Quick question about AHC ride with extra weight (6 Viewers)

[ParaJake]

Hey guys, I have a 2006 land cruiser and I like the ride on it for the most part but I feel I may be missing out on something due to having AHC problems. Everyone says the land cruisers ride like clouds, but its not all THAT smooth to me. It rides pretty good, but only slightly better than my 2003 stock 4runner that I traded for this 100 series.
My 100 won't drop to low or lift up to high. This isn't a huge issue to me if its not causing any deficit in the ride. But, I had never ridden in a land cruiser prior to buying this one and I have never ridden in any other land cruiser so I don't have anything to compare it to.

After starting my car and driving for a few seconds, the AHC OFF light flashes constantly. I had this checked by a Toyota dealership and they said it was all of the height sensors. Does this sound right? That ALL of the sensors are bad? Or is it a fluke?

I'd love to get this thing working 100%, but I can deal with non-working AHC for now.

My main question is about riding with passengers in the 2nd row seats. When I have passengers in the second row, the ride gets very bad and I feel bad for the people in the back. It feels like the suspension is bottoming out with no more than 500 lbs in the back seat. This can't be right as I know the towing capacity is way more than that and I know that this thing is rated for more than just a measly 500lbs of human flesh bags in the back. Its actually more like 400lbs. Could this rough ride be due to a failing AHC system? It doesn't ride bad with myself and another in the front seats.

Also, does the ride stiffness control knob (next to the AHC position button) work if the AHC height sensors are bad?

I'd like to mention also that my AHC height control has never worked since I bought this about 7 months ago.

 

[ParaJake]

I didn't read this whole thread, but I once had a problem with my AHC not working and the lights just flashing when I tried to go up or down. The problem ended up being the wires going from the body to the lower tailgate had gotten pinched and one was broken so the ecu thought a door was open and wouldnt work.

I did have this thought and checked all the wiring for the doors. It all looks unscathed and all open doors do trigger the open door light.

 

[ParaJake]

@Rebus Knebus
I'm having a hard time finding the AHC Main relay under the dash. Looking under there in an extremely awkward angle, there are no relays that are jumping out at me. A LOT of wires and plugs, but no relays. Is the grey box on the far right of this pic the suspension control ECU?

 

[ParaJake]

I'm about to connect 12v from battery direct to pump because its the easiest thing to do right now. Does it matter which lead goes to which pin? Since it's DC if the leads are reversed, would this cause the pump to run backwards?

Edit: I took a look at the wiring diagram and it looks like the white/black wire is ground. So that's what I'm going with.

 

[ParaJake]

SUCCESS! The motor works when 12V goes directly to it. I definitely heard it run. Now I know what sound I'm listening for anyway. It's reassuring to know that the motor works.

 

[suprarx7nut]

SUCCESS! The motor works when 12V goes directly to it. I definitely heard it run. Now I know what sound I'm listening for anyway. It's reassuring to know that the motor works.

Nice work! Now just need to figure out what's going on with your wiring. With no trouble codes, I am not aware of any other reason the pump would refuse to run (assuming all doors shut, etc..)

 

[ParaJake]

Yeah, I'll have to follow the wiring diagrams and check all the components. Super excited.
I am curious to where the AHC main relay is located. As I said before, there aren't any obvious relays jumping out at me under the steering column. I'm not sure if I'm looking in the right spot or not.

 

[ramangain]

SUCCESS! The motor works when 12V goes directly to it. I definitely heard it run. Now I know what sound I'm listening for anyway. It's reassuring to know that the motor works.

Excellent. Onwards

 

[IndroCruise]

SUCCESS! The motor works when 12V goes directly to it. I definitely heard it run. Now I know what sound I'm listening for anyway. It's reassuring to know that the motor works.

Great work and excellent progress!! At least we know that the AHC Motor and Pump are capable of running. We have yet to discover whether it is delivering adequate fluid volume and pressure but we will get to that later.

