HOW-TO: DIY Kill Switch for JK Wrangler - JeepForum.com
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post #1 of 20 Old 10-15-2015, 12:18 PM Thread Starter
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HOW-TO: DIY Kill Switch for JK Wrangler

A hidden kill switch is great theft deterrence - even if someone manages to get your keys, they still wonít be able to start the Jeep. Itís an easy DIY on the cheap, total time is something like 30 - 45 minutes.

Things to buy

Tools needed:
  • A soldering iron and solder, or good quality wire crimps and crimper.
  • Wire cutters / strippers.
  • Electrical tape.
  • A drill and drill bit to mount the switch someplace



Overview:

Weíre going to use the Clutch Interlock Signal to stop the Jeep from starting unless a hidden switch is pressed. You can wire it so the switch AND the clutch must be pressed for the Jeep to start, or so that only the switch must be pressed. I personally chose to wire it so that only the switch must be pressed because Iím used to vehicles that donít have clutch interlocks - with it in neutral, and the e-brake on, obviously.

NOTE 1: Cruise control will no longer disengage when you press the clutch after doing this modification. If you regularly disengage cruise with the clutch (I never do), maybe you shouldnít do this mod.

NOTE 2: The Jeep ignores the clutch interlock signal when in 4LOW. Therefore this kill switch will not function when the Jeep is in 4LOW. (We could modify the wiring on that relay too, I just donít think itís worthwhile)

Step 1:

Locate the third connector on the Powertrain Control Module (PCM) - this is the plug closest to the engine (on the right when looking towards the front of the Jeep)
Unplug it, and pull back the covering on the wires to find the Yellow wire with Orange stripe.



Step 2a (switch and clutch):

Cut the Yellow/Orange wire, and join wires to each end - those wires will run to your switch, so that when the switch is pressed, the signal from the clutch being depressed will reach the PCM, and the Jeep will know the clutch is in, and will start.
When the switch is not pressed, the signal from the depressed clutch will not reach the PCM, and the Jeep will not start.

Step 2b (switch only):

Cut the Yellow/Orange wire, and join a wire onto the end going into the PCM plug. This wire will run all the way to your switch, along with another wire that will go to ground. When the switch is pressed, the circuit will complete to ground, and the PCM will think the clutch is depressed, and the Jeep will start.
When the switch is not pressed, the PCM will not see the clutch as being depressed, and the Jeep will not start.
Tape up the other end of the yellow/orange wire and ignore it.
Connect the second wire to ground - there are multiple options right there near the PCM on the side of the fender.

Step 3:

Run these two wires into the cabin - the best place to do this is using the factory grommet in the very top edge of the engine bay, that has the washer fluid line for the rear wiper. Pull the trim panel off the inside of the Jeep footwell next to the driver, and pull out the grommet.
Poke a small piece of strong wire through from the engine bay until you can grab it down in the footwell. Tape your wires to this and pull them through.
If you donít have plastic ďspaghetti tubingĒ to put the wires in, at least wrap them in tape to protect them from rubbing. Run them through the hole in the middle of the grommet so they donít rub on the edges of the hole in the firewall.



Step 4:

Find a place to mount your hidden switch. Obviously Iím not going to show you where I put mine, because that defeats the purpose. Take your time and find a spot that works well for you.
A couple of things to think about:
  • Likely youíll be turning the key with your right hand, so you want it somewhere you can reach with your left, unless you want to be a contortionist to start the Jeep.
  • Try to get it out of sight, and also not in a place that can be easily ďfeltĒ. If someone were to run their hands under the panel at the bottom of the steering wheel would they immediately find your switch?
  • Do you want to put the switch somewhere you must be sitting in the drivers seat to reach? Or would you rather be able to stand outside the Jeep?
  • Lots of the panels near the steering wheel flex quite a lot when pressedÖ. If you mounted the switch behind one of those without cutting a hole in the panel, you could just push the panel in the right place, which would flex enough to press the switch, and nobody would ever know itís thereÖ
  • Be creative!
Wherever you choose, run your wires to that spot, drill a hole of the correct size in whatever panel needs it and mount your switch.
Connect your switch to the two wires, and make sure you completely hide all the wiring behind trim panels.

Step 5:

Test out your new hidden kill switch. You will have to hold down the switch for the duration of the time you are starting the Jeep - once itís running you can let go.

I also wrote up this HOW TO on my website - http://theroadchoseme.com/diy-jeep-w...jk-kill-switch

-Dan

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post #2 of 20 Old 04-20-2016, 06:50 PM
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Any suggestions for the automatic? I had this on my TJ (manual) but am in the process of purchasing a JK and need to do the kill switch for when I'm out on a backpacking trip.
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post #3 of 20 Old 04-20-2016, 08:04 PM Thread Starter
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Quote:
Originally Posted by tecumsa View Post
Any suggestions for the automatic? I had this on my TJ (manual) but am in the process of purchasing a JK and need to do the kill switch for when I'm out on a backpacking trip.
I looked into the wiring diagrams, and the way the computer senses which gear the auto is in is a complicated beast.
I would not want to mess with it.

If I had an auto, I'd look at putting a switch in some other relay. Maybe the fuel pump, or maybe the ASD relay (auto shut down).

-Dan

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post #4 of 20 Old 04-21-2016, 03:24 AM
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A good in theroy idea,but if they want your Jeep it will be gone in 30 seconds or less.
Most car thief's are professionals.

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post #5 of 20 Old 04-21-2016, 03:28 AM
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Quote:
Originally Posted by ravenworks View Post
A good in theroy idea,but if they want your Jeep it will be gone in 30 seconds or less.
Most car thief's are professionals.
I'm not worried about the professional, they usually don't go 50 miles from nowhere on the chance they might find a Jeep at a trailhead. Most are local kids looking for a thrill.
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post #6 of 20 Old 04-21-2016, 03:29 AM
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Quote:
Originally Posted by Grecy View Post
I looked into the wiring diagrams, and the way the computer senses which gear the auto is in is a complicated beast. I would not want to mess with it.

