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My Quest - retrofit Tailgate Handsfree Assist to an Aspec- need help
I swear I just don’t understand why Honda does this...
New 2021 Aspec, I really want HFA.
So - studied the installation instructions.
I searched high and low here on AZ.
Wasnt a lot of info out there.
The basics seemed to be the only reason HFA wasn’t compatible with the Apsec was the rear under spoiler was more svelte and the radar sensor wouldn’t fit.
So I took a bet. Turns out they sell a smaller sensor for vehicles with the tow hitch. I found one of each sensor relatively cheap on eBay and decided I could hack up the plastic carrier for the sensor and wedge it in there.
It’s just a sensor right?
I chose to use the full length sensor, as this gives you more accessibility to use the feature. I wedged it in on the drivers side between the outer bumper skin and the aluminum frame supports. It’s a little hacky, but I expect it’ll work great provided the presentation angle is consistent with specification.
I’ll snap a pic of this once I can show it works.
Here’s the next challenge, one I didn’t expect.
The HFA installation is prewired to plug into and accessory harness in the drivers rear quarter panel. This is the same harness you plug the trailer hitch harness into.
I have the trailer hitch, had it dealer installed at purchase...
So I tear into this today, finding the 8 pin connector noted below, and the trailer hitch accessory harness already plugged in. At first glance I think, shit, I need a Y-splice connector set to use both accessories.
but... I look harder at both sides of the harness connectors and note the 2 pins are blank on both the 8 pin accessory harness AND the added trailer harness. Looking at the HFA harness, these are the 2 pins I need...
F$CK.
So, on the ASpec, the 8 pin connector is ONLY wired with 6 wires, leaving the 2 connectors blank that would connect to the HFA harness!!!
But Why?!?
So... I went ahead and finished the install. Drilled the hole for the button, ran the harness in etc... this wasn’t difficult as the instructions make it, you can do most of it by only loosening the rear panels.
Here’s what I need:
Anyone around here an Acura tech? Or have access to wiring diagram?
I need the wiring pin outs of the 8 pin accessory harness to know what the missing 2 wires lead to. The HFA harness only has 3 wires - red/purple that are in the female 8 pin connector, and a body ground.
I suspect red/purple is any 12v+ and a digital signal wire that the sensor tells the ecu to open the tailgate... but what do I know.
If someone can tell me what those 2 missing wires in that 8 pin accessory are, and give me some pointers on where I could tap them in the main harness - I’ll crack the code on this and share the results.
Pics below:
- Instruction page from install manual, location of “8 pin accessory harness” in drivers side rear fender well
- eBay RDX full size HFA sensor that goes in the bumper
- my 8 pin connector, showing the location of the missing 2 pins, which happen to be the exact location of the red/purple wires of the HFA harness.
Let’s figure this out!
It can retro to ANY RDX except the ASpec.
I studied the installation manual, and
Tanks for pioneering this. I have thought about adding the sensor to my A-spec, and now I know what to expect. Precision crafted engineering at its best again.
I suspect the wires go into tailgate controller (74970-TJB-A02), perhaps you can take a look there if no wiring diagram is available.
Thanks- it’s 2 wires, we can figure this out.
That’s helpful.
I would hope I could get 2 pictures from someone with a non aspec (tech package required I assume).
can someone pull their drivers side lower cargo area cover and get - couple of photos:
- the 8 pin accessory harness this HFA harness/tailgate harness connects into.
I’m looking to see the color of the wires that should be in the pin positions but aren’t in the ASpec.
- the tailgate control module sonyfever references above wiring harness. I want to see if there are missing wires in that harness as well.
From the schematic, HFA red cable needs to go to power tailgate control unit B10, and the purple cable (HFA control signal) goes to A13. B10 is labeled as +B_BACK_UP and seems like a power source.
Kennedy. Aloha! I also got a 21 RDX Aspec and I ran into that problem. I actually ordered the HFA for the wife's RDX car. It came in and I was scheduling it with the dealer then they tell me they cannot do it because it is not compatible and could cause issues. So, the install was cancelled and I got refunded my money. But I really think it can be hacked and it'll work. You're right. Wonder why our beloved Honda/Acura manufacturers opted not to pre-wire or enable this option for our 21 RDX Aspec. Sucks. So, if you don't mind. If you figure it out, please send me instructions and also pictures on how you done it. Also, where you bought the HFA kit or that smaller sensor that you mentioned. We need to work this out for the team Acura RDX. Yeah, fine engineering at it's finest. So, standing by with your next post.
