LX 570 Easy access AHC (1 Viewer)

[Bryanmc]

This is wonderful help, thank you so much.

If I’m doing this right, I’m seeing 7.9-8 Ohms on each pin. This reading is the same on the rear right harness and the rear left. I haven’t checked the front actuator connectors as they are more difficult to get off with my sliders in the way. Not impossible but not tonight.

So what’s that telling you?

 

[lx200inAR]

This is wonderful help, thank you so much.

If I’m doing this right, I’m seeing 7.9-8 Ohms on each pin. This reading is the same on the rear right harness and the rear left. I haven’t checked the front actuator connectors as they are more difficult to get off with my sliders in the way. Not impossible but not tonight.

So what’s that telling you?

I might be mis remembering the expected resistance. Seems pretty normal to me, I’d be more worried if there was a short or open circuit. What about the ground pin on the wire side of the plug? That would be my first suspect.

 

[Bryanmc]

I bought the FSM just before you posted and it shows the resistance should be between 12-13.6.

So I don’t know if I’m doing something wrong or if there’s something bad prior to the actuators (I guess that might be the ECU?).

I am a novice here, so just to confirm, should I be testing the pins on the actuator itself or the female harness connector? I was testing the harness connector.

Be gentle.

 

[lx200inAR]

I might be mis remembering the expected resistance. Seems pretty normal to me, I’d be more worried if there was a short or open circuit. What about the ground pin on the wire side of the plug? That would be my first suspect.

Also, to be clear, the resistance should be measured across the pins on the actuator, not the truck wire harness back to the suspension ecu. At least, until you can disconnect the harness to the ecu. I don’t know if checking those to ground is bad, but the FSM doesn’t say to.

 

[lx200inAR]

I bought the FSM just before you posted and it shows the resistance should be between 12-13.6.

So I don’t know if I’m doing something wrong or if there’s something bad prior to the actuators (I guess that might be the ECU?).

I am a novice here, so just to confirm, should I be testing the pins on the actuator itself or the female harness connector? I was testing the harness connector.

Be gentle.

See above. The only thing in the harness you want to check is pin 2 to ground.

 

[Bryanmc]

Ok, thanks for the guidance. Will check the actuator itself.

 

[AnyMal]

Mine is pretty slow and inconsistent so I like to lower it manually. The system doesn't lower until a few scenarios are met, but even then, sometimes it lowers and sometimes it doesn't. Usually when I get to a destination people open their doors way before the system has a chance to do anything so i just lower it manually when I'm slowing down to below 7mph.

They always do that! Wish i could disable the door parameter, specially the trunk as @tbisaacs said.
I get it, since the door frame may crush on a curb or something but peoples instinct to rush out wins.
They will also still smash your door carelessly but you cant fix that so easily LOL.

 

[Bryanmc]

Well, I tried and tried to get a read on the actuator with the multimeter but it’s in just a really tricky place. I even took the wheel off and still had a tough time getting the probes in the right place.

I suppose I’ll take it to the Lexus dealer and get their assessment and then figure out if I can do the work.

 

[lx200inAR]

That sucks. So the ground pin in the harness is fine?

FWIW, the FSM basically says check the cables runs between the actuator and the suspension ECU and if that checks out, start replacing parts. Actuator and Suspension ECU being the key parts.

 

[Bryanmc]

Forgot to check the ground pin in the harness.

Remember, I’m an idiot. Can I use the frame as the ground or do I have to reach the negative terminal on the battery?

 

[lx200inAR]

Forgot to check the ground pin in the harness.

Remember, I’m an idiot. Can I use the frame as the ground or do I have to reach the negative terminal on the battery?

Frame should be fine. You might check where you decide to use as the test point to verify it's a good ground (not too much paint or undercoat). I'd just pick wherever looks good and do your test. If the test shows ground to the pin is good (continuity between pin and frame) then you are done testing and have to find something else that is wrong. If it fails, then I'd doublecheck that your test point is a good ground. If that passes, then you found your issue.

