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Discussion Starter #1
Hey Jeep owners, so I’m completely stumped! Literally one day out of the clear blue sky, my Jeep stopped starting. Nothing outta the ordinary happened, just one morning it wouldn’t start. The ignition switch is not getting any power.

I checked everything possible, even replaced some fuses just in case, and still nothing! I gave the it12 volts directly you the wire, and it started right up without a hitch. But otherwise, the switch is getting no power.

No clue why it stopped getting power all of a sudden. Literally nothing happened, it just stopped! Anyone have ANY clues as to what it might be??

Battery is good, fuses are good, wire and wire harness connections are all goochie...
 

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The ignition switch receives power from fuse M27. Should be a 10A fuse. You say the fuse is good but have you tested it with it in place? It's a mini fuse and should have little metal contacts exposed on the top of fuse that allow you to test it. Grab a test light, clamp it to battery negative. Then touch each side of the fuse leg...though those exposed holes on the top. Does the test light light on each side? If it does, then you have an issue from the right side of the fuse to the ignition switch. Could be wire, could even be part of the TIPM. If it lights on one side but not the other it's a bad fuse. If it doesn't light at all then something is not right in the TIPM (assuming the TIPM is getting power).
 

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Play with the shift lever a little and see if that works. Shift to neutral and back to park several times
This. Put it in neutral and see if it starts... if it is, neutral safety starter switch is your issue. The switch isnt recognizing the gear is in park so not allowing it to kick over.

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This. Put it in neutral and see if it starts... if it is, neutral safety starter switch is your issue. The switch isnt recognizing the gear is in park so not allowing it to kick over.

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The Neutral safety switch is not in the circuit the OP is describing therefore messing with the shifter won't change anything. If he provides power to the ignition switch the Jeep starts when the key is turned to start. The neutral safety switch is on a different circuit tied to the PCM.
 

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Can bus systems sense key position via resistance at key switch
The resistance is sensed but the WIN which then sends out a can bus signal

It is not a power connection switch


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Can bus systems sense key position via resistance at key switch
The resistance is sensed but the WIN which then sends out a can bus signal

It is not a power connection switch


Sent from my iPhone using Tapatalk
A few things are at play with the JK ignition switch. The ignition switch does require battery postive that is provided by the TIPM. When you switch to run or start, 12v gets sent to the WCM (wireless control module) and to the TIPM. There is another wire that comes from the ignition switch into WCM. This wire actually will contain different voltages depending on what position the key is in. The service manual has a table of these. From here the WCM translates that to the key position and sends a message on the CAN bus. The TIPM then looks for that message to be in start and the 12v on the first wire. Then it will tell the PCM to do a start. The PCM then looks for all the conditions to start, including neutral safety switch and initiates a start.
 

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Discussion Starter #8
Play with the shift lever a little and see if that works. Shift to neutral and back to park several times
This. Put it in neutral and see if it starts... if it is, neutral safety starter switch is your issue. The switch isnt recognizing the gear is in park so not allowing it to kick over.

Sent from my SM-G960U using Tapatalk
I wish it were that easy, but unfortunately that is not the case.

The ignition switch receives power from fuse M27. Should be a 10A fuse. You say the fuse is good but have you tested it with it in place? It's a mini fuse and should have little metal contacts exposed on the top of fuse that allow you to test it. Grab a test light, clamp it to battery negative. Then touch each side of the fuse leg...though those exposed holes on the top. Does the test light light on each side? If it does, then you have an issue from the right side of the fuse to the ignition switch. Could be wire, could even be part of the TIPM. If it lights on one side but not the other it's a bad fuse. If it doesn't light at all then something is not right in the TIPM (assuming the TIPM is getting power).
I actually did not look at the M27, and only changed the J17. I'm not a car whiz or anything, just know a little bit and Google the rest, and that is what everyone seemed to say to attack first.

M27 though, thanks for the tip! Will look into it.
 

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I'm going to add my 2 cents since I have been stranded 4 times with this issue, towed twice. Put the key in and turn it, all the dash light come on, but no start, and no click like a dead battery. It has always come down to the M27 Ignition Switch Power fuse, a red 10 amp fuse. The first 2 times the fuse had popped. Why would the fuse pop? The dealers answer was because of a loose negative terminal at the battery. The factory one just wouldn't cinch down tight enough. I never would have thought that not enough power would pop a fuse, but the second time around I had 4 or 5 fuses pop as soon as I reattached the negative cable after replacing the fuse. That prompted two #2. Was it the cause? I don't know but the dealers solution was to replace the battery terminal clamp (with what looks even cheaper that the stock one, a skinny stamped version). It solved it....for a while. I have had that fuse cause the problem twice more. Third time it popped, no idea why, good last night when it got parked, nothing the next morning. Changed the M27. Then this morning the same thing for the forth time, but this was a bit different. The fuse actually tested fine, as in it wasn't blown. But it made my tester swing different (noticeably faster harder needle movement on the tester than all the other fuses I tested in the fuse block). So I swapped it out a second time, and I am back to normal. I have no idea why that M27 fuse pops or causes problems, but it does. Since the second time it happened I have kept a card of 10 amp fuses (among other sizes) in the glove box, just in case. They helped this morning, but still not sure why the unblown fuse was a culprit. But I tossed it out just because. And made a note in my owners manual identifying M27.
 
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