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Discussion Starter #1 (Edited)
Hiya guys, just did this to my civic. I've got an 08 LX Sedan. Decided to do a write up with pics for anyone that's interested in doing it (Not sure if this will work on an LX coupe tho). It's actually quite simple, the feature itself is already in the car. There are just a few things that need to be done in order for it to be used.

Things you'll need to buy:
  • Blank Key w/4 Button Remote - 35111-SVA-306
  • EX/Si Sedan Powered Trunk Release Mechanism - 74851-SNA-A22 (
  • Multimeter (If you don't already have one)
  • Additional Wiring & Wire Terminals (I had a Civic wiring harness laying around and used wire from that)
  • Male Connector for Powered Trunk Release Mechanism
There are a few other bits you'll need as well but those will be provided by your current trunk release mechanism. Don't worry, you'll see what I mean.

I'd suggest holding off from buying the trunk release mechanism until you get through this first bit right here, just to make sure it's possible for your car.

Once you get your key cut and programmed hold down the trunk release button to see if the light on the remote will blink. If it does then it means the signal is being received by your car. Next remove the Rear Left Bolster to get access to the wiring harness behind it.
Unplug the left side of the connector and let it hang. We'll get to that in a minute.

This bit below will determine whether or not you continue with the project.

Get your multimeter and test pin 4 on the connector that runs to the front of the car by using the trunk release button.

You're looking for a pulse that activates ever time you use the trunk release button then drops back to 0. If this is not the case with pin 4 then test all the other pins as well. If none of the pins give you a pulse of current then your car isn't equipped with the feature already.

Once you've confirmed which pin is receiving the power check the other connector that was left dangling, there should be a blank spot in slot 4 instead of a pin. Pop open the connector so that you can slide your new wire into slot 4 which was previously empty and run it to the trunk. (I chose to run it along side the factory wiring harness, looks much cleaner this way.)
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Now to work on the trunk. Pop your trunk and remove the trunk lid insulator if you have one. You've probably noticed that your current mechanism has a male connector attached to it and that the new powered mechanism has a female port on it. This is ok, we'll be changing that. The two wires running to your current mechanism are connected to a sensor in the latch that tells the car the trunk is open. (This is what causes the dash to indicate the trunk is open and also what tells the cargo light in the trunk to turn on when the trunk is open). From here remove the manual trunk release mechanism and disconnect the connector running from it.

After this, remove the pins attached to the 2 pin connector that connected to the old mechanism. Use the extra green and black wire that you cut and kept to extend the blue wire (power for sensor) and black wire (ground). These pins will be transferred over to the 3 slot connector that you purchased. The wire that you ran to the trunk for the motor will go along with those wire into the 3 pin connector you purchased. With the connector flipped upside down the wires will be connected in this order. Green wire for trunk release mechanism to the left, Black wire for ground in the middle and Green wire for sensor to the right.
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The sensor itself also needs to be changed in order for you to get the functionality back because the sensor in the EX/Si latch and the sensor in your old latch are slightly different.
So remove your sensor from the old latch, and replace your new sensor with it. From here install your new powered mechanism and connect the connector. You should now have remote trunk release and your trunk sensor should also be working.

Finished product, looks pretty good If I do say so myself.
Excuse how nasty my mechanism is. I popped off the cover housing the motor so I can understand what each pin was supposed to connect to in order for everything to work then sloppily glued it back on with some strong glue. You won't have to do that though.

Sorry I couldn't go into more detail, had already done this by the time I decided to do the write up so I didn't get a list of tools needed or more pictures that explained how to remove pins and etc. It's really not that difficult, don't let this DIY fool you! If you're interested in getting remote trunk release for your LX sedan give it a shot.
 

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Discussion Starter #3 (Edited)
Thank you for the DIY! Will be trying it out soon. Aren't LX's supposed to come standard with this feature?
Not that I'm aware of no. Not for the 8th generation at least. As far as I'm aware EX and up have the Power Trunk Release. Anything under it would only have the Manual Trunk Release.
 