If I had an auto, I'd look at putting a switch in some other relay. Maybe the fuel pump, or maybe the ASD relay (auto shut down).

-Dan
Yeah, I was thinking the pump as well, easier to get at.

Where did you get a WD? I've been looking for a service manual for the 2016 JK, closest I've found (at reasonable price) is a 2008.
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post #7 of 20 Old 04-21-2016, 05:09 AM Thread Starter
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Quote:
Originally Posted by ravenworks View Post
A good in theroy idea,but if they want your Jeep it will be gone in 30 seconds or less.
Most car thief's are professionals.
I'm driving around Africa for two years, I'm not expecting to encounter too many professional car thieves that are familiar with Jeeps.

The reason I did this is so that if someone gets the keys off me by force, they still can't start it.

-Dan

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post #8 of 20 Old 04-21-2016, 05:12 AM Thread Starter
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Quote:
Originally Posted by tecumsa View Post
Yeah, I was thinking the pump as well, easier to get at.

Where did you get a WD? I've been looking for a service manual for the 2016 JK, closest I've found (at reasonable price) is a 2008.
I have the service manual for a 2007. I didn't look for a newer one, though I would think if you can find a 2012+ you'll be fine.

The ASD (auto shut down) relay would be an interesting one to use. It's what the computer uses if it wants to shut the engine down, like when you use a non-chipped key. The engine starts, then turns off within 2 seconds. You could figure out a way to make it do that, unless you are holding down a button somewhere.

-Dan

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post #9 of 20 Old 04-21-2016, 05:45 AM
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On my 89 I got a Bosch 30A relay and put it beside the other relays under the hood on the firewall, it matched them. I cut the line going to the starter, not the battery line but the line that trips the starter relay and spliced each end into the switched leads of the new relay. I ran a control wire inside the cabin for the relay and grounded the relay at the firewall. I drilled out the connection for the cigarette lighter and got a push button switch from Radio Shack and put it in the lighter housing. I used the +12v power from the lighter and connected the control wire to the one pole of the switch and the power to the center. The switch was the right length that I put the lighter back in and if I wanted to disable the Jeep I simply pushed the lighter once. That switched my relay and interrupted the starter signal from the key. All wiring was loomed and taped to match the factory wiring so you would really have to look to tell what was done. I'm not sure if that would work on the new Jeeps, I'll find out soon but it is another option.
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post #10 of 20 Old 04-21-2016, 05:49 AM Thread Starter
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Quote:
Originally Posted by Snowdogs View Post
On my 89 I got a Bosch 30A relay and put it beside the other relays under the hood on the firewall, it matched them. I cut the line going to the starter, not the battery line but the line that trips the starter relay and spliced each end into the switched leads of the new relay. I ran a control wire inside the cabin for the relay and grounded the relay at the firewall. I drilled out the connection for the cigarette lighter and got a push button switch from Radio Shack and put it in the lighter housing. I used the +12v power from the lighter and connected the control wire to the one pole of the switch and the power to the center. The switch was the right length that I put the lighter back in and if I wanted to disable the Jeep I simply pushed the lighter once. That switched my relay and interrupted the starter signal from the key. All wiring was loomed and taped to match the factory wiring so you would really have to look to tell what was done. I'm not sure if that would work on the new Jeeps, I'll find out soon but it is another option.
Nice! I see no reason at all that won't work. The little wire going to the starter is always the same, if you can interrupt it, you can stop the car from starting!

-Dan

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post #11 of 20 Old 04-21-2016, 06:06 AM
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Quote:
Originally Posted by Grecy View Post
I'm driving around Africa for two years, I'm not expecting to encounter too many professional car thieves that are familiar with Jeeps.

The reason I did this is so that if someone gets the keys off me by force, they still can't start it.

-Dan
Ditto, though most trail people who have vehicles stolen have it done while they're on the trail. Not too many people have parking lot encounters, first they'd have to deal with my 2nd Ammendment rights. Biggest concern is coming back to find the Jeep gone, kids know they have hours before a loss is noticed, and even more time before it can be reported.
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post #12 of 20 Old 04-21-2016, 06:14 AM
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Nice! I see no reason at all that won't work. The little wire going to the starter is always the same, if you can interrupt it, you can stop the car from starting!

-Dan
I like the starter idea, simple. On my TJ (sigh, to be sold) I broke the connection to the ignition in the column, easy to do on a TJ. The switch is a micro that I mounted under the ash tray. I remove the ash tray, press the switch, you can't start it.
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post #13 of 20 Old 06-07-2017, 11:09 AM
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Does anyone know the difference between the PCM plug layout in the OP vs the one shown in my pic? I was able to locate the yellow wire with orange stripe in the plug closest to the engine, but I'm hesitant to cut it without some sort of assurance that the wire color coding in this version of the plug layout is the same as in the OP.

Thanks!
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post #14 of 20 Old 06-07-2017, 09:33 PM
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By the way, figured out the answer to my own question using a diagram found here: http://www.bbbindustries.com/free_tsb.html

Short answer, yes, it is still the yellow/orange wire on the innermost plug.
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post #15 of 20 Old 06-08-2017, 02:34 PM
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Here is a simple idea, but it works.
When I used to go hiking/camping while in college, I'd simply pop the hood of my S-10, and remove a couple of the spark plug wires and take them with me. They would not get very far running on 4 out of 6 cylinders.

Back to the original idea...This is an awesome thread! Thanks for sharing.

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