Aloha again! Can anyway tell me what the A13 wire is? The B10 power tailgate control unit. Did anybody get this successfully installed? Anyone? Would appreciate any inputs, hacked instructions, photographs (outside and underneath the car and of course the wiring) Thanks Team RDX?
Thanks Sonyfever. I guess we'll just have to wait until some post a successful hack for the HFA. Dang why would Honda do that? Someone, please post it and let us know.
On the tree view, click "Body"->"Power Tailgate", the right-side window will display the schematics. Find "Power Tailgate Control Unit" along the top of the window.
Once you locate it, you can:
1. Double-click on the block, and a window on the right (called "Details') shows you where the control unit is.
2. Locate the purple A13 line, click on the small rectangular box between the lines and the control unit block, and the "Details" window shows you where the pin is located in the connector.
Sonyfever. Aloha! Thanks partner. Unfortunately, the link some how do not work for me. Tried it several times with several computers. Kept saying "file not found or been deleted". Link could be broken or corrupted. Anyway, maybe you can download (or cut n paste) the schematic info and upload here to help all of us.
Haven't heard from Kennedy. Hope he is doing well and have success to report with his 21 RDX Aspec HFA hack. Hopefully, he'll login and update us.
Stay safe out there. Keep in touch. Go Team Acura!
Good news, the Body Control Module is indeed wired for the HFA signal, I will confirm if the wire is pinned on the tailgate control module side in the trunk sometime this weekend. It is likely that it is though, I doubt the wire would run to nowhere. If its there then it should be as simple as tapping the A13 and B10 wires into the 8 pin connector. I've attached photos that I took of the Body Control Module and the connector showing the Purple Wire on the G Connector.
So with the 2022 Advance A-Spec model being available this means there should be a kick sensor that is designed for the A-Spec rear bumper now. I was going to hack the short sensor in but I think I'm going to wait until parts for the 2022 are available to buy.
No progress from me-
the 8 pin in the trunk is missing the 2 wires. I have been unable to figure where to run them too…
I don’t think the 2022 advanced will afford new parts to install this. This issue is there is literally 2 wires missing on the run from the Tailgate control module to the 8 pin connector… I can’t find the tailgate control module to mock up a test…
im reviewing these updates. If anyone here can point me to the TCM location I’ll give her a go again.
I firmly believe the ONLY reason this is incompatible is:
the rear ASpec bumper has no mount point for the sensor. I just wedge/zip tied that bitch in there. In fact, I learned there’s 2 options, a standard “big one” and a shorter one to accommodate the tow hitch. I got the big one horned in with the the tow hitch.
if someone can point me to where the red and purple wires run from the 8 pin to the TCM I’m betting this will work. Where is the TCM?
Kenny, if you read through my previous post I document the exact pins needed to be tapped into. I haven’t purchased anything yet as part availability for the 2022 year is still not available and I’d like to purchase the A-Spec Advanced specific sensor.
Let me dig through the documents I downloaded for a diagram of where the TCM is.
This is about as much info as I can find regarding what the TCM looks like and approximate location. I unfortunately didn’t download more diagrams when I had access to the RDX service manual.
In the last photo you can see the same module with the square sticker high up in the quarter panel.
What am I looking at in this last picture? I think I can see the module in question, in the upper left.
is they mat the inside left REAR quarter panel?
there are affected 2 wires in 2 wire runs here:
from the body control module unit to tailgate control module - you have confirmed the wires depart the body control unit under the front dash, and they are likely run to the “receiving end” of the tailgate control module in the pic above.
Then departing the TCM there is a power “splice” and purple sensor wire from the tailgate control to the dangling harness this kit connects to. I’m my pic above, these are the 2 wires wires missing from that harness.
So this may be simple as running 2 wires from this box to the dangling harness the sensor connects to. This assumes we don’t have to replace the TCM. Can anyone confirm the a tailgate control module is the same PN on the ASpec vs Advanced?
That would suck if Honda actually made a separate TCM that doesn’t allow for the HFA functionality. But I would also be shocked if they did. From my experience Honda likes to create a lot of different part # for the same part.
We’re getting close though. If you have a PayPal or CashApp I’ll buy you a beer for your work.
Also I have no idea why I never attached these photos before. Here's the diagram for exactly where the two cables you need to splice are: A13 and B10. Also in the last photo attached that is indeed the TCM with the part # for the A-Spec, and if you look closely at the A connector you can see the A13 purple wire on the connector on the remainder of the pigtail. The resolution gets pretty bad on the uploads but I can see the A13 wire very clearly.
