HELP!!!!!!!!!! 2012 jku won't start!
JK Super Freak
Joined: Feb 2009
Posts: 1,488
Likes: 1
From: Sydney, Australia
Great to hear the old disconnect-the-battery-trick worked! I guess we sometimes forget that modern vehicles are more like computers than transportation devices & occasionally the operating system becomes corrupted & needs a complete shutdown and reboot, just like a PC or a cellphone.
One side effect you may experience is that since disconnecting the battery for over 15 minutes resets everything (including the tune) back to the way it left the production line, the PCM will need a few hundred miles to "re-learn" while the motor reaches its various targets on the look-up tables for the fuel maps in the EFI system, & the transmission's controller (if it's an auto) will also take time to re-learn your driving style and adjust shift patterns. It's the reason why you need to do the "re-boot" every time you add a new exhaust, throttle body, supercharger, etc as the computer needs to adapt to a different set of parameters.
During this time the Jeep may have a different driving "feel" to it, but after a short time it will re-learn everything and go back to the way you're used to it.
One side effect you may experience is that since disconnecting the battery for over 15 minutes resets everything (including the tune) back to the way it left the production line, the PCM will need a few hundred miles to "re-learn" while the motor reaches its various targets on the look-up tables for the fuel maps in the EFI system, & the transmission's controller (if it's an auto) will also take time to re-learn your driving style and adjust shift patterns. It's the reason why you need to do the "re-boot" every time you add a new exhaust, throttle body, supercharger, etc as the computer needs to adapt to a different set of parameters.
During this time the Jeep may have a different driving "feel" to it, but after a short time it will re-learn everything and go back to the way you're used to it.
JK Newbie
Joined: Jul 2011
Posts: 24
Likes: 0
From: Central Kentucky
Did he state that disconnecting the battery helped?
On my KJ, when the anti-theft system shut down access to start the Jeep, the battery had NOTHING to do with it. Any thief could disconnect a battery. The thing I had to do to be able to start the Jeep again was a procedure I found in the owners' manual. I am not sure which of these suggestions was the one that got him rolling again.
On my KJ, when the anti-theft system shut down access to start the Jeep, the battery had NOTHING to do with it. Any thief could disconnect a battery. The thing I had to do to be able to start the Jeep again was a procedure I found in the owners' manual. I am not sure which of these suggestions was the one that got him rolling again.
JK Super Freak
Joined: Feb 2009
Posts: 1,488
Likes: 1
From: Sydney, Australia
Yep, I believe he did:
...The imobilizer light is on so it all points to this. Battery is currently disconnected and waiting for 30 min. I pray this works...
...BIG thanks guys! lights off and shes running. Love this forum...
Thread Starter
JK Enthusiast
Joined: Aug 2011
Posts: 109
Likes: 0
From: Turlock, Ca
Great to hear the old disconnect-the-battery-trick worked! I guess we sometimes forget that modern vehicles are more like computers than transportation devices & occasionally the operating system becomes corrupted & needs a complete shutdown and reboot, just like a PC or a cellphone.
One side effect you may experience is that since disconnecting the battery for over 15 minutes resets everything (including the tune) back to the way it left the production line, the PCM will need a few hundred miles to "re-learn" while the motor reaches its various targets on the look-up tables for the fuel maps in the EFI system, & the transmission's controller (if it's an auto) will also take time to re-learn your driving style and adjust shift patterns. It's the reason why you need to do the "re-boot" every time you add a new exhaust, throttle body, supercharger, etc as the computer needs to adapt to a different set of parameters.
During this time the Jeep may have a different driving "feel" to it, but after a short time it will re-learn everything and go back to the way you're used to it.
One side effect you may experience is that since disconnecting the battery for over 15 minutes resets everything (including the tune) back to the way it left the production line, the PCM will need a few hundred miles to "re-learn" while the motor reaches its various targets on the look-up tables for the fuel maps in the EFI system, & the transmission's controller (if it's an auto) will also take time to re-learn your driving style and adjust shift patterns. It's the reason why you need to do the "re-boot" every time you add a new exhaust, throttle body, supercharger, etc as the computer needs to adapt to a different set of parameters.
During this time the Jeep may have a different driving "feel" to it, but after a short time it will re-learn everything and go back to the way you're used to it.
JK Enthusiast
Joined: Jun 2011
Posts: 114
Likes: 0
From: NM
Interesting you say this. Jeep feels much more peppier and also my mileage according to the dash went from 15.3 mpg to over 18.. Weird. Shifting actually improved a bit (was shifting funny due to adding bigger tires and not programming yet). We'll see how long this lasts but I like it....
You just stumbled on the next mod trend.
JK Newbie
Joined: Nov 2016
Posts: 1
Likes: 0
From: Edmonton
Silly key FOB
Thanks to everyone who chimed in. I ran into the same problem with my 2012 jku rubi. Drove home from work, parked it and the next day...nothing. All of the lights worked, dash lit up and stereo worked fine. I got a red lightening bolt and a check engine symbol remain on after I turned the key to where the starter should engage.
What it turned out to be was the key fob. I tried my spare key and she fired right up. after that, my regular key worked again too. Me thinks the computer disallowed my key and saved that info in the system but reset the allowance once she was started with an allowed key. Kinda sounds like something a stupid computer would do
If that is the case, disconnecting the negative battery terminal for 30 min would/should have the same desired affect.
Be well and kepp the shiny side up
What it turned out to be was the key fob. I tried my spare key and she fired right up. after that, my regular key worked again too. Me thinks the computer disallowed my key and saved that info in the system but reset the allowance once she was started with an allowed key. Kinda sounds like something a stupid computer would do
If that is the case, disconnecting the negative battery terminal for 30 min would/should have the same desired affect. Be well and kepp the shiny side up