Hidden Kill Switch

[Snoranger]

1999 Ford Ranger with 4.0l(V6) will have PATS(passive anti-theft system) which turns off fuel pump and fuel injectors unless one of its Factory transponder keys is used in the ignition

Fuse 19 in the cab fuse panel, 25amp, powers the coil pack and the computer relay, so if its disconnected then No Start


I wouldn't disable starter motor because I like the idea of engine cranking, making noise, but not starting, this calls attention to the THEFT attempt
People might ignore an alarm now-a-days, lol, but may offer to help someone with a No Start after repeated cranking, something a thief wouldn't want


Best setup is a Double relay, with a button
This is a momentary contact setup, so system is disabled until button is pressed once, then first relay is activated which activates 2nd relay which stays on until key/power is off again
So it resets every time you turn off the key, no remembering to "turn off the switch"
And it shouldn't reset while driving, for Dirtman

If you wire it into a key on circuit, you only need a single relay and a momentary push button to make it latching.
Pin 30 - key on input and feed to push button.
Pin 87 - out to load and input to 86
Pin 86 - in from 87 and input from push button.
pin 85 - ground.

That would turn it on with the push button and keep it on with its own output. That would latch it on until the key gets turned off.

 

[pjtoledo]

How about wiring it to the airbag? The thief is reaching down around the column trying to hot wire it.... BAM! Airbag to the face.

better idea, the seat belt tensioner, which is under the drivers seat

 

[Curious Hound]

better idea, the seat belt tensioner, which is under the drivers seat

You’re depending on a thief using the seatbelts. No guarantee there

 

[Dirtman]

What thief is putting on his seatbelt before stealing your truck. Be a nice little bang... but nothing else lol.

 

[PaulZ]

Thanks all, got it covered!

 

[Dirtman]

I still endorse trunk monkey as the only true anti theft system

 

[PaulZ]

Hey regarding the special key for the alarm thing, here is the key I have been using, is there something special about it? I do have an alarm light on the dash that blinks, and I have another key with a fob that turns it on but I never use it.

 

[91stranger]

If the key has a letter then it probably has a chip in it. When I had my spare key made they said it wouldn't start the engine since it had the letter on the key.... It still started the truck so who knows if that's true or not.

 

[Dirtman]

Yes it is a transponder key. It has a tiny chip in it. When you put it in the ignition there is an antenna that sends out a tiny burst of energy and receives a coded signal from the key. The computer must get this code to allow the truck to start.

 

[Dirtman]

If the key has a letter then it probably has a chip in it. When I had my spare key made they said it wouldn't start the engine since it had the letter on the key.... It still started the truck so who knows if that's true or not.

Up until 2001 I think only the 4.0 trucks had the PATs system. I could be wrong but I know for a few years they didn't put it in the "cheap" trucks. After 2001 all model rangers had it (except in 2005 for some reason when nothing had it).

The system "in theory" is not hard to defeat with a laptop, an elm327 adapter, and a couple of blank keys. But I dont think any thief is gonna sit their with a computer trying to hack into a 20 year old truck... I know what I'm doing and could probably only pull it off if you give me 15-20 minutes and I'd need to know the truck beforehand. Not worth the risk for a truck worth a couple grand.

 

[PaulZ]

So the chip is in the black plastic part? 'Cause I was gong to break that all off to save some room in my pocket.

 

[Curious Hound]

So the chip is in the black plastic part? 'Cause I was gong to break that all off to save some room in my pocket.

Bad idea

 

[sgtsandman]

If it's a PALS key, yes the chip is in the black plastic part. Cutting or breaking that part of the key will disable or destroy the chip and won't allow your truck to start.

 

[Dirtman]

The chip itself tiny. I had pure metal keys with chips (gm not ford) I think gm calls it pass lock but same thing. Definitely do not mangle the key unless you are 100% positive you do not have PATs. I feel bad for you if you think that key is too big lmao. Dont buy a new car! The keys to my 2017 are massive.

 

[Snoranger]

If you look at the top of the key, you can see a small outline of where the chip slides in the plastic part of the key.