My 2002 LX470 goes from Low to Normal to High with no problem. If I am in Normal mode and click to go to the High Mode, the LX moves up while the High light flashes. However, after the vehicle stabilizes in the High mode, the light goes back to Normal. What is going on?
AHC works, High light Doesn't
- Thread starter Gebo
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
go to your dealer and have them pull the codes. The truck isnt staying in high mode, it's reverting back to normal. could be lack of ahc fluid, ahc pump failing, a number of things.
wildsmith
SILVER Star
My guess (and that's all it is) is you have a sensor problem. If the sensors were all ok then as loud says it should be dropping back to N physicaly as well as on the lights. You should be able to get a code from the ECU to find out what's up.
It's not staying in high mode, if you want to believe that it is though fine by me. I've been having the same issue. Instead of trouble shooting it I've decided to take it out(two months now, freakin time is flying!)
- Thread starter
- #6
1LoudLX, I may not be the brightest bulb but I stand out side my LX and watch it raise from the "N" position and stay there. If you want to not believe that observation, then that is fine by me.
I raised it last night to "H". The light flashed on "H" as it raised. It raised about 3 inches, stabilized and the light went back to "N". I left everything like that, turned off motor, came in to watch O'Reilly. I just went out and started her up and the light is on a solid, non-blinking "H". How 'bout dem apples? Does this information help with any diagnosis?
I raised it last night to "H". The light flashed on "H" as it raised. It raised about 3 inches, stabilized and the light went back to "N". I left everything like that, turned off motor, came in to watch O'Reilly. I just went out and started her up and the light is on a solid, non-blinking "H". How 'bout dem apples? Does this information help with any diagnosis?
Do you have alot of weight in the back?
Sometime when you have alot of weight in them it doesn't go up to high immediately.......at least that whats happened in my experience.
Sometime when you have alot of weight in them it doesn't go up to high immediately.......at least that whats happened in my experience.
there is something wrong most likely, swing by a dealership and have them pull the codes from the AHC ecu. you've got three Lexus', if they dont do that for free start throwing things.
not sure. When I had the codes pulled the other week the tech used a toughbook with the TIS system integrated into it. Not sure if the codes, if there are any, could be read by a simple machine.
hoser
SILVER Star
You can check it w/o the handheld tester. You're going to jump two wires on a connector and count blinking lights. But you'll need an FSM.
wildsmith
SILVER Star
I don't think the suspension ECU will show up on an ordinary ODB-II unit. Best bet is a copy of the FSM which will tell you how to pull the codes yourself and what those codes mean and then how to test the parts they might identify as faulty. I think there's a link on here somewhere to an on-line pay version of the FSM's?
If you can do at least basic maintenance then with the FSM to hand you'll probably do a better job of figuring it out than the dealer
If you can do at least basic maintenance then with the FSM to hand you'll probably do a better job of figuring it out than the dealer
I have had a few occurrences like that in the past, before I cranked up the torsion bars and replaced the accumulator spheres.
The truck would raise to high, but before it "locked in" to position it would drop just a little bit, at which point the light would go back to normal. The truck would almost be at the correct height, but not quite. I also tried the test of turning it off, waiting a while, and then turning it back on. The truck would autolevel itself and the high light would come on. Also, if I just drove off with the truck showing the normal light, but near the high position, it would stabilise in the high position if I went over a few bumps, or drop to the normal position when I got up to speed.
I never diagnosed the cause, but I suspect that the pump is a little weak and struggled to lift the weight of the front with all my extra gear on there. The rear is well supported by OME 862 springs, so I think it was the front causing the problem. Since I have cranked up the torsion bars, the AHC pump doesn't have to work as hard to lift the front, so I haven't seen the problem again. It was rare anyway, and I suspect in my case it was in part due to hot weather, since it seemed to occur only during hot weather, and usually when the AHC had been "exercised" a bit.
