ALAN553

going back to Lexus today. Rear has been dropping down while driving and not coming back until I either turn it off and restart engine or I manually raise it. No blinking lights on Height control, I can raise and lower suspension normally but for some reason every so often suspension drops w hile driving and does not come back up. I can tell immediatly when I am riding on the axle. It seems the height sensors are working, maybe just not communicating with computer? I read somewhere here that after you clear codes from ECU you should not clear DTC C1735. I wonder if mechanic knew that or if that is even the problem. Let you know..

RCsGX

Damn that sucks to pay that hefty bills and still have a problem. I hope they don't fine a "new" failure so you don't have to come out of pocket this time. We should start nick-naming our GX the BOAT....

Break
Out
Another
Thousand

ALAN553

Just dropped it off. Reminded them that I thought 4 hours labor at 125/hour was a bit high in the first place....they are a pretty honorable dealership, They offered me a free loaner which I did not need, I told them thanks, just fix the truck!!! Let you all know tomorrow what the verdict is. Maybe just a ECU programming thing.

ALAN553

Just picked it up, all they did was recheck for error codes...none. So I found this post..

.Only one important thing the dealer should remember that there is Code DTC C1735 is not removed and it should be retained in the Suspension Control ECU.

And I showed it to them...they obviously remove all codes. I asked if this one should remain? Height control works properly from switch, no blinking light. If suspension is at normal height when I turn it off, it is still there in the morning. But I am losing height while driving and the system does not bing it back up unless I do it manually, or a shut off engine and restart, compressor raises is. What is this DTC C1735 code? How does it figure into the problem. Are sensors not communicating with ECU? Can it still be sensors without fault codes? They told me to bring it back next week. They are short handed due to snow storm..,

RCsGX

Not sure what the problem is but I'm attaching a zip file w/ PDFs for you to read through that deals with code C1735, which the code is:

DTC C1735/35 : EXHAUST SOLENOID VALVE CIRCUIT

470reasons

Will the height reset if you turn the ignition key to the 'start' position with the engine running? Maybe you could use this trick 'till you get the problem fixed???

ALAN553

C1744 AND C1761 were on the original work order that led them to the ht control tank/solenoid.

RCsGX

C1744/44 : TANK SOLENOID VALVE CIRCUIT
C1761/61 : (SUSPENSION) ECU MALFUNCTION

See attached zip files....

ALAN553

Well that would lead them to the reservoir and solenoid...but it it is still winding up on the bump protectors while driving...Sometimes.....is it possible it is still the height sensors even though they show no codes or blinking dash light? I was stopped at a light and out of curiosity tried to put it in L...the light never even blinked, it just lit up the L..because it was already down. Pushed up and it went......

RCsGX

The codes for bad ride height sensors are:

Left: C1714
Right: C1713


It doesn't appear that you have a bad sensor(s) since you said you pressed "HI" and the rear lifted up.

• When the suspension control ECU detects a malfunction in the height control sensor, the height control indicator lamp ”N” comes on or blinks, and the height control switch (”HI” and ”LO”) is suspended.
• When either one of the right or left height control sensor sub−assy is faulty, the suspension control ECU uses the other one (functioning one) to adjust the vehicle height to the normal height.
• When both of the height control sensor sub−assy are faulty, the suspension control ECU suspend the height control function immediately.

EDIT:
Based on what I can find here are the main problem areas that would cause what you're experiencing:

1. Air leakage
2. Clogging of the air tube
3. Height control sensor link sub−assy (Ride height sensor linkage)
4. Height control sensor circuit (Ride height sensor)
5. Gate solenoid valve circuit
6. Suspension control ECU

ALAN553

True system works normally from dash switch.. And if I park the car overnight and the suspension is at correct height, it is still there in the morning...so a leak? It is dropping while I am driving and sometimes correcting itself. I hear the pump while waiting at a light. .I will take your list with me when I bring the car back next week..thanks.

RCsGX

Hopefully they get it figured out.

ALAN553

Zero up here this AM, it's wonder anything mechanical works

MTLT

This needs a little clarification. The bottom of the spring does not need to be secured to the axle, Toyota has had the floating spring design since the FJ80 series Land Cruiser in 1991. The current air bag system in the GX470/460 also floats on the axle and frame, there is nothing keeping it from coming out except for a tiny clip on the frame. Toyota has designed the suspension where the shock is the limiting factor, the spring/air bag simply cannot come out unless the shock out travels the springs/air bag. As long as you have the proper shock matched with the coil spring everything will stay in place.

RCsGX

9 out of 10 people are going to be lifting their GX IE: not using stock shocks, so the hold down is absolutely necessary.