Where to wire a kill switch in a Ford Ranger?
If you’re like me and work away for a living, or are security conscious of your new ute, then you might want to install a kill switch in your car.
In this post I will go through my experiences and tests on where to wire a kill switch in a Ford Ranger or Mazda BT-50 (they were the same car up until late 2020 when Mazda paired with Isuzu).
There is a lot of information floating around Youtube and the forums, but it is often quite generic and not specific to Ford Rangers, Mazda BT-50s or diesel engines.
I also have a post about where to pick up an ignition feed in a Mazda BT-50 or Ford Ranger, or where to find a dash light feed as well.
Why would you want to wire a kill switch?
A kill switch will prevent the engine from starting even if someone has somehow got the key to your vehicle. For example, you’re at the beach and somebody goes through your bags, they go to your car, get in, go to start it and nothing happens.
It is not a foolproof system, as a determined thief might know to look for such a thing, or be dedicated enough to re-wire the car to work, but that is quite unlikely for the most common opportunistic types of theft.
About this post
Before we get started, some quick information about how and why I went about things the way that I did, and some other disclaimers.
To skip forward and find out where to wire a kill switch in a Ford Ranger or Mazda BT-50, please use the table of contents at the top of the page.
What this post covers?
This post will cover which cables to cut into for a kill switch on a Ford Ranger and Mazda BT-50 circa 2015, but the concepts can be transposed across other models and manufacturers.
This post will not cover where to physically install the kill switch.
The actual location of the kill switch should be secret, everyone has different ideas about placement and it’s not wise to share them, otherwise the purpose of the switch is defeated.
Abbreviations
To save time here are some abbreviations that will be used in this post and what they mean;
- BCM – Body control module is located behind the driver’s storage compartment, above the pedals. It houses an assortment of fuses and plugs that go in all directions through front and rear wiring harnesses.
- TCM – Transmission control module. This is located to the right of the accelerator pedal and is extremely difficult to remove the plug and pins from (I broke the plastic cover in attempting to remove it).
- TSS – Transmission selector switch (automatics). This is simply the lever that you use to select gears.
Methodology
To figure out what I needed to know involved a lot of frustration in trying to remove trim without damaging the trim, or any existing cables.
I disconnected the negative terminal at the battery to prevent any accidental airbag deployment when removing trim.
Essentially, after acquiring two separate wiring diagrams the process went a little something like this;
- Watch Youtube video from ChrisFix about wiring a kill switch into the fuel pump.
- Realise to my dismay that the fuel pump (if drawings are correct) does not stop diesel engine from starting and could possibly cause damage.
- Find cables for ignition in BCM, and power feeds for TCM and test by pulling fuses if cables will work.
- Live testing by reinstating fuses, pulling cables out from the back of their plugs (very frustrating process) and attempting to start car.
- Pulling wires out of the TSS one at a time to see what effect they have if any on starting the car.
- Making the final decision and testing it with the switch.
TL;DR – Pulled fuses, pulled cables, tested different options live and chose my favourite.
Limitations
I am not an auto electrician.
I was curious about a few things, and had some drawings at my disposal (thanks to hours of searching the internet and also buying a workshop manual).
However the inner workings of the PCBs (printed circuit boards) made it hard to know exactly how to achieve what I intended in my mind.
My original desire was to cut into the neutral selector switch to trick the car to thinking it was in ‘Drive’ and refusing to start, but in the end I couldn’t quite do this as the actual neutral safety switch is built into the 6R80 automatic transmission and was inaccessible from the cabin.
This post is not an exhaustive list of all the possible options, it only represents a fraction of the options with the idea being that the circuit that is cut into is accessible in the cabin, so your switch and its intercepted cable are easy-ish to access and work on.
I tried to avoid entering the engine bay and touching any of the relays.
This way if you decide to mount the switch within arms reach of the driver’s seat, you will have minimal cabling to run to get to the switch and back.
*Affiliates Disclosure
Affiliate links are present on this page. Through partnerships with, but not limited to: Amazon, eBay and Commission Factory, I will make a small commission through qualifying purchases. This comes at no extra cost to you and is just a way for me to try and support myself and the blog. Thank you.
