AHC - Blinking Off

[CruiserGeek]

2002 Lexus LX470 - US model Gas V8 4x4 109K miles

The problem: Blinking "Off" light and stuck in LOW mode. Currently riding like a "low rider" and feels like I'm on a pogo stick. Cannot manually change modes with the switch on the console.

I have read several threads on this site and several other sites. I even applied the suggestions and have already spent $2500 US dollars and still have not fixed the problem. Yes, If i could go back and start over I would have just replace the basted factory AHC with an aftermarket lift/system, but I'm too far in now.

So far I have replaced the pump 48901-60010 ($300) , the Height Control Accumulator Assembly - 49130-60010 ($600), and all 4 Accumulator aka nitrogen globes or actuators - aftermarket's from B&B suspension ($1600).

I applied 12v DC directly to the AHC motor which drives the pump - it pumps great! When I turn the key on or even start the vehicle there is no voltage to the connector feeding the pump motor. I removed the control valve assembly and re-installed. I removed and inspected the two front and one rear height control sensors, they were all very clean and in great condition inside and out. I suspect they were replaced at one point. I have not replaced any of these parts - YET!!

I am not sure what to replace next...it seams as though something electrical, relay or sensor? Maybe something is telling the system not to apply power to the motor?

Any Help is appreciated!!!

Frustrated,

Mark

 

[BobMurphy]

Obvious I know - but have you checked all the fuses??

If the pump works when voltage is applied directly then there is either an ECU somewhere telling it not to answer the phone or its lost power.

If the fuses are OK I would try plugging in an OBDII Code Reader and see if there's a fault recorded. It may not be directly related to the AHC System.

Failing all that, I think you (or an Auto-Electrician) will have to check all the wiring for bad connections or breaks, checking any relays you encounter along the way.

Its a pain, but starting at the "cheap end" of a problem is usually the best way as Toyota stuff is quite reliable (unless its corroded by road salt - like ours here in Scotland).

Keep us posted, the shared experience is useful for those of us with AHC.

Bob.

 

[CruiserGeek]

Thanks for the reply Bob!

I checked the fuses, both the 50A under the hood and the 20A under the drivers side dash. Tested both of them to make sure there was not a hairline crack.

My ODBII reader does not show any codes at all...strangely enough.

I will start tracing down the wiring...

If you or anyone else has any other ideas, please shoot them over.

Mark

 

[t1pper]

Hi,
I am fairly new to landcruisers but I have noted that the AHC will not operate with the doors open maybe check for a door switch??
Its a long shot but worth a check and will not cost anything.

 

[Jmacd]

Hi Mark,

Their are a couple of things I would suggest you can still try.
Easy thing first. On the hydraulic unit where you fitted the new pump their are two sensors looking from the front.
first one has two wires (temp sensor). Second one has three wires (pressure sensor). With ignition off unplug the pressure sensor plug. I suspect your car being a year 2002 it will be a triangle type plug. With all doors closed start engine. If car rises to normal level. Your problem is pressure sensor.

to check the rest you really need a mulit meter. Nothing fancy just something to read ohms an volts.
check the ohms reading on the temperature sensor.

next you need the readings from the hight sensors. If you have any thing outside 0.5v to 4.5v on any of the three sensor
your AhC will freeze and you will need to adjust the position of the arm ( assuming from above that your sensors are ok).
best method I found to check the sensors is if you have some old toyota wiring harness parts. Remove three male and three female ends from there plugs. Join the male and female ends up and insulate the joints. You should have three individual wires with toyota male and female ends. Failing this see ŵhat wire and very small terminals your auto store has.
make sure nothing touches when fitted. I prefer this method as working under the dash trying to get to the right wire in the ECU plug is not easy.

On the front inner wings open one plug from the hight sensor wire to the wiring harness. Use your new harness to join the two ends up. With the ignition on read the voltage between terminals 2 & 3. Or 2 and ground. Record the reading. Remove the harness and reconnect the plug. Do the same for the other side. You need to move to the rear next. Put stands under the chassis before working under the truck. Take the same reading from the sensor as before ( think your truck has only one sensor on rear but check. I think 2004 on had two). If you have a reading outside 0.8v and 2.53v. You need to readjust. Provided sensor is good.
On the hight sensors red, black wire is +5v. Green yellow is ground other wire is terminal 2.

after this if no results do the same on the pressure sensor. Measure the value of t2.


let us know how you get on. The toyota can give you the fault code but I Find it's often miss leading especially if the codes have not being cleared leading you on a false track.

good luck.