I can't see if there is a B10 that is on the connector for this A-Spec specific TCM but according to the diagram B10 is a backup for B5. So we should be able to use the B5 wire if there is no B10 present.
@mbnderek
We are about to figure this out. Or things are about to get complicated.
What year is your RDX?
I got to the TCM on my 2021 ASpec today and took some pics.
Remember- I “think” we’re looking for 2 wire runs:
from:
BCM to TCM
From TCM to accessory plug
Would this imply an “input” from the BCM to the TCM AND an output from the TCM to the plug (A13).
You confirmed the BCM wire is there, so it either terminates dead downstream in a harness connection or is the input at the TCM under one of the other CAN labels.
I got to the TCM and took a pic of the connectors:
Let’s start with the HFA signal wire.
Nope- a13 is not present in the harness in the TCM (21 ASpec). So, I see several next steps here:
1) Confirm BCM part numbers are the same between ASpec and Advanced. The software logic for this may/may not be present between both BCM and TCM modules. I’m worried most about that. It look like quite a chore to swap the BCM. If you have to run wiring and swap 2 modules for this… Ugh.
2) Confirm again the BCM wire is there. Can you show me the BCM pinout like you did for the TCM? If it is there, research where the BCM wire terminates. If it terminates at A13, that means as designed that it is likely a CAN signal and there is a splice somewhere in the original harness that runs to both A13 and the dongle.
Under this assumption… Since there’s no run to A13, a splicing the HFA wire on the BCM under dash and run to the A13 AND the dongle.
TCM swap requirement is still in question.
I need the PN for splice wire termination for the TCM connector and the Dongle connector (or I can splice direct for that one)
I’m PMing you my cell. You seem as determined as me to figure this out.
I’ll be leaving the back panels “loose” for a few weeks while we sort this.
Both B5/B10 power wires are present at TCM, so easy splice there.
Whil I was feeling froggy- I went ahead and took a look at the BCM.
I pulled the plug, unfortunately mine is NOT pre wired for HFA. Without pulling the plug (which is a f!cking chore!), it’s really difficult to tell from under the dash.
With that I see 3 options.
- if we’re lucky, add purple wire at BCM, run to TCM and splice dongle.
- maybe have to replace TCM- assume that doesn’t break other shit
- maybe have to replace BCM - assume that doesn’t break other shit
Im willing to pilot option 1-2 with continued parts help/cosponsor . I ain’t replacing the BCM, I’ll think trade in before that…
pic below shows the plug/pin out of BCM missing purple wire:
If the TCM supports it, this isn’t bad. anyone have the PN for the wire connector leads (that go into the BCM/TCM harness plugs?
as much of a painful chore it is, I’d give it a go if I can figure out the connectors
The part diagrams show the wire harnesses are sold in bundles (floor, roof, engine bay, etc etc). Thus the price is really expensive when we only need a few wires out of a bundle. Probably you can get a generic wire to plug into the empty slot on the BCM connector?
From my experience repinning other honda harnesses, the BCM should be an easy process to add the wire. Kennedy and I are currently trying to find the connector type so we get the right pins to add the extra wire.
Update for anyone following along with this process. Kennedy and I have identified and ordered the connector female pins to add the HFA signal wire from the BCM G24 to the TCM A13. Then A13 will be tapped for the HFA module. We will be following the wiring diagram below.
I got some pins from mbnderek (thanks dude) and connected/soldered them onto some 20 gauge wire.
I took the dash apart, and pulled the BCM connector. It was a total bear to get the locking block to release from the connector while under the dash, NOT doing that again.
Got the pins in (pretty sure i got them set right) and ran that wire from BCM G24 to TCM A13, tucking the wire along the lower door sill trims.
I then spliced that wire and ran it to the purple wire in the retrofit kit connector (didn’t have the right connector terminal for that, so just spliced it in).
I then spliced a wire from A10 to the red wire in the retro kit. I confirmed that wire was hot.
Tried it several times, uses the on/off button etc. NO ACTION.
Last stop is to buy/replace the TCM with this PN: 74970-TJB-A02 - anyone tracking this thread have access to one of those help a brother out!
I suspect the TCM doesn’t have hardware or software to support this feature. Lord I hope so. Why Honda would go to such lengths to exclude this feature has to cost more in manufacturing differentiation…
Update: snagged a 74970-TJB-A01 TCM on the bay for $60.
fingers crossed.
would be awesome if the TCM control the UI software and allows you to control the HF kit via the Navi vs the button provided and installed in the retro kit:
04-30-2021, 05:06 PM
