Probably you have already done this, but for completeness suggest check and test battery and charging system – the method probably is well-known to you but also see description at
LC100 Workshop Manual - https://lc100e.github.io/
then the following further tabs:
Engine Repair Manual [2UZ-FE] > CHARGING > CHARGING SYSTEM (Page CH1 or Page CH2 depending on Model Year)
Anyway, assuming that the charging system is in good order and returning to your screenshots ….
I don’t understand what causes the Techstream message “Lost Communication with the vehicle” but maybe that is not particularly relevant.
The first screenshot -- shows one unidentified DTC – temperature is -22degF, so this DTC would be due to temperature sensor being disconnected, otherwise all values look normal in all respects, including
IG 13. 7 volts and +B 14.1 volts. Interesting -- don’t recall seeing +B greater than IG on other AHC screenshots on IH8MUD – but maybe I have not been observant enough and/or maybe that just represents a fully charged battery in good condition? Or does it suggest a alternator/regulator on the way out?
The second screenshot – shows no DTC’s, temperature 100degF seems reasonable, all other values look reasonable in all respects, including
IG 13. 7 volts and +B 12.9 volts – with +B is 0.8 volts lower than IG and also +B is 1.2 volts less than +B in the first screenshot.
These IG and +B voltages
on the second screenshot do not seem unusual to me and are consistent with most other screenshots I have seen on IH8MUD over recent years. My own most recent results (DEC ’21) with vehicle operating normally with new batteries (two in parallel in 1HD-FTE) and new OEM replacement Toyota/Denso 27060-17230 alternator (long story!) were:
IG 14.0 volts and +B 13.2 volts
IG 13.8 volts and +B 12.9 volts
The third screenshot is a puzzle. It shows one unidentified DTC, not temperature sensor this time, temperature is high at 129degF suggesting pump has been working hard (?), height sensors are all high but closely grouped within 0.3 inches of each other, Front and Rear AHC pressures are somewhat high – maybe corresponding to height of vehicle (?), Main Relay Expectation is “OFF” (?) but “ON” on previous screenshots,
IG 12.1 volts (low), +B 1.7 volts (extremely low).
Ordinarily, this would raise suspicions about an under-charged battery as would expect to see around 13 volts on the distribution system from the battery. Assuming the charging system is healthy, that would suggest checking the 15Amp AHC-B fuse and the 20Amp AHC-IG fuse (both in the junction box behind the kickboard on the LHS of the LHD driver’s footwell) and also checking the operation of the AHC Main Relay (which is mounted on the AHC ECU under the dashboard
.
In theory, nothing is going to happen, including “Active Test”, in the AHC/TEMS systems if these items are preventing delivery of electrical power.
However,
in practice the third screenshot also shows that the vehicle has been raised with reasonable although somewhat high Front and Rear AHC pressures and normal Height Control Accumulator pressure. This did not happen without the operation of the AHC system – or are these readings old readings which have not been cleared from the ECU??
The third screenshot shows a DTC – has it been possible to identify this DTC?
The ECU response to disable AHC (and initiate protective ‘fail-safe functions) could happen in 0.5 seconds or 2 seconds (if C1743 depending on circumstances), or in 0.6 seconds (if C1762).
So apologies @2001LC – I don’t get what has happened in the circumstances depicted in the the third screenshot. As a Iate edit I have wondered if the vehicle is still capable of being raised by the AHC system-- perhaps slowly compared to expectation -- then a possibility might be a partially blocked AHC Pump -- but that does not fit with the voltage readings which suggest that neither the AHC circuit nor the AHC Pump is receiving electrical power. There must be a better answer -- I think I am missing something.
Hopefully other IH8MUD Members can be more helpful!
