AHC Removal - Fuses vs ECU (1 Viewer)

[jLB]

So, I finally gave up on my AHC system in my 06 LX470. I had a local shop do the physical installation, of a Tough Dog kit, due to back issues.

Last night, I yanked the 50a under hood "AHC" fuse, the driver side dash 15a "AHC-B" fuse, and driver side dash 20a "AHC-IG" fuse.

Looking at historic posts on this subject, I see older posts that mention "pulling the fuses", and newer posts that mention "disconnecting the AHC ECU". One "disconnect" thread suggests that unless you have "Shaq hands" that you should be able to disconnect the AHC ECU without dropping the under dash panel. I didn't think I had "Shaq hands", but maybe I do.

Looking at the 2006 EWD, I can't see much difference between "pulling the fuses" vs "disconnecting the AHC ECU". If there is a major difference, can someone please clarify the difference?

 

[birch hill]

Only thing you need to do is unplug one plug from ahc computer. Nothing else needed

 

[Beams37]

I'm about to ask the stupid question of the day .... What happens if you don't do that? I mean once the hydro system is removed, what actually happens?

 

[birch hill]

Dash lights would be the result

 

[jLB]

Only thing you need to do is unplug one plug from ahc computer. Nothing else needed

I understand that is an option, but my questions are "If I've already pulled the fuses, and they seem to have the desired result, is there any reason to bother with digging under dash to disconnect the AHC ECU?" and "Is there something (negative) that I've overlooked about pulling these fuses?"

My EWD for an 06 LX seems to indicate the following:

Under hood 50a AHC fuse = Battery power, through “AHC relay”, to pin 2 of connector A14 on AHC pump motor​

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DS under dash 15a AHC-B fuse = Battery power, through “AHC main relay” to pin 13 of connector S6 on AHC ECU​

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DS under dash 20a AHC-IG fuse = Ignition to pin 1 of connector S8 on AHC ECU​

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After pulling the three fuses:

• the green H-N-L lights are gone
• the yellow AHC OFF light is gone
• the little white picture of a truck is gone (this one was a bit of a surprise).

In some earlier posts on this subject, I see mentions of pulling the fuses possibly affecting other circuits (tilt/telescope, and steering angle sensor are suggested), but I haven't been able to find any of these type issues so far...

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[birch hill]

My understanding based on probably the same things you read are pulling fuse disables steering wheel sensor for stability control. I have no proof of it. Unplugging the one harnes did the trick for me without any bad side effects either real or imagined.

 

[MongooseGA]

I pulled the big fuse, I think, from the engine compartment when I did my AHC delete. No idiot lights but the "LOW" light does still blink. I kinda wouldn't mind if that light went away but maybe the white truck silhouette would stay...? Would anyone happen to know if that's possible without modifying anything beyond pulling the fuses, and if so, which fuse specifically only corresponds to the blinking light? Probably a long shot but worth an ask.

 

[jLB]

My understanding based on probably the same things you read are pulling fuse disables steering wheel sensor for stability control. I have no proof of it. Unplugging the one harnes did the trick for me without any bad side effects either real or imagined.

Out of extreme paranoia, I've replaced the "AHC IG" fuse, and shoved my "Shaq hands" up under the dash, eventually working the largest/lowest/closest of the 3 connectors on the AHC ECU loose.

With the 2 fuses (under hood 50a AHC, and under dash AHC-B) and the 1 AHC ECU plug disconnected:

• the green H-N-L lights are gone
• the yellow AHC OFF light is gone
• the little white picture of a truck is gone

I hooked up Techstream to check things out. Techstream was still able to talk to the AHC ECU, and was bitching about "steering angle sensor". I reinstalled AHC-B, and still same. I did the "Shaq hands" thing again and was able to just barely get connector #2 out of the AHC ECU. Techstream now showed the AHC ECU as "unavailable". Reset VGRS steering wheel position, and did a zero point calibration while I was in there.

End result, under hood 50a AHC fuse removed, bottom two AHC connectors removed and 2 AHC fuses replaced.

(God help me, if I've got to cram my "Shaq hands" all the way up to connector #3 and pull it!)

 

[Brian Waag]

I pulled the big fuse, I think, from the engine compartment when I did my AHC delete. No idiot lights but the "LOW" light does still blink. I kinda wouldn't mind if that light went away but maybe the white truck silhouette would stay...? Would anyone happen to know if that's possible without modifying anything beyond pulling the fuses, and if so, which fuse specifically only corresponds to the blinking light? Probably a long shot but worth an ask.

Same with me. IIRC, there is another fuse or relay under the DS dash somewhere that is supposed to stop the "low" blinking green light and disable the white truck silhouette lights. Would love to know where that thing is if that is indeed the "fix".

 

[customcruiser]

I tried all combos and could not get truck silhouette to show up without the blinking off and Lo light.

If you pull the first 20a fuse under the dash while the truck is on you will get just the truck silhouette but it goes way after you restart.

 

[birch hill]

Out of extreme paranoia, I've replaced the "AHC IG" fuse, and shoved my "Shaq hands" up under the dash, eventually working the largest/lowest/closest of the 3 connectors on the AHC ECU loose.