 

[Bryanmc]

Pin checks out as grounded.

 

[lx200inAR]

Pin checks out as grounded.

Well...on to next thing. Maybe your difficulty getting to the actuator is why the FSM doesn't suggest testing that connection. If you don't want to try dealer first.

First thing i would do is reconnect the actuator and reset the DTC and see if all the messing around you've done has resolved anything. It does seem convenient that you recently did a flush. Although, you said you aren't 100% sure this wasn't like this before that.


The next step is getting to the suspension ECU. It's behind the rear quarter panel on the drivers side i believe. FSM says to disconnect the connector form the ECU and from the actuator and put your tester leads on to either end. You will probably need some sort of extension or a helper.

To do test (disconnect both the ECU and the actuator plugs):
Step 1
From the ECU end, check the 4 pins in the harness going towards the actuator to make sure none of the pins are grounded (FSM calls this resistance > 10kOhm).
Step 2
From the ECU end, check the 4 pins for continuity end to end by putting one test lead on the ECU side and one on the actuator side (FSM calls this resistance < 1Ohm).
Step 3 (reconnect the actuator plug)
From the ECU end, test each of the 4 leads to ground. Should see 12 to 13.6ohm.



Steps 1 and 2
Standard Resistance:
for RH (C1733)
Tester Connection Condition Specified Condition
K31-4 (RBR-) - N5-3 (RBR-) Always Below 1 Ω
K31-4 (RBR-) - Body ground Always 10 kΩ or higher
K31-5 (RAR+) - N5-1 (RAR+) Always Below 1 Ω
K31-5 (RAR+) - Body ground Always 10 kΩ or higher
K31-13 (RBR+) - N5-5 (RBR+) Always Below 1 Ω
K31-13 (RBR+) - Body ground Always 10 kΩ or higher
K31-14 (RAR-) - N5-4 (RAR-) Always Below 1 Ω
K31-14 (RAR-) - Body ground Always 10 kΩ or higher
N5-2 (E RR) - Body ground Always Below 1 Ω <----------You already did this one

Step 3
Standard Resistance:
for RH (C1733)
Tester Connection Condition Specified Condition
K31-4 (RBR-) - Body ground Always 12.0 to 13.6 Ω
K31-5 (RAR+) - Body ground Always 12.0 to 13.6 Ω
K31-13 (RBR+) - Body ground Always 12.0 to 13.6 Ω
K31-14 (RAR-) - Body ground Always 12.0 to 13.6 Ω

 

[Bryanmc]

Can’t tell you how much I appreciate the help!

Probe extensions ordered.

 

[grinchy]

Did you already unplug the battery for 30 min @Bryanmc ?

 

[Bryanmc]

Did you already unplug the battery for 30 min @Bryanmc ?

No, is that to force a reset or something?

 

[grinchy]

Yes, it puts all the computers back to square 1. Useful for theses out of nowhere errors.

 

[Bryanmc]

No change after disconnecting the battery for about an hour. Today's mission is to find the ECU. I found where it is on a diagram (right where lx200inAR said it would be), but not sure yet how to access it.

 

[lx200inAR]

No change after disconnecting the battery for about an hour. Today's mission is to find the ECU. I found where it is on a diagram (right where lx200inAR said it would be), but not sure yet how to access it.

In this video the guy is unplugging it. He doesn't pull the plug out, so i'm not sure if there is enough slack ( i assume not) to get at the plug and test without removing the whole trim panel. But gives a very good idea of where it is.

How To: LX570 AHC Disable, 20 MPH H Override

This solution stems from all the knowledge that was contributed in @turbo8's thread. With a couple of simple switches you can disable the AHC (essentially locking the truck in whatever height you desire) This will allow you to drive in H over the 20 mph restriction. To me the benefit is...

forum.ih8mud.com

 

[Bryanmc]

Awesome, quite accessible. Thanks!

Interesting stuff in that thread.