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  #1  
Old 01-28-2019
jdub79 jdub79 is offline
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Default Push Button Start Help!
I've looked everywhere for a solution to the problem I'm having. All I want to do is have a push button that cranks and starts my 2014 Wrangler when the key is in the 'ON' position. So, I'm not looking to go keyless. I have a relay setup that runs to the momentary switch, and it needs three connections - ignition power (pink/white @ ignition switch harness), ground (black from ignition switch harness), and starter. I've tried the violet/brown at the ignition switch harness, but it does not work.
None of the wires that I can find under the steering column test 12V when the engine is cranking. I ran a temporary wire for my starter wire to the large yellow/grey wire at the blue connector under the TIPM. That at least produced cranking when I turned the key on and pressed my momentary switch. However, the Jeep would not start. Is there something I'm missing? My mind tells me that all the anti-theft should be a non-issue with the key in the 'ON' position, so why wouldn't the yellow/grey starter wire work?
I figured I'd post and hope someone has more wiring experience than me. Here's hoping someone can help!

Thanks a million!
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Old 01-28-2019
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theksmith theksmith is offline
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Default Re: Push Button Start Help!
whether your Jeep has the SKIM (chip key) or not shouldn't matter since you're planning to have the key in the ignition and in the ON/RUN position... however, who knows what all the PCM actually does when it's told to start the rig - i.e. it's probably a lot more than just pulsing the starter (like setting throttle position based on temperature, etc.).

with that in mind, i think the right thing would be to simulate the key actuallying turning to START, which you should be able to do with a momentary DPDT switch and the wires going to the ignition cylinder...


here's the pinout for the Ignition Switch C1 connector on your 2014 JK:




when the momentary DPDT switch is pressed, you'd want:

- 1) one set of contacts to connect the SENSE/MUX wire to ground through a 180 Ohm resistor.

- 2) one set of contact to connect the RUN/START wire to +12v.


the only thing i'm not sure on is whether you need to also temporarily disconnect the MUX wire from the ignition cylinder while you ground it through the resistor, or if you can just leave it connected...

you could of course use a regular momentary SPST switch to trigger a DPDT relay instead of using a DPDT switch. in fact this might be the better way to go since you could have the 2 sets of Normally-Closed contacts connect the SENSE and RUN/START wires to the ignition cylinder and then when the relay is activated those connections would break and the Normally-Open contacts would make the 2 new connections i mentioned above.

also, you might consider hacking up a cheap T-Harness like the THCHD2 instead of splicing into the factory wiring.
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Old 01-28-2019
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theksmith theksmith is offline
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Default Re: Push Button Start Help!
thinking about it a little more...

if you wanted to use just the DPDT switch (i.e. you are making connections in parallel with the existing connections instead of breaking those with the NC/NO contacts of a relay), you should be able to ground the SENSE/MUX wire through about 256 Ohm instead of 180.

the reason would be that when the ignition cylinder is in the ON/RUN position, it's already grounding the SENSE wire through 610 Ohms... so if you don't break that connection, then putting 256 Ohm in parallel gives you the 180 Ohm value that the PCM expects for the START position.
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Old 01-28-2019
jdub79 jdub79 is offline
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Default Re: Push Button Start Help!
So, you're saying I'd have to turn the key to 'ON', then flip a switch, then push my normally-open momentary switch?
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Old 01-28-2019
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theksmith theksmith is offline
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Default Re: Push Button Start Help!
Originally Posted by jdub79 View Post
So, you're saying I'd have to turn the key to 'ON', then flip a switch, then push my normally-open momentary switch?
no, you just need a momentary switch with 2 sets of contacts (DPDT) - so that pushing it can complete 2 different circuits at the same time. ...or you can use your existing momentary switch to trigger a relay that has 2 sets of contacts.
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Old 01-29-2019
jdub79 jdub79 is offline
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Default Re: Push Button Start Help!
Originally Posted by theksmith View Post
no, you just need a momentary switch with 2 sets of contacts (DPDT) - so that pushing it can complete 2 different circuits at the same time. ...or you can use your existing momentary switch to trigger a relay that has 2 sets of contacts.
Of course, there's a disclaimer on this....this may not work, or are you pretty sure? Any chance I could royally f* something up here? Could you possibly explain exactly how to connect all of this? I'm stubborn, and the challenge keeps drawing me in, even if if may be a silly thing in some eyes...
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Old 01-28-2019
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Curly Curly is offline
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Default Re: Push Button Start Help!
Originally Posted by jdub79 View Post
I've looked ................ (snip).....I'm missing? My mind tells me that all the anti-theft should be a non-issue with the key in the 'ON' position, so why wouldn't the yellow/grey starter wire work?
I figured I'd post and hope someone has more wiring experience than me. Here's hoping someone can help!

Thanks a million!

The modern vehicle with multiplexing, lan networks, etc is fairly complicated. The pcm and body computer will both be involved in starting. Anti- theft is definitely in play. Simply hot wiring the starter will crank the engine but may or may not start the engine depending on year/make/model of the vehicle.
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Old 01-29-2019
jdub79 jdub79 is offline
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Default Re: Push Button Start Help!
Is there a JK-specific bypass module that could be used, that would bypass/disable the anti-theft by turning on when the key is turned, then the button would work while connected to the TIPM yellow/grey wire?
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Old 01-29-2019
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theksmith theksmith is offline
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Default Re: Push Button Start Help!
IMO, anything posted on a forum, blog, or social media site should be considered "proceed at your own risk"!

not trying to be an ass, but it doesn't sound like you have a ton of electronics experience - so yes, you could easily fry your PCM, BCM, SKIM module, or something else with even a split second touch of the wrong wires together.
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Old 01-29-2019
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Default Re: Push Button Start Help!
So out of curiosity, I looked at the wiring diagrams. Using a push button to power the starter through the yellow/gray wire is bypassing 2 different parts of the Can system. Turing the key to start sends a voltage signal through the pink/white wire to the Sentry Key module (Skim) and to the TIPM. At the TIPM, there is a symbol for the Can bus circuit, whose signal is probably being used to power the coils, injector and fuel pump. So, although the engine is turning, the signals from the CKP and CMP are being ignored since the PCM doesn't see a start signal.
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