As well as the charging reference given far above, I have had a look at the following references:
LC100 Workshop Manual - https://lc100e.github.io/ (This is an LC100 FSM but should be good enough for LX470 purposes).
then follow these tabs in the menu on LHS of opening page:
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL & SKYHOOK TEMS
then the following further tabs:
Power Source Circuit (Page DI-294) – with engine running, need
battery voltage (+B) of 10 volts to 16 volts, and,
ECU terminal voltage (IG) of 9 volts to 14 volts – to enable operation of AHC Pump & Motor and Damping Force Control Actuators (TEMS). If not, check/test the circuit as described, including
AHC-IG fuse (behind LHS cover in LHS footwell) and continuity of harness and connectors back to ECU. [Note: These voltages only define what the AHC ECU would accept -- see the first reference far above for the necessary voltage specifications for a healthy Charging System].
also
Tc Terminal Circuit (Page DI-306) – check/test correct voltage is present at terminals DLC3 socket under dash used for Techstream (otherwise Techstream will not operate correctly).
also
Ts Terminal Circuit (Page DI-308) – further check/test correct voltage is present terminals at DLC3 socket under dash used for Techstream (otherwise Techstream will not operate correctly).
then
C1741 – AHC Motor Relay Circuit (Page DI-243) -- check/test whether the relay is working – if not, no power to AHC Pump, ‘fail-safe function’ occurs as described, and there is no AHC/TEMS operation.
and especially
C1743 – AHC Main Relay Circuit (Page DI-248) -- check/test whether the relay (mounted on ECU) is working –
if not, no power is supplied to the ECU or any part of the AHC system, ‘fail-safe function’ occurs as described (note the three different conditions, 1 or 2 or 3 which are difficult to understand!) -- response times are 0.5 seconds or 2 seconds (depending on circumstances), then there is no AHC/TEMS operation including “Active Test”.
C1762 – Fluid Pressure Abnormality -- Pump & Motor Does Not Supply Fluid (Page 256) – check/test circuit, note that the response time is very quick ~0.6 seconds to protect pump -- and then there is no AHC/TEMS operation including “Active Test”.
Thanks for dropping in, and taking the time here. You are such a comprehensive and talented writer with a good grasp on AHC. I was hoping you would help out here, THANK YOU!. I've read the link you once gave me, "new model outline, AHC". Very good info, I'd never read/seen before. Thank you!
I also hope others like
@PADDO @suprarx7nut @uHu just to mention a few, stop by. As I'm seeing some tough cases, and I can use help on them.
The first two pictures in OP of tech stream, are old file pic's. One's form my
00LX470 w/670,000K (~360K miles), which I've a thread in mud on. It's AHC, works okay. One could say very good, considering age and miles. Those where just old pictures I had on hand, that I posted here for comparison. I never really looked at voltage before now. I found the +B voltage being higher than IG curious also. Perhaps it has to do with temperature senors being unplugged as does the -22F temperature.
The: "Lost Communication with the vehicle” seen in first two tech stream screen shots. Is just because I lose connection with tech stream, when I turn Key ( IG SW) to OFF to to off engine.
Thank you the very thoughtful and well written diagnostic tree. I've done many, but not all. I'm going back through all next few days.
Battery & charging system, seems to be working well. Battery holds about 12.5 to 12.7 on its'a own. I get 13 to 14 engine running. Battery was sulfate last December, but my charger corrected. Although I do have some concern with electric system (not charging system at this point), as some history of electrical gremlins with LH DS mirror and steering column motor. Seem 2 different Dealership years apart. Replaced a CPU (IIRC, I'll double check on what was R&R later) for DS mirror. It keeps failing, as does steering tilt.
I do have a C1736, C1736 DTC currently. The C1736 came up after unplugging all 3 wire housing blocks at pump (Motor power, also pressure and temp sensors)
I'll come back to current issue in next post. But first some history on this 2001 LX470:
__________________________________________________________________________
Sorry this is going to be long:
I'm first going to give history of this 2001, which is 3rd picture with the very low +B voltage. I'll use a subsequent post to talk about current issue with it.
The third picture is of a 2001LX w/145K miles. I'll give a little history on: NOTE:
THIS IS FIRST AHC ISSUE IN 2021. It has now come back with AHC issue I'll come back subsequently with current 2022 ISSUES. But first some history on 2021
It's a clean, rust free 100 series on it's 3 rd owner. No know accidents or signs of. First owner keep in a Garage IIRC in Vail CO, best we can tell. Indications, were it sat extended periods not driven, with first owner.
2nd owner brought to me, to repair of LH mirror and steering wheel tilt not functioning. I found both motors and SW's worked. Once I jump steering tilt motor with 12Volt by use of telescoping wire harness, it began reluctantly working. Was able to get mirror working through tech stream. The more I used them both, the more reliable they functioned. I chocked it up to lack of use. 100 series like all system used frequently. Most notably component we see issues with when not, is the CDL. Anyway I recommend, baseline including flush and adjust of AHC. But never I did any of that, and found it was never done by second owner.
