HOW-TO: DIY Kill Switch for JK Wrangler

[Dan Grec]

A hidden kill switch is great theft deterrence - even if someone manages to get your keys, they still won’t be able to start the Jeep. It’s an easy DIY on the cheap, total time is something like 30 - 45 minutes.

Things to buy

• A small momentary switch like this: Momentary car push button switch for about $8.
• Some wire like this: 12ga 25' Red/Black hookup wire for about $7

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:

We’re 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 I’m used to vehicles that don’t 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 shouldn’t 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 don’t think it’s 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 don’t have plastic “spaghetti tubing” 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 don’t rub on the edges of the hole in the firewall.



Step 4:

Find a place to mount your hidden switch. Obviously I’m 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 you’ll 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 “felt”. 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 pressed…. 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 it’s there…
• 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 it’s running you can let go.

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

-Dan

 

[unkamonkey]

Why not just put a hidden toggle switch on the wire going to the fuel pump? The KISS method.

 

[Dan Grec]

Why not just put a hidden toggle switch on the wire going to the fuel pump? The KISS method.

There are many ways to skin this cat obviously.

I wanted to stay away from the fuel pump wire for a few reasons:

1. That's a 10amp wire, so your switch and wire needs to be able to handle that current.

2. You have to manually turn it on to start and run the Jeep, then remember to manually turn it off again when you stop driving.
If you forget to turn it off, or just can't be bothered for the 5th time today, you don't have the protection from theft.

3. The wiring for the fuel pump is over on the passenger side, and I didn't want to have to run it all the way across and back again.

4. If someone did run the Jeep with the fuel pump turned off, it would likely run for a little while before running itself dry - who knows how far they'd get, if they'd wind up stuck in traffic, and if that will damage the engine at all.

And for me, the big one

5. I don't have an electronic fuel pump in my JK

-Dan

 

[TenaciousTJ]

Think I'm gonna do this. Two 2014 hardtop JKs were stolen in my city last night.


Sent from my iPad using Tapatalk

 

[Kiddmen57]

would this work on an auto trans?

 

[wADVr]

Re auto trans. Yes I think something like this could be done just with the neutral safety switch instead of the clutch switch. Would have to read up on how these signal the computer of being in park or neutral. The old ones I believe closed a loop, but can't remember exactly.

 

[Dan Grec]

Re auto trans. Yes I think something like this could be done just with the neutral safety switch instead of the clutch switch. Would have to read up on how these signal the computer of being in park or neutral. The old ones I believe closed a loop, but can't remember exactly.

I looked at the factory service manual because I wanted to include this in the HOW-TO.

Unfortunately, the NSS in the JK is a very complicated beast. It's integrated into the trans and uses a variable resistance to tell the PCM what gear the trans is in.
Without having one to play with, I don't fell confident writing it up.

If I had an auto, I'd probably just put a switch on some other wire.

-Dan

 

[wADVr]

That figures.

Good job on your write up, I like the use of the momentary switch for the reasons you explained.

 

[Dan Grec]

Wow, cars are not what they used to be...

Anyway, I dunno on newer Jeep, but some automatic cars, the harness around the pedals is the same as the manual trans version. The wiring connector for the non existant clutchpedal interlock has a jumper plugged in.
Thats a handy place to intercept.

The factory JK service manual is very vague about the differences between an auto and a standard JK.

I'd need to see an auto, and I'd need to inspect the connectors on the PCM to see exactly what they have plugged into that same cavity. It's possible it's just grounded, and could be used as you suggest.

-Dan

 

[HAFICON]

I would love this on my auto JK. Maybe someday...