@suprasvobodea -- you certainly have had more than a fair share of frustrations!! Hopefully a fix soon emerges.
The above Posts from
@suprarx7nut and
@Moridinbg contain excellent leads based on their deep knowledge and experience -- it is always worth following these guys ….
To add a bit more, a ‘long check list’ has been created in this very long Post. It may be TLDR – apologies offered, past mid0night on the East Coast of Australia, too late to try to reduce the length.
The limitation of trying to provide assistance on a Forum such as this is that the vehicle cannot be seen nor heard nor felt by ‘advisors’ on IH8MUD and coordinating phone calls across international time zones is too difficult -- and so misunderstandings and wrong conclusions are all too easy!
The ideas below are meant to provide @suprasvobodea with information along with some comments -- a range of items to be considered -- a ‘check-list’. @suprasvobodea will know what has been done and what merits further attention in the list below and what is not worth further effort.
Actual Part Numbers checked at the Partsouq website have been used to identify component parts and avoid confusion where different people may use slightly different words (for example, between different seals and O-rings). Partsouq or other sites or Google search can be used to quickly find pictures of relevant components ….
Let’s start at the beginning ….
If previous Posts have been understood correctly, the following AHC components have been replaced with new OEM parts by
@suprasvobodea:
-- all four ‘globes’,
-- all four ‘shock absorbers’,
-- Height Control Accumulator,
-- Pressure Sensor (twice),
-- AHC Pump sub-assembly inclusive of seals and O-rings (not gearcase O-rings),
-- AHC Fluid.
There are suspicions about the solenoid valve at the Height Control Accumulator. However, the Height Control Accumulator is
NOT vital for bleeding nor for raising the vehicle. The AHC Pump can and will do this, just more slowly,
provided that the AHC Pump sub-assembly is able to work correctly.
@suprasvobodea advises that all Height Control Sensors have been opened, inspected and tested electrically per FSM.
The Damping Force Control Actuators, the Control Valve Assembly and the ECU have not been reviewed.
It is unclear how much harness and circuit review has been done and whether or not damaged wiring is a contributor to DTC C1762 on this vehicle.
It is assumed that all AHC-related tests were conducted with wheels on the ground, all doors and rear hatch closed (and no faults in door-light circuit), foot-off-brake (and no faults in brake-light circuit), steering straight ahead, etc, etc (all of which cause AHC conflicts), plus engine started (not just ignition switched “on”).
The vehicle is stuck at LO height (or maybe on the bump stops?), will not raise, and persistently presents Diagnostic Trouble Code (DTC) C1762 with the FSM-specified response time of 0.6 seconds. This DTC C1762 returns almost immediately (0.6 seconds) after it has been cleared by Techstream or manually when the vehicle is re-started.
This means that the AHC/TEMS system is following its settings to protect itself from further damage (and maybe Toyota/Lexus would say protecting the Driver and Passengers from misadventure).
In the case of DTC C1762, as specified in the FSM, the ECU puts the vehicle into “fail safe function” and causes the vehicle to default to the lowest AHC height at any wheel (in this case LO height is reported) and also to default to Step 8 (mid-range of the 16 steps of the damping settings available in TEMS).
No other DTC’s have been reported. (They may exist -- but the quick-acting DTC C1762 may be responding first, masking other fault conditions yet to be revealed).
In this DTC C1762 “fail safe function” condition, the vehicle cannot be raised, nor can there be any continuous auto self-levelling in real time -- which is the basic Active Height Control (AHC) purpose. Nor can there be any continuous real time adjustment across the 16 damping steps, responding to road conditions in real time -- which is the basic purpose of the Toyota Electronic Modulated Suspension (TEMS).
The vehicle will remain in this condition until the cause of DTC C1762 is found and resolved.
The “Active Test” whose full name is the “Height Control Operation Test” cannot be used while DTC C1762 prevails. It is not designed to be used to by-pass the hydraulic protection provided by DTC C1762 or other protective DTC’s. That is not its purpose. To do so would be the hydraulic circuit equivalent of by-passing a burnt-out fuse in an electrical circuit with a nail. We could wish that the designers made different arrangements when the TEMS system was devised and used on the Toyota Soarer in 1983 and later adapted for use in Lexus LX470 in 1998 and onwards and also as an option on some LC100 models. The Toyota/Lexus designers have not changed the design for 100 series – there are differences in the evolution on 200 series and 300 series.
The cause of DTC C1762 on this vehicle remains elusive.
Air in the AHC system seems an extremely likely cause of DTC C1762 on this vehicle given the hydraulic circuit disruptions required for the component change-outs.
Along the way a fault with the AHC Pump has emerged. This is preventing the cause of DTC C1762 from being confirmed and preventing the vehicle from being raised and lowered as part of a normal bleeding process.