Meanwhile, can you please conduct the "Height Control Operation Test" (also called the "Active Test"), not with Techstream, but manually as described in my Post #41 -- and pasted again below and attached for easy convenience. See also Page 6 of the attachment. We now need to know whether this test works or not -- either way, that will help refine the search for the problem:

1. With Ignition OFF, connect terminals Ts and E1 at DLC1 (this is the socket in the engine bay, usually over the RHS wheel arch with the word DIAGNOSTIC on the top cover. The terminal "map" is shown inside this cover. Instead of Special Service Tool (SST) 09843-18020 which is just a piece of bridging wire, find something simple -- I use an unbent paperclip for this test. Voltages are low here low, about 4.5 volts, and will not cause a problem -- but be careful to connect the correct terminals,
2. Turn ON the engine.
3. Push the DOWN button on the Height Select switch within 5 seconds of engine start and hold it down for 5 seconds. There will many flashing lights in the instrument cluster (because the ECU has been by-passed). Ignore these -- they will revert to normal later, after the test, when the bridge (paperclip) is removed and the AHC ON/OFF switch is pressed down for a couple of seconds,
4. Use the combined settings to move front or rear up or down (listen for the operation of the AHC Pump and its motor)
5. When finished, switch OFF engine, then remove the bridge (paperclip),
6. Re-start, push down the AHC ON/OFF for a couple of seconds to clear the test.

 

[ParaJake]

@IndroCruise
Thanks, I will perform this tomorrow if time permits

 

[IndroCruise]

@IndroCruise
Thanks, I will perform this tomorrow if time permits

In addition may I also suggest testing the three AHC controls -- ON/OFF, Raise/Lower and Comfort/Sport -- on the centre console as mentioned in my Post # 49:

• checking the actual condition of the console switch even though there are no DTC indicators -- test details are found in FSM Diagnostics at C1786, C1787, C1788 -- also see pics at Suspension problem even after replacing almost everything - https://forum.ih8mud.com/threads/suspension-problem-even-after-replacing-almost-everything.812905/page-2#post-9444084 -- can be subject to spills of water, coffee, etc.

It is easy to overlook the simple possible problems -- like a previous Owner spilling coffee or soft drink or whatever. If this has happened, there will be corrosion or mess on the switch contacts. It is not difficult to pull the switch assembly and clean.

 

[ParaJake]

In addition may I also suggest testing the three AHC controls -- ON/OFF, Raise/Lower and Comfort/Sport -- on the centre console as mentioned in my Post # 49:

• checking the actual condition of the console switch even though there are no DTC indicators -- test details are found in FSM Diagnostics at C1786, C1787, C1788 -- also see pics at Suspension problem even after replacing almost everything - https://forum.ih8mud.com/threads/suspension-problem-even-after-replacing-almost-everything.812905/page-2#post-9444084 -- can be subject to spills of water, coffee, etc.

It is easy to overlook the simple possible problems -- like a previous Owner spilling coffee or soft drink or whatever. If this has happened, there will be corrosion or mess on the switch contacts. It is not difficult to pull the switch assembly and clean.

Ok, thanks for that. I'll do all those tests. When doing the Comfort/Sport check, will I do this stationary and just watch the fluid level change? Or should I do this with the wire bridge inserted while driving? It's probably a dumb question. I feel like driving while having the bridged connection is a bad idea.

 

[IndroCruise]

Ok, thanks for that. I'll do all those tests. When doing the Comfort/Sport check, will I do this stationary and just watch the fluid level change? Or should I do this with the wire bridge inserted while driving? It's probably a dumb question. I feel like driving while having the bridged connection is a bad idea.

No, defintely not a dumb question – but doing tests while in motion is not our purpose right now.

Suggest do the "Active Test" per notes in Post #88 and attachment while stationary in the garage.

Put the bridge in place between E1 and Ts terminal with ignition "OFF", then sit in the car, start engine and immediately hold down the "DOWN" rocker switch for at least 5 seconds. This puts the system into test mode and a lot of warning lights blink in the instrument cluster because various systems have been by-passed. Now you are in test mode, follow the instructions in the box to move the Front or Rear up or down.