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Sorry to revive an old thread, but can anyone clarify the purpose of moving pin 12 to pin 4? It seems illogical to be simply moving the connection to pin 4, are you breaking a connection(as far as i can see pin 4 is empty on both sides) or is there something special about the specific slot within the connector?

If i can get this working i will post my own write up with as much detail as i can
 

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Discussion Starter #6
Sorry to revive an old thread, but can anyone clarify the purpose of moving pin 12 to pin 4? It seems illogical to be simply moving the connection to pin 4, are you breaking a connection(as far as i can see pin 4 is empty on both sides) or is there something special about the specific slot within the connector?

If i can get this working i will post my own write up with as much detail as i can
Hiya, OP here. The connector that runs to the trunk doesn't have a pin in slot 4, meaning slot 4 doesn't have a wire going to the trunk. But on the connector that comes from the front of the car, slot 4 actually houses the pin that sends the signal for the remote trunk release feature. The wire that we are utilising from the key hole is in slot 12. To be able to use the remote trunk release feature you'll have to relocate pin 12 to slot 4 in order for the Powered Trunk Release Mechanism to receive that signal since the wire from the Tailgate Cylinder Switch is being relocated to the Powered Trunk Release Mechanism. You are correct, the connection originally running through pin 12 from the front is being broken. Originally that ran to the Tailgate Cylinder Switch (which I originally thought was just a blank), and I have no idea what it's purpose was. Possibly has something to do with the alarm system but I never contacted Honda to find out. I haven't experienced any problems so it shouldn't be a problem.

This DIY was done in a way where I wouldn't have to run new wires, or buy the connector for the Powered Trunk Release Mechanism seeing that the connector on the Manual Trunk Release Mechanism is a different shape and only accommodates 2 wires. If you'd like to do it better than I did I'd suggest purchasing the connector for the Powered Trunk Release Mechanism (PN I believe is 04321-SM4-409), run new wiring from slot 4 since it's blank to that new connector and extend the original wires that ran to the Manual Trunk Release Mechanism because they are too short. This way the harness running to the Tailgate Cylinder Switch will be left alone, and you'll have the remote trunk release feature as well.
 

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Well thanks for the clarification. I appear not to have the power release or i might have just been looking at it wrong. I have the canadian lx coupe and ill have to inspect again closely.. as its really hard to see inside that panel without removal.. As far as i know the tailgate cylinder switch is indeed a part of the alarm, and causes the alarm to go off when the trunk latch is forced open without a key being inserted
 

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Well thanks for the clarification. I appear not to have the power release or i might have just been looking at it wrong. I have the canadian lx coupe and ill have to inspect again closely.. as its really hard to see inside that panel without removal.. As far as i know the tailgate cylinder switch is indeed a part of the alarm, and causes the alarm to go off when the trunk latch is forced open without a key being inserted
If it's an LX it doesn't have the Power Trunk Release Mechanism because that's only available on the EX and up. Our LX's come with the Manual Trunk Release Mechanism. Before you purchase any parts I'd strongly suggest checking your harness to see if there is a wire running to slot 4 from the front of the car. If not then it might not be possible (this way at least) for your car, you can try testing each pin with a multimeter by pressing the trunk release button on your remote to see if maybe it's in a different slot for the coupe's. This DIY was made for sedan's, unfortunately I'm not sure if it would work for the coupe's.

I decided to ask my local dealer here in The Bahamas about the purpose of that harness running to the Tailgate Cylinder Switch, they told me they had no idea what I was talking about. It's the only dealership here in The Bahamas so I had to contact dealers in the US and I contacted about 4 of em before I gave up since they too didn't know what it's purpose was. One of them said it sends the signal to the dash to notify you that the trunk is open which is incorrect because the Trunk Release Mechanism itself does that. And the rest asked me to bring my car to the service department to have it looked at in order for them to assist me further which would require me shipping my car overseas so that's out of the question.

I appreciate you letting me know what it's purpose is. Now I'll redo the whole job and run new wires to have my remote trunk release work while keeping the harness running to the Tailgate Cylinder Switch. Also, as soon as I get it done I'll redo this entire DIY so that it's done the right way without cutting corners.
 

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Discussion Starter #9
Post has been updated for the install to be done correctly. Apologies for the earlier version.
 
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