Before you start wiring a kill switch in a Ford Ranger
Let’s move onto the pre-job briefing, first things first you’ll need some gear.
Gear needed to wire a kill switch in a Ford Ranger
This is pretty simple, you only need a handful of things (note these are affiliate links but these are the exact things I ordered myself);
- 12v toggle switch.
- Cable.
- Lugs / Crimps.
- Conduit.
- Cable Ties.
- Electrical Tape.
- Crimpers / Strippers.
- Trim removal set.
You may notice that there is no heat shrink or solder mentioned, that’s simply because I didn’t use it. I think crimping gives a great result and is less prone to cracking due to poor quality solders.
Crimping with the male/female lugs mentioned also allows for the quick disconnection of the switch if it is faulty and requires a change out.
On top of that, if the wire you cut into has 1x male and 1x female connector on it, then if you ever want to bypass the switch you can simply put the original wire back into service within minutes by connecting the two ends again.
It is up to you if you want to heat shrink, but tape is easier to remove in the future, looks more like the original factory wiring harness, and waterproofing shouldn’t be an issue here.
Outside of the things listed you will need some basic hand tools for screw removal, battery disconnection, and cutting of cables.
How long does it take to wire a kill switch?
It will take about 2 hours if you haven’t done this before, less if you’re experienced.
For me this whole process took about 6 or 7 non-consecutive hours, but that involved a lot of back and forth, as well as removing and reinstating the body trim about 3 times, removing fuses, pulling plugs apart and so on.
12 Volt basics
To summarise.
- Make sure all cable sizes you select are adequate to carry the amount of power required for that circuit, the current carrying capacity must be higher than the amperage of the fuse.
- Make sure the switch is rated to carry the current as well. This shouldn’t be an issue for the examples shown in this post, but if you choose to interrupt a different system this could be relevant.
- It is good practice to disconnect your negative from the battery while working around removing trim in case the airbags go off by accident and you’re nearby with tools in your hands.
- It is also best to make all of your joins in the cable with a dead wiring system. Although the cables being cut into should be ignition switched they may not be, or the wrong cable could be cut and it could short on a metallic surface.
Where to wire a kill switch in a Ford Ranger / Mazda BT-50?
Alright, time to go through all the best places I found, as well as cover the options I tried but found to be a failure. To start with I will give you 2 locations I think are best and work my way backwards from there.
The drawings I used
Below is the drawing that we will reference for plug connection names and numbers. I worked off this document as well as a purchased Haynes online and paperback workshop manual (affiliate link).
Both manuals displayed the exact same information, with different naming used for the plugs.
All listed cable colouring as well as suggested cable paths were identical, and I constantly went back and forth to both sets of drawings to ensure I was about to disconnect the correct cable.
For those who are wondering, this is the body control module, it is located behind the driver’s storage compartment where the fuses are.
See below.
Option 1 – Wire a kill switch to the ignition swith
If you look at the above drawing of the BCM (or check your owner’s manual), you will see that fuse 78 is labelled ‘ignition switch’.
You can confirm this will work by removing said fuse and attempting to start the car (this should be done before disconnecting the negative obviously).
And if the following drawings are correct, the cable that needs intercepting is at plug J08-3.
*Note that “F3” in the Haynes manual is J08-3 in the drawing we are using for plug naming and numbering.
What colour is this wire?
The wire that is connected to J08-3 is brown / red.
What does using this wire do?
Using this wire will stop the car from completing the ignition circuit.
Benefits of using this wire?
This wire is protected with a 5A fuse. It is a small fuse which means you can get away with using smaller cables in comparison to intersecting the fuel pump or the power supply to the BCM.
Disadvantages of using this wire?
This cable is easy to find if someone was really dedicated to taking your car.
Option 2 – Wire a kill switch to the ignition relay coil
If you check your owner’s manual you will see that fuse 50 is labelled ‘ignition relay, relay coils’.
You can confirm this will work by removing said fuse and attempting to start the car (this should be done before disconnecting the negative obviously).
And if the following drawings are correct, the cable that needs intercepting is at plug J06-14.
*Note that “D14” in the Haynes manual is J06-14 in the drawing we are using for plug naming and numbering.
What colour is this wire?
The wire that is connected to J06-14 is brown / grey.
What does using this wire do?