I found my torsion bars were set near the bottom end of their adjustment, and cranked them up to near the top end when I fixed my suspension. As Tom suggests, try to tighten up the TBs and see if the problem goes away. I found that one turn of the TB adjusting bolt was equal to reducing the pressure in the AHC by about 45 psi. Therefore, I would suggest that you tighten the TB adjusting bolts by two full turns each initially, and see how you go. I also suggest that you clean the threads, soak them in some WD40 or similar overnight, and get the correct sized socket to do the adjustment. I had to replace one of my TB adjusting bolts and associated parts at a cost of about AU$150 because the thread was badly damaged. I suspect it was like that before I started, but it could have been some dirt getting in when I started adjusting it. With the front wheels completely off the ground and the front suspension extended, you should be able to easily turn the TB adjusting bolt with a one foot bar. If you have to put a breaker bar on it, don't. Something is wrong.
The truck would raise to high, but before it "locked in" to position it would drop just a little bit, at which point the light would go back to normal. The truck would almost be at the correct height, but not quite. I also tried the test of turning it off, waiting a while, and then turning it back on. The truck would autolevel itself and the high light would come on. Also, if I just drove off with the truck showing the normal light, but near the high position, it would stabilise in the high position if I went over a few bumps, or drop to the normal position when I got up to speed.
I never diagnosed the cause, but I suspect that the pump is a little weak and struggled to lift the weight of the front with all my extra gear on there. The rear is well supported by OME 862 springs, so I think it was the front causing the problem. Since I have cranked up the torsion bars, the AHC pump doesn't have to work as hard to lift the front, so I haven't seen the problem again. It was rare anyway, and I suspect in my case it was in part due to hot weather, since it seemed to occur only during hot weather, and usually when the AHC had been "exercised" a bit.
I found my torsion bars were set near the bottom end of their adjustment, and cranked them up to near the top end when I fixed my suspension. As Tom suggests, try to tighten up the TBs and see if the problem goes away. I found that one turn of the TB adjusting bolt was equal to reducing the pressure in the AHC by about 45 psi. Therefore, I would suggest that you tighten the TB adjusting bolts by two full turns each initially, and see how you go. I also suggest that you clean the threads, soak them in some WD40 or similar overnight, and get the correct sized socket to do the adjustment. I had to replace one of my TB adjusting bolts and associated parts at a cost of about AU$150 because the thread was badly damaged. I suspect it was like that before I started, but it could have been some dirt getting in when I started adjusting it. With the front wheels completely off the ground and the front suspension extended, you should be able to easily turn the TB adjusting bolt with a one foot bar. If you have to put a breaker bar on it, don't. Something is wrong.
Glad to see I'm not the only one having AHC issues.
Yeah, but I seem to have fixed mine, and get to enjoy the advantages of AHC into the future. You are gunna miss it once you get around to removing it from your truck. :whoops: 
wildsmith
SILVER Star
loud probably won't miss wondering if / when it's going to fail though Tough choice, I like how the AHC rides and I like having trick features but I don't like wondering if part way through my next wheeling trip it's going to fail and ruin the trip 
Tough choice, I like how the AHC rides and I like having trick features but I don't like wondering if part way through my next wheeling trip it's going to fail and ruin the trip
Well, I'm not that gentle on the truck. See my avatar. That's my truck a metre off the ground, jumping a sand dune. (Okay, back in the days before I added a s*** load of weight to it.)
Mine never actually failed, it just lost pressure in the accumulator spheres, and the TBs sagged a bit. Plus they were never tightened up when I added all the weight back in 2003.
However I have heard of people driving over a thousand kilometres to get back to civilisation in Australia with the rear end of their Lexus sitting on the stops, because they overloaded the rear and then kept pressing the button to raise the rear when it sagged, destroying the pump. So I guess I can understand the concern. As I said above, I think my AHC pump is a little weak these days, and may need replacement at some stage, but I can live with that.
Mine never actually failed, it just lost pressure in the accumulator spheres, and the TBs sagged a bit. Plus they were never tightened up when I added all the weight back in 2003.
However I have heard of people driving over a thousand kilometres to get back to civilisation in Australia with the rear end of their Lexus sitting on the stops, because they overloaded the rear and then kept pressing the button to raise the rear when it sagged, destroying the pump. So I guess I can understand the concern. As I said above, I think my AHC pump is a little weak these days, and may need replacement at some stage, but I can live with that.
Gebo, how long have you had this problem? Did it just start this winter or after driving in water/snow/high humidity? If so, then start with something simple like checking the AHC sensors. I'm sure someone here has taken them apart and cleaned them.