With the 2 fuses (under hood 50a AHC, and under dash AHC-B) and the 1 AHC ECU plug disconnected:

• the green H-N-L lights are gone
• the yellow AHC OFF light is gone
• the little white picture of a truck is gone

I hooked up Techstream to check things out. Techstream was still able to talk to the AHC ECU, and was bitching about "steering angle sensor". I reinstalled AHC-B, and still same. I did the "Shaq hands" thing again and was able to just barely get connector #2 out of the AHC ECU. Techstream now showed the AHC ECU as "unavailable". Reset VGRS steering wheel position, and did a zero point calibration while I was in there.

End result, under hood 50a AHC fuse removed, bottom two AHC connectors removed and 2 AHC fuses replaced.

(God help me, if I've got to cram my "Shaq hands" all the way up to connector #3 and pull it!)

I wonder why unplugging that 2nd harness would have any effect on steering wheel position sensor? Sure it wasn’t plugging the fuses back in that fixed it ?

 

[jLB]

I wonder why unplugging that 2nd harness would have any effect on steering wheel position sensor?

According to the EWD, the connections between VGRS/steering sensor and the AHC ECU are on the first "S6" connector.

I suspect this was less about a "steering wheel position sensor" and more about the AHC ECU was still communicating with Techstream with the 2nd connector connected, but unable to receive expected inputs with the 1st connector removed. After removing the 2nd connector, Techstream was no longer able to communicate with the AHC ECU, therefore the codes that the AHC ECU was throwing for "S6" inputs missing were no longer appearing in Techstream.

 

[takeachance]

What would the results of removing the two fuses (AHC and AHCb) and removing the controls from the dash be? Has anyone taken out the AHC controller from the dash? If so how was that?

 

[Arvin G.]

2000 LX470

I pulled the 50a AHC under the hood and the 15a AHC—B under the driver side. My temp and AC controls stopped working. Put the 50a back in and temp AC worked again. Guess I have to try the AHC ECU again. I must have Shaq hands!

 

[jLB]

Disconnecting the AHC computer on our 99 LX, I have come to the conclusion that "Shaq hands" are irrelevant... You have to have the hands/fingers of a child to reach in there and disconnect it!

I finally gave up, and pulled the plastic panel below the steering wheel, the metal bracket behind that, and the plastic air duct under the steering wheel, in order to disconnect the AHC ECU.

 

[CBeckFJ]

All I did was disconnect the 50A fuse under the hood. AHC diagram on the dash is stuck in high, but no other lights appear.

 

[gamecock2009]

Disconnecting the AHC computer on our 99 LX, I have come to the conclusion that "Shaq hands" are irrelevant... You have to have the hands/fingers of a child to reach in there and disconnect it!

I finally gave up, and pulled the plastic panel below the steering wheel, the metal bracket behind that, and the plastic air duct under the steering wheel, in order to disconnect the AHC ECU.

Hows the tough dog treating you? Mind asking me how much the shop quoted you for the swap?

 

[jLB]

Hows the tough dog treating you? Mind asking me how much the shop quoted you for the swap?

Very well! I've had it in the 06 LX for about a year. There were a few tweaks here and there, fine tuning it after the initial install, but I've been pretty pleased. We just installed our 2nd Tough Dog/Trail Tailor setup, and after our experience with the 06 LX, we made a few minor changes in some of the components that we chose, and its ride is absolutely perfect!

I have no idea. On the 06, I don't recall. On the 99, it was mixed in with a fair bit of other work, trying to prepare for a summer road trip.

 

[Boricp]

Out of extreme paranoia, I've replaced the "AHC IG" fuse, and shoved my "Shaq hands" up under the dash, eventually working the largest/lowest/closest of the 3 connectors on the AHC ECU loose.

With the 2 fuses (under hood 50a AHC, and under dash AHC-B) and the 1 AHC ECU plug disconnected:

• the green H-N-L lights are gone
• the yellow AHC OFF light is gone
• the little white picture of a truck is gone

I hooked up Techstream to check things out. Techstream was still able to talk to the AHC ECU, and was bitching about "steering angle sensor". I reinstalled AHC-B, and still same. I did the "Shaq hands" thing again and was able to just barely get connector #2 out of the AHC ECU. Techstream now showed the AHC ECU as "unavailable". Reset VGRS steering wheel position, and did a zero point calibration while I was in there.

End result, under hood 50a AHC fuse removed, bottom two AHC connectors removed and 2 AHC fuses replaced.

(God help me, if I've got to cram my "Shaq hands" all the way up to connector #3 and pull it!)

Hey, I'm basically going at this right now with so much conflicting information. Fuses? Plugs? I removed the large bottom plug and it appears the results are good. No blinky lights but the AHC still powers on start up. I will remove the tank and unplug it so that's not a concern. But when I removed the bottom plug my telescoping steering went away.
What was your final solution. Plugs? All 3 ? Bottom 2? Fuses?

 

[jLB]

Hey, I'm basically going at this right now with so much conflicting information. Fuses? Plugs? I removed the large bottom plug and it appears the results are good. No blinky lights but the AHC still powers on start up. I will remove the tank and unplug it so that's not a concern. But when I removed the bottom plug my telescoping steering went away.
What was your final solution. Plugs? All 3 ? Bottom 2? Fuses?

On mine, my final solution was to remove the 50 amp AHC (under hood) fuse, and the bottom two AHC ECU plugs.

My tilt/telescope still works, and nothing "funny" is displayed in TechStream.