3rd owner.
He brought to me when AHC failed, after buying and driving for sometime:
AHC OFF flashing, ride bounce, both front and rear high (rear was extra high).
It was taken to a Toyota Dealership before bring to me, without results. Only a statement "CUST MAX 1 hr diagnostic time","not enough time to diagnos". He was charged 1hr.
I found (Dec 2021):
AHC flashing OFF on dash lights.
* Sensor arms frozen. (Note "A" bottom of page)
Ride height high and bouncy.
DTC: C1736 Accumulator Solenoid Circuit.
DTC: C1762 Abnormal Oil Pressure for pump.
Going through diagnostic tree in FSM. In tech steam, activating relays & solenoids, I'd get: "ECU cannot perform the request Active test"
I did NOT do one test, in tree. In which we 're directed to test pressure sensor. But moved on to looking at ECU, as it seem I could not get any response from it. But I could hear sound from it or it's relay on the side of it. Which FSM direct us to listen for sound as IIRC.
It was my first time trying to take out a AHC ECU. I saw this was going to be very tough & time consuming to get in and out. I considered calling one supper nice mud guy
@RicardoJM, who's in my neighborhood. He let me pull AHC stuff off his LX, which he convert to non AHC years ago. I was thinking, I'd pull his computer and plug it into this rig as a test.
But first knowing Andy (
@suprarx7nut) had pulled one (AHC ECU). I called Andy. He said: he followed same tree. Although it direct us to test ECU, it was not the issue (or was not on one he worked). He found a dead wire under rear 1/4 near rear bumper on LH side. Nice work Andy... Kudos!
So I started looking around under rear 1/4 LH, Rear sensor back to rear LH corner of bump. Found the wire block housing and unplugged it, then plugged back in. I did get some results.
I went on to find the rear sensor damaged, not just frozen adjuster arm. First I unplug & re-plugged in, and system worked but height wrong. I disconnect arm and set height sensor by hand. I was able to get to height to change. Eventually I remove straighten bracket of sensor and cleaned it. AHC system than worked. But failed again after a few drives. So I installed a replacement rear sensor. System now work heights near normal.
Adjusted sensors & T-bars, after replacing front senor arms and rear season w/arm. To get heights and pressure near factory as I could. With a few drives around the block (1 miles with bumps and turns) between T-bar adjustments. I turned LH t-bar 6CW and RH 3CW Mpa now
Ending readings: Frt 19 1/4" RH & LH, rear 20 3/8". Frt 6.9, Rear 6.5, Accu 10.6 Mpa w/ 10 graduations.
AHC system now working as it should. Comfort to Sport had good response. Damping in turns very nice raised and lowed within spec times. Braking damping good. Nice ride. All in all, very nice.
But failed again on a longer drive. One in which I actively raised and lowered many times. Then while braking, AHC failed, light flashing OFF.
I drove until I could pull over (about 15 minutes). Turned key off and on again starting engine. AHC began work normally. My though was excessive and rapidly raising and lowering, heated fluid. Either heat trip or lower pressure further dropped by heat, caused this failure. I tried a few more time to get to fail, by raising and lower often at every stop. It did fail. Let it cool and began working again.
My though was pressure had gone to high, after driving and settling in. Which resulted in over working the system heating fluid. I see pressures a little change often, especial with old globes after settling in. So I hook-up tech stream and sure enough pressure are up. I don't recall to what, but cranked on T-bars CW, dropping pressure again. Dove for a week actively use L-N-H and confront to sport. No issues handled and rode very nice.
Owner pick up and report drive home through the mountains was outstanding.
3 months later it failed again.
* Notes: I'd not mentioned sensor arm frozen earlier. I had found all 3 sensor's arms frozen, in first look-over. This has become very common to see these ball of adjuster arm frozen in socket. So much so,
I've started a new PM: lubing the AHC adjuster arms. I do this with moly grease and a needle attachment on end of grease gun. I inject grease under (from inner side), not through the boot. The hopes is extending life of these arms. But eventually IMHO,all will need replacing.
Front sensor arm frozen and bent