Even when connected directly to a 12 volt DC source, weak low pressure Discharge is observed from the overall AHC Pump assembly (the whole thing -- Part Number 48910-60012)
on open circuit with Discharge pipe detached. This is described by
@suprasvobodea as a dribble from the open Discharge which can be stopped with a finger, even while the AHC Motor and AHC Pump continue to run.
Clearly, AHC Pump does not develop pressure against resistance as it should (and indeed as any positive displacement external gear pump should).
It is the result of a fault in the AHC Pump assembly
There are only the following possibilities for this situation, some are more likely than others. For completeness, here they all are, starting from the motor and working towards the Pump sub-assembly:
- The AHC Electric Motor 88264-60010 is faulty -- this seems extremely unlikely, given that the motor works when connected to 12 volt DC supply, The pump is working . ITs a bit stiff, but it runs - in both directions.
- The electric motor 88264-60010 is not engaging the Pump sub-assembly 48901-60010 properly – this seems highly unlikely -- but it is worth checking the small connector “shaft” 48977-60010 which passes through the milled aluminium housing 48905-60010 and through a seal 90311-10001. This tiny “shaft” connects the motor on one side of the housing and the driven gear in the Pump sub-assembly 48901-60010 on the other side – and it is worth being satisfied that all parts are engaging properly, I watched the opposite side of the pump , where the other side of the gear shaft it and i see that the ends of the shafts are spinning. - The tiny shaft is functioning!
- AHC Fluid is not reaching the Pump sub-assembly 48901-60010 -- this does not seem very likely -- nevertheless it is important to be satisfied that there is no blockage or restriction -- such as might be caused by gel or other gunk -- (a) at the base of the AHC Tank and where it joins on the housing 48905-60010, and (b) that there is no blockage of restriction in the fluid path through the housing 48905-60010 to the point at which the AHC Pump sub-assembly 48901-60010 picks up AHC Fluid. The simplest way to check this might be to remove the Pump sub-assembly and check that there is a good gravity feed of AHC Fluid from the AHC Tank. (I have wondered whether this can be checked by pushing a pipe-cleaner or piece of wire or similar through this passage -- but this might run into the Return Valve within the housing and cause confusion and/or disrupt the Return Valve), I blew air into the container from the opening and it escaped freely thru the botttom -- There is NO blockage - per your this does not seem very likely
- Air is being drawn into the AHC Pump sub-assembly 48901-60010 -- this is possible and certainly would cause DTC C1762– it is important to be satisfied that the following seals are working as intended, not wrongly fitted, loose, worn or damaged in some way which would allow air ingestion due to negative pressure (sucking) on Intake side of the AHC Pump sub-assembly 48901-60010 when it is operating:
- seal 90385-08017 between AHC Tank and Housing 48905-60010, REPLACED with NEW
- Seal 90311-10001 at small connector “shaft” between motor and AHC Pump sub-assembly 48901-60010, REPLACED with NEW
- Large O-ring 90301-70003 between detachable outer cover 48913-60010 and Housing 48905-60010, REPLACED with NEW
- Any external gear pump (of which the AHC Pump sub-assembly is a micro example compared to industrial scale gear pumps) has a low pressure side (at the Intake) and a high pressure side (at the Discharge).
- In any external gear pump (including the AHC gear pump), the high pressure side and the low pressure side are separated by seals -- the design and location of seals can vary but the principle is always the same,
- In the AHC Pump sub-assembly, the relevant seals are:
- the triangular-looking O-ring under the top-plate,
- the O-rings on the gearcases,
- the small O-ring 90301-06012 where the Discharge from AHC Pump sub-assembly joins the Housing 48905-60010 near the Return Valve, REPLACED with NEW
- If ANY of these three seals weaken or fail, or if during dis-assembly and re-assembly of the AHC Pump sub-assembly the top-plate is insufficiently tightened, then AHC Fluid WILL leak from the AHC Pump sub-assembly into the region behind the outer cover and from there, back to the AHC Tank, WHAT ARE THE TORQUE SPECS FOR THE 2 ALLEN SCREWS THAT CLAMP THE PART HALVES, AND THE LONGER ONES THAT CONNECT THE PUMP TO THE FRAME? I dont have a torque wrench for allen screws , but i can figure out something
- @BullElk highlighted this situation when he found that the O-rings on the gearcases required replacement and that rectified the no-flow condition in his AHC Pump -- @BullElk had stopped the leak and restored correct AHC Pump operation, WHat post # in this string is his description ? Or is this a totally different post ?
I don't have any tiny rubber bungs like I used in the outlet thread area, but I guess I'll try that tomorrow morning!