We are particularly interested in the following, with the engine still running:

• for the Front when in Active Test mode, put the console switch into "Comfort" position, AND then press the "UP" rocker switch, and separately,
• for the Rear when in Active Test mode, put the console switch into the "Comfort" position, AND hold down the "ON/OFF" switch, AND at the same time, press the "UP" rocker switch.

In both cases, don't go too far -- do not want to push against the upper limits of the suspension travel, which is why the warning is given in the notes. If it seems to get out of hand or you become uncomfortable, press the "DOWN" rocker switch, or, turn the engine "OFF" and start again.

The main purposes here are to see whether these steps do start the Pump -- which should happen -- and that the relevant Levelling Valve in the Control Valve Assembly does open -- and whether the vehicle does actually rise as it should.

You have shown previously that the Pump and its motor are capable of operating when connected directly to the battery.

If there is no response to the "UP" movement in this "Active Test", then a relay or fuse somewhere in the AHC system is not allowing power to get to the motor driving the Pump. The next steps will be to find the cause – starting with the whereabouts of the AHC Main Relay as mentioned in your request to @Rebus Knebus at your Post #82.

I would say that the grey box in your photo at Post #82 and pasted again below is the ECU, but I cannot see the AHC Main Relay which I thought would be nearby. Also, I don’t understand the empty bracket or holder which is visible on the ECU. Maybe others can assist here????

If there IS a positive response to the "UP" movement in this "Active Test" and the vehicle does rise, then one or other of the ‘fail safe’ modes have locked out the operation of the AHC system during ordinary operation of the vehicle.

I noted a list of 8 possibilities of 'fail safe' mode at the end my Post #49. As mentioned by @suprarx7nut, usually, but not always, these situations are accompanied by DTC which gives a starting point. By way of example, causes may include something as simple as longstanding airlocks in the system or a failed pressure sensor.

Anyway, let’s see what happens with the “Active Test” and also maybe the location of the AHC Main Relay can be identified -- unless it is missing altogether??

Then some next steps can be suggested.

Looking for AHC Main Relay -- pic by @ParaJake

 

[Rebus Knebus]

@Rebus Knebus
I'm having a hard time finding the AHC Main relay under the dash. Looking under there in an extremely awkward angle, there are no relays that are jumping out at me. A LOT of wires and plugs, but no relays. Is the grey box on the far right of this pic the suspension control ECU?

I’ve never had to locate the AHC main relay myself, but I agree with @IndroCruise that the gray box is the ECU and that the empty bracket looks suspicious.

I found an ebay pic of the ECU and a Partsouq pic of the AHC main relay and it looks to me like the relay is the part that’s missing from the bracket. Are there any empty connectors nearby?

 

[IndroCruise]

I’ve never had to locate the AHC main relay myself, but I agree with @IndroCruise that the gray box is the ECU and that the empty bracket looks suspicious.

I found an ebay pic of the ECU and a Partsouq pic of the AHC main relay and it looks to me like the relay is the part that’s missing from the bracket. Are there any empty connectors nearby?

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@Rebus Knebus : Great feedback -- thank you -- the mystery might be becoming less mysterious!!

@ParaJake : Suggest rummage around in the wiring near the ECU and see if a corresponding connector is visible, with or without an AHC Main Relay still attached -- seems like it would have to be in there somewhere.

The Electrical Wiring Diagram (EWD) in the attached document certainly supports the idea that this relay would be close to the ECU.

When found, it will be worthwhile to test the relay as described in the attachment -- or you may prefer to cut to the chase and replace it.

If only the connector can be found with no relay attached, then a new AHC Main Relay will need to be acquired.

After looking at the attached troubleshooting guide, it is clear that the AHC system is not going to work without a healthy working AHC Main Relay! There probably is not much point in proceeding with the other tests mentioned in my previous posts until a satisfactorily working AHC Main Relay is in place.

It seems likely that the vehicle is in the 'fail safe' mode described in the image below. The vehicle may have other problems as well -- and a combination of faults is a possible cause of no DTC's being displayed -- although I must say that I am surprised about this.