Basicall the same as the above but in a different way, it will stop the ignition relay coil from activating and completing the circuit.
Benefits of using this wire?
This wire is also protected with a 5A fuse. It is a small fuse which means you can get away with using smaller cables.
Disadvantages of using this wire?
This cable is easy to find if someone was really dedicated to taking your car.
Option 3 – Wire a kill switch to the TCM feed
Initially I wanted to use the cable that told the car that it was in park/neutral and allowed it to start. This lead me to looking at the TCM and the TSS.
Unfortunately I couldn’t find it (apparently it is within the gearbox itself), so I tried other options related to the gearing of the car.
The TCM has 2 fuses you can pull to stop the engine from starting: fuse 27 and fuse 33.
Although pulling either of these fuses will stop the car starting, the only cable you can cut into here is the cable leading to TCM-33, from fuse 33.
Fuse 27 has parallel feeds (as is shown below) to TCM-1 and TCM-31, so when I disconnected those cables individually, the car still started.
What colour is this wire?
The wire that is connected to TCM-33 is white / brown.
What does using this wire do?
It stops the TCM from receiving power, and the car will not start without a healthy signal from the TCM.
Benefits of using this wire?
This wire is hard to access and not many people will know to look for it.
Disadvantages of using this wire?
This plug is very difficult to take apart and you risk breaking plastic clips. However for those who are not trying to remove cables for testing purposes and only want to access the wiring harness, this may not be as big an issue.
Where is the TCM?
Near the accelerator pedal, see images below.
Option 4 – Wire a kill switch to the TSS
I went through the TSS and disconnected the cables one by one. There was one result that was a semi success, although it didn’t appear on the cable that I thought it would.
As you can see in the images above, there is a second cable circled in red that is not to do with the TCM but rather the TSS.
When I removed this cable, the car was able to start but it would not move out of ‘park’.
This wire can be intercepted at the BCM at plug J02-43 or at the selector switch, number 3.
What colour is this wire?
The wire is blue / orange on Fords and violet / green on Mazdas.
What does using this wire do?
The car will start but the interlock for selecting gear will not work, it is as if the car does not recognise that a key is in place to change gear.
Benefits of using this wire?
It is a confusing thing for someone to experience as there is no other evidence of tampering, any attempt at stealing the car might be discarded in frustration.
Disadvantages of using this wire?
Although I forgot to test whether it works, I am assuming that someone who knows how to override the gear selector in an automatic could simply use the override and drive away.
Option 5 – Wire a kill switch to the fuel pump
This method is the one you see mostly on Youtube, but I don’t find it very useful at all.
If you check your owner’s manual or the image of the BCM at the top of the page you will see that fuse 56 is labelled ‘fuel pump’.
And if the following drawings are correct, the cable that needs intercepting is at plug J07-9.
Initially I wanted to stop the relay from activating rather than intercepting the outgoing power, but the relay appears to be a part of the printed circuit board inside the BCM and can’t be tampered with.
*Note that “E9” in the Haynes manual is J07-9 in the drawing we are using for plug naming and numbering.
What colour is this wire?
The wire that is connected to J07-9 is yellow / grey.
What does using this wire do?
I assume it stops the fuel pump, but I can’t prove this as the car still started and I didn’t want to run it for long and risk damaging it and needing to prime the fuel manually.
I don’t know enough about diesel engines to recommend this method being safe or unsafe for the engine.
Benefits of using this wire?
I don’t see many benefits.
Disadvantages of using this wire?
20A fuse protection means a higher rated switch is needed (>20A) as well as larger cables required.
The car also still starts and may not switch off for several kilometres, defeating the purpose of it entirely.
Conclusion
That’s it for this post, hopefully it saves you hours of searching for good methods on forums or Youtube. You now know where to wire a kill switch in a Ford Ranger as well as a Mazda BT-50.
Whatever car you drive will have similar circuitry, but you will need to find vehicle specific drawings for your application.
There are of course other methods, like always there are plenty of ways to skin a cat.
For those who are more creative you can wire in circuits that activate horns etc.
Although they sound fun, the likelihood of your car being stolen is low and putting in these deterrents is a good-enough-for-most-situations fix.
There’s no reason to go overboard with complex circuits.
