AHC wont raise after battery out (1 Viewer)

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A friend is out of state looking for some help diagnosing an AHC issue. Took the battery out, put it back in and the AHC wont raise. Blinks twice when you try to go from L to N then stops and nothing happens. Is there a calibration procedure for the AHC? or is he looking at a hardware failure?

If there is anyone near Ellensburg Washington with Tech Stream, you could potentially be a life saver.
 
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Dec 2, 2015
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Try a manual clear: ignition off, short Tc and E1 in dlc1, ignition on and push brake pedal 9 times in less than 3 seconds. IG off, remove short.

Took the battery out, put it back in and the AHC wont raise. Blinks twice when you try to go from L to N then stops and nothing happens. Is there a calibration procedure for the AHC? or is he looking at a hardware failure?

If there is anyone near Ellensburg Washington with Tech Stream, you could potentially be a life saver.
 
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Dlc1? I have a gx and 80 so I don't know the 100 series beta.

Okay diag port. Is it in the same location as the 80? Under hood near wiper motor on ps side?

Do you have a pinout diagram?
 
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Under the hood, passenger side, upper fender, about half way back. Once you open the cover everything is marked and labeled. I can get a pic tomorrow.

Jim
 
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A friend is out of state looking for some help diagnosing an AHC issue. Took the battery out, put it back in and the AHC wont raise. Blinks twice when you try to go from L to N then stops and nothing happens. Is there a calibration procedure for the AHC? or is he looking at a hardware failure?

If there is anyone near Ellensburg Washington with Tech Stream, you could potentially be a life saver.

A long way from Ellensburg Washington, but suggest first ensure that AHC is ON. If OFF, turn AHC system ON by pressing and holding down OFF switch on centre console.

Then as mentioned in earlier replies, suggest start by clearing old Diagnostic Trouble Codes (DTC’s) stored in ECU memory so as not to be confused with old events. Existing faults then will show as new events.

To do this, see part way down second page of attachment, at paragraph 1(d), to see diagram of DLC1 showing pins E1 and Tc. (DLC1 is the covered socket in the engine bay, usually with the word “DIAGNOSTIC” on the lid, located as mentioned by @jahawk).

In case of not using handheld tester (meaning if not using Techstream), clear Diagnostic Trouble Codes (DTC’s) in the following way:

  • with Ignition OFF connect terminals E1 and Tc at DLC1. (Note: “SST 09843-1820” is simply a bridging wire. Unnecessary. An unbent metal paperclip is just as good – voltages here are low, around 4.5 volts, but precheck with multimeter if concerned),

  • Turn Ignition ON (without starting engine), ignore dashboard lights,

  • Depress the brake pedal 8 or more times within 3 seconds,

  • When done, remove connector between E1 and Tc,

  • DTC’s are now cleared but will return if faults remain.

After that, it gets more ‘interesting’ – but do the easy, basic things first, such as check (including pull and inspect) AHC fuses and relays.

If necessary, go to AHC Diagnostics section of the Factory Service Manual (FSM) for more information -- see
https://lc100e.github.io/manual/, then use index tabs: Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL & SKYHOOK TEMS
This covers details for the AHC system which is the same on both LC100 and LX470.

Techstream is important to discover DTC's -- there are methods without Techstream ("without handheld tester" per FSM) but these are very long-winded methods and would try the patience of most people.

As a starter, make sure that power actually is getting to the AHC Electronic Control Unit (ECU) and that wiring harnesses and connectors throughout the AHC system are at least free of obvious visible damage.

If necessary, methodically check resistance, continuity and voltage responses as indicated for various components where fault conditions (DTC's) are indicated or suspected.
 

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Joined
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Brisbane, Australia
I just talked to him. Says he thinks its because he loaded a trailer up with the battery out, so the ride had been forced down. Im pretty sure if he unloads the trailer and resets the system he's going to be fine.
Suggest consider the load limits of the AHC system – see guidance in a good general description of the AHC/TEMS system and how it works including load limits at this link:
https://lc100e.github.io/manual/
then follow tabs at top LHS of opening page: New Car Features > CHASSIS > Suspension > Active Height Control Suspension & Skyhook TEMS.

If the attached trailer causes overloading of the AHC system, then the symptoms will be exactly as described in your Post #1 in this thread.

Solution is either less load, or, replacement rear springs with higher spring rate such as KINGS KTRS-79 to carry more load on a permanent basis, or, install inflatable airbags inside rear coils for use with occasional loads -- there are many IH8MUD threads which discuss these options.
 
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Also check the fuse I spent a lot of time and money trying to diagnose a non functioning pump and it just turned out to be a fuse.
 
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Several people have already mentioned jumping E1and Tc already, but that's what worked for me. I was a little intimidated by the process when I was reading about it and not having a full understanding of what exactly I was accomplishing. But it was simple and it worked immediately. Of course, whatever generated the code to begin with still might be an issue and might generate the same code again sometime so it's probably worth looking into it more so you're not just putting a bandaid on a bullet hole. But if the goal is just to get it working today I'd try that.
 

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