 

[Jmacd]

Forgot Temp sensor should be 2 to 2.9 Kohm at 20 C.

Make sure to keep the wires correct when joing up. I to 1, 2 to 2 and 3 to 3.

 

[uHu]

If you connect to TechStream, it's easy to see if one of the height sensor signals are off, or any other sensor.

 

[frank rabbets]

The height control switch firmly plugged in?

 

[ankitpatel]

Hi Mark,

I would highly appreciated if you could share your experience after the above problem. i have 1999 LX470 and causing the same problem as yours. could u please briefly let me know what was the immediate action did you take after the above issue. your review will be helpful to me. Thanks in advance.

Ankit

 

[PYLC]

HI,
I'VE YTHE SAME PROBLEM WITH MY LC 4.2 VX, HDJ101 MODEL.

I'VE REPLACE THE 4 ACCUMULATORS, HEIGHT CONTROL PUMP (BELOW THE HYDRAULIC TANK), CHECK ALL 3 SENSORS. BUT TILL TO DATE, AFTER MORE THEN 3 WEEKS, I'M UNABLE TO LOCATE THE FAULTS.

WILL APPRECIATE IF ANYONE CAN SHOOT ME THE ANSWER. THANK YOU

 

[frank rabbets]

If the system has been drained of fluid the pump sometimes does not prime itself so the system is dead. I had that problem with mine after changing the fluid. I undid the outlet pipe on the pump and allowed some fluid to drain out under gravity. Perfect afterwards. I would have tried running the pump with that pipe off if that had not worked. It's very messy whatever.

 

[uHu]

HI,
I'VE YTHE SAME PROBLEM WITH MY LC 4.2 VX, HDJ101 MODEL.
I'VE REPLACE THE 4 ACCUMULATORS, HEIGHT CONTROL PUMP (BELOW THE HYDRAULIC TANK), CHECK ALL 3 SENSORS. BUT TILL TO DATE, AFTER MORE THEN 3 WEEKS, I'M UNABLE TO LOCATE THE FAULTS.
WILL APPRECIATE IF ANYONE CAN SHOOT ME THE ANSWER. THANK YOU

1: A bit more info, please. What are the symptoms, what works, what's the levels and values of the AHC system, what mods, changes and repairs have been done, what's the build year/month, and what's the milage.
2: What are the readings for the sensor values in TechStream or any other code reader.
3: Please don't shout (capitals...)

 

[PYLC]

I've changed the pump, as well as all 4 accumulator, 6 months back. After that, the problem.will be riding the vehicle like a pogo stick. The LC is a 2003, 4.2 VX . Last month, due to frustration, I change the pump below the tank. Change the control swicth, next to the gear. Have check all 3 height sensors and found them to be in good condition.. Release more a liter of oil, too, but still the problem continue. I've used up too much cash and at a lost at what to do next. I'm going to send the LC to a friend workshop to check all the electrical parts and values. I'll also flush off 1.5 liters of the oil from the bottom pump and too up with next oil. Recheck the sensors, as well as the height of the sensor, of which, I've not done. Appreciate if anyone FACING the same problem to share their experience to rectify these sticky problem which I notice, many LC owners face.

 

[PYLC]

Oh, the mileage is 302,000 km. Just return from a gearbox overhaul, 2 weeks ago. 6 months ago, I connect the motor directly to raise the height, similar to Medium. The blinking stop, but the ride hardness, as well as the height cannot be adjusted. The system was dead 6 months ago, THOUGH blinking lights are gone. I suspect.that when the vehicle was raise to a certain height, the sensor send the stop signal to the motor informing the LC have reach its desired height.

 

[PYLC]

AHC Blinking Lights - SOLVED!

