from anywhere in the world ….
Despite refurbishments which have included lots of vital new parts, the AHC system on my 2006 LC100 steadfastly refuses to rise to any occasion from “LO” to “N” in anything much less than 38 seconds – after having dropped slowly from “N” to “LO” in 22 seconds.
And yet this vehicle will spring from “N” to “HI” in about 14 seconds on command – and then it is happy to drop back to “N” from “HI” in 8 seconds when required.
The Good Book (FSM) says that upwards movements “LO” to “N” or “N” to “HI” should each take about 15 seconds for a healthy system which has been correctly adjusted and is free of excess weight and other interferences and problems. Downwards movements should take 8 seconds or less.
In addition, the vehicle is erratic and does not settle reliably at the same expected front and rear hub-to-fender heights after an up or down movement or after a road trip.
It does not matter what adjustment I make to the Height Control Sensor adjusters, the vehicle resolutely insists on stopping at “N” from “LO” with Techstream (actually ELMscan327) readings of negative 4 to negative 8 millimetres – nowhere near zero!! It is different and a little better when dropping from “HI” to “N”. It is different again, sometimes with positive readings after returning home from a trip. Then, hub-to-fender distances also become a little higher, often half-inch or a little more, which must mean higher but immeasurable AHC pressures, guessing around 1.1 Mpa additional at the front.
The vehicle does maintain reliable and equal ‘cross level’ hub-to-fender distances within one-eighth of an inch (3 millimetres).
Shortly, my vehicle (see signature line) shortly will leave home on the East Coast of Australia and will be delivered to family members in Perth, Western Australia – about 4,300 kilometres (2,680 miles) away.
Naturally, I do not wish to hand over a ‘lemon’. Many very conservative and pre-emptive refurbishments have been undertaken. Some of these replacements of all new Toyota parts were made pre-emptively for longevity and reliability reasons rather than due to other specific adverse ‘symptoms’ -- in particular because it is easy in Australia to get good help on all Landcruiser matters except the mysteries of AHC/TEMS!! It was time for replacement of ‘globes’ and springs. It also was hoped that most issues also would be resolved by these efforts – but this has not happened. The above behaviour prevails even with some very new parts.
Specific details of the vehicle and suspension status include:
- Vehicle Age and mileage: built 06/2006, travelled 209,652 kilometres (130,271 miles),
- Model: HDJ100R-GNAEZQ “Sahara”, with 1HD-FTE turbodiesel, AHC/TEMS, ABS, A-TRAC, VSC, VGRS,
- Location: Brisbane, Australia,
- ‘Globes’: replaced 05/2019 (new Toyota parts), still showing today ~14 graduations at AHC Tank between “LO” and “HI”,
- FR, FL, and Rear Height Control Sensors: all replaced 07/2020 (new Toyota parts),
- AHC Pump Assembly (pump, motor, pressure and temperature sensors, tank): replaced 10/2020, (new Toyota parts),
- AHC Height Control Accumulator (long cylinder, includes new solenoid valve): replaced 10/2020 (new Toyota part),
- Front Suspension: ‘Sweaty’ Front ‘Shock Absorbers’ replaced 09/2016 (new Toyota parts), original Torsion Bars adjusted to correct Front AHC pressures, front wheel bearings replaced and bushes reviewed 05/2020, steering rack reconditioned 09/2019,
- Rear Suspension: Installed KING KTRS-79 Springs (no spacers) with Firestone airbag assist including Kevlar protectors inside coils 10/2019, also did small Rear Sensor Lift to partially offset low AHC pressures resulting from the higher spring rate of the new springs, also replaced rear LCA’s and rear UCA’s 09/2019,
- Last AHC Fluid change: 10/2020 (new genuine Toyota AHC Fluid 08886-01805),
- ARB Deluxe Front Bar with hoops (no winch) per avatar, KAYMAR single wheel carrier (not full bar), Toyota towbar,
- BFG 275/65R17 KO2 tyres, Load Rating “E”, set at 40 psi for highway cruising,
- Ride Quality and Comfort: Very Good – as expected, slightly firmer than stock especially when empty, due to choice of tyres and rear springs – but excellent when loaded for touring. Excellent response to COMFORT>>SPORT switch settings.
The vehicle sits a little low in these tests – raising the vehicle by pushing all Sensor adjusters up their slides has not improved the situation. Nor have attempts to bring the Sensor read-outs closer to zero where they should be. Instead the vehicle was raised and the negative Sensor readings persisted.
The second attachment shows “stills” from a video I made of the on-screen pressure changes during a “LO” to “N” rise of the vehicle. The videos were made as part of an effort to understand what the Levelling Valves in the Control Valve Assembly were doing and also, if possible, to confirm the operation of the solenoid valve on the Height Control Accumulator. (I am not sure what to make of the trace of the Height Control Accumulator pressure). The video file is too big to attach but the marked-up “stills” give the idea. They show the long response times and slow build-up of pressure. These solenoid valves in the Control Valve Assembly and the Height Control Accumulator have been checked by touch and sound and by the “Active Test” and do seem to be operating. Arthritic fingers have not yet succeeded in removing the electrical connectors and so resistances have not yet been checked per FSM, nor has continuity been checked through to the ECU. The new Height Control Sensors all operate correctly. Hopefully there are no blockages in the tiny filter “socks” inside the new AHC Pump! Underbody condition is excellent with no corrosion and no visible harness damage.
I have wondered whether there is mechanical interference somewhere, such as in the suspension bushings or between the airbags and their covers and the rear springs, when moving between “LO” and “N”. My Independent Mechanic thinks not. It all seems to work very well between “N” and “HI”.
Anyway, this is a long story with a lot of attached detail. All advice, comments, critique, ideas from anyone anywhere about what to do next would be most welcome. May I specifically tag @uHu, @PADDO, @LndXrsr, @Moridinbg, @2001LC, @suprarx7nut, whose insights on such matters always has been helpful.