Obviously, there are some unknowns in the previous Owners' history with this vehicle. This relay did not just fall out of the bracket. It seems possible that there has been previous work on the relay or the ECU and the relay has been dislodged or removed.

 

[YvesNL]

I'm sorry if this has already been mentioned, I read parts, but not the whole thread, yet.

I had AHC troubles as well, in the end it turned out to be the alternator "L" signal, the "Engine running" signal.
It won't show in the AHC screen on Techstream and won't give you any codes.

It probably will light the "Battery" light on the dash, is that on while the engine is running?
You can find my troubleshooting on this problem here: Hi From The Netherlands & AHC Issues - https://forum.ih8mud.com/threads/hi-from-the-netherlands-ahc-issues.997849/page-3

If you can't find the problem and don't know where to start searching after you've found the main AHC relay I would grab a multimeter and page DI-218 of the FSM.
On this page you will find "terminals of ECU" and also what voltage/signal needs to be on each pin. You can easily measure on the back of the ECU connectors and check if all the signals are OK. If not, you'll have to see why the signal is not OK.

 

[ParaJake]

@IndroCruise and @Rebus Knebus, thanks for the pics and sharing in my suspicion of a missing piece that's supposed to go in that empty bracket attached to the ecu. Im a bigger guy and squeezing my torso into the driver's footwell of the vehicle requires some gymnastics and yoga on my part. I'll take another look later today when I get the chance. I'll look for either a wire harness/connector that's not attached to anything, or the possibility that the relay has been shoved somewhere else up high under the dash. I'll do this before trying the active test with the bridge pin in the diagnostic port.

@YvesNL, the Battery light on the dash is not on. However it may be possible that my alternator is going bad. I have a relatively low reading at 13.5V. Which is enough to keep the battery charged, but should be more like 14.7V.

 

[uHu]

Mystery indeed. Had to have a look under the dash - snapped a few pics of the relay. The part number appears to be 89278-60010 on my 2004-july prod hdj100.
I also found a russian site where someone took apart the relay, which might become valuable if Amayama is right in that the relay is not made anymore.

Google translated russian TLC site

Toyota 89278-60010 (8927860010) RELAY, SUSPENSION CONTROL MAIN

Toyota 89278-60010 (8927860010) RELAY, SUSPENSION CONTROL MAIN. New & genuine Japanese car parts. Fast shipping. Low prices. Request a quote from Amayama Trading Co. online.

www.amayama.com

 

[ParaJake]

Mystery indeed. Had to have a look under the dash - snapped a few pics of the relay. The part number appears to be 89278-60010 on my 2004-july prod hdj100.
I also found a russian site where someone took apart the relay, which might become valuable if Amayama is right in that the relay is not made anymore.

Google translated russian TLC site

Toyota 89278-60010 (8927860010) RELAY, SUSPENSION CONTROL MAIN

Toyota 89278-60010 (8927860010) RELAY, SUSPENSION CONTROL MAIN. New & genuine Japanese car parts. Fast shipping. Low prices. Request a quote from Amayama Trading Co. online.

www.amayama.com

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Great pic. Very useful. Thanks @uHu. I haven't taken a look yet. I wonder, if it is disconnected, if that would throw a trouble code. And if it is disconnected, I wonder what benefits somebody would have by removing the relay. These pics at least give me a plug type to look for tucked under the dash.

EDIT: I did find the part on Amazon using the part number. It says temporarily out of stock. I wonder how "temporary" it will be out of stock.

 

[Rebus Knebus]

EDIT: I did find the part on Amazon using the part number. It says temporarily out of stock. I wonder how "temporary" it will be out of stock.

The part was in stock for my ‘03 on Partsouq, but you should double check the PN using your VIN before ordering anything.

 

[ParaJake]

The part was in stock for my ‘03 on Partsouq, but you should double check the PN using your VIN before ordering anything.

I will definitely do that. But I'm going to try to find the plug first. Maybe the relay is intact and on the vehicle but tucked up under the dash in a less than obvious place.