Hi everyone who have the same AHC Blinking lights problem. Like everyone here, we all get all the wrong information or all the information received did not hit the solve button correctly. Though, I've to admit that I change many parts like everyone here who have the same problem.

I've change the accumulators (4 new pieces) accumulator pump, motor for the oil tank as well as the AHC switch which look a little corroded due to drinks spilling over it. After changing and checking all these parts, it still refuse to activate the motor below the plastic oil tank. I almost gave up and wanted to settle to adjust the height through direct connecting to the motor to lift the LC up.

After much frustrations, I dismantled the whole tank and motor assemble. On removing the tank, I inspected it, and there are some very fine black dirt at the bottom, which I've clean it.

I then remove the new motor below the tank and again found that the new motor is running well and strong. On the other side of the motor, there's a CUP LIKE shape with 3 screws. I remove the cup or cover. I found in the part that's cover by the motor have very fine black powder like dirt (Less then the amount of 1/8 of a teaspoon with very fine bubbles. Again, the bubbles are less the ten bubbles) I clean and blow out anymore dirt or water that's still remaining inside. Reinstall it, and start filling NEW oil into the tank.

Started the vehicle, you can see the LC body raising up very slowly. It's getting back to normal. Off the engine, and restart after 7-8 minutes, as I wanted to check with the engine off, will the LC sink down again, but it did not and maintain at the same Height.

I then raise the LC to H level, it moves up slowly, tried few times from L, N to H, all in perfect condition. Next I ran the LC over road bumps, I can feel the rear wheel hit to top. Send back to my home and adjust the LC sensor lower. and run the LC over different road condition. It work perfectly.

 

[lc 120]

Excellent. pleased to hear you have solved your problem.....

 

[Gerrit]

Hi there! How is everyone doing tonight? I have an 2006 land cruiser station wagon. It is an import to South Africa. The problem is the AHC is not working. The off indicator light is flashing continuously and the green light stays at N even when I push the H or L button. I have tested all fuses and the two main relays and all is fine. Has anyone had a problem like this?

 

[PYLC]

Hi, Good morning to everyone. I'm sorry to know that you've the same problem as mine. As mentioned in my reply to the group, I did managed to rectify the problem after changing many parts. But it still do not work.

Finally, out of frustration, I dismantle the whole reservoir (Where you add in the hydraulic fluid) This is the part that the small pump are installed. On the reverse side of the pump location, there's another piece which is similar size to the pump. I dismantled it found that there're a drop of black fine dust with about 2-3 drops of water.

After flushing and blowing it cleaned, Install, and everything works perfectly. Hope you've the same problem and advice you to trouble shoot this part where dust and water may have accumulated, instead of changing parts after parts. Hope this will help you out. Good luck.

 

[Gerrit]

Hi, Good morning to everyone. I'm sorry to know that you've the same problem as mine. As mentioned in my reply to the group, I did managed to rectify the problem after changing many parts. But it still do not work.

Finally, out of frustration, I dismantle the whole reservoir (Where you add in the hydraulic fluid) This is the part that the small pump are installed. On the reverse side of the pump location, there's another piece which is similar size to the pump. I dismantled it found that there're a drop of black fine dust with about 2-3 drops of water.

After flushing and blowing it cleaned, Install, and everything works perfectly. Hope you've the same problem and advice you to trouble shoot this part where dust and water may have accumulated, instead of changing parts after parts. Hope this will help you out. Good luck.

Hi, Good morning to everyone. I'm sorry to know that you've the same problem as mine. As mentioned in my reply to the group, I did managed to rectify the problem after changing many parts. But it still do not work.

Finally, out of frustration, I dismantle the whole reservoir (Where you add in the hydraulic fluid) This is the part that the small pump are installed. On the reverse side of the pump location, there's another piece which is similar size to the pump. I dismantled it found that there're a drop of black fine dust with about 2-3 drops of water.

After flushing and blowing it cleaned, Install, and everything works perfectly. Hope you've the same problem and advice you to trouble shoot this part where dust and water may have accumulated, instead of changing parts after parts. Hope this will help you out. Good luck.

Good morning! I will strip the reservoir and pump and see what i can find. Thanks for the advice!