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Help! New 2018 JK won't always start

192K views 548 replies 141 participants last post by  Gscursel 
#1 ·
I have a brand new 2018 JK Sport that doesn’t always starts. I have taken it to the dealer but they haven’t been able to duplicate the issue. It has happened to me 4 times in a week. Usually only once per day. Here are the details.

2018 JKU Sport S. Automatic transmission, Auto locks and security system plus 430 radio.

Jeep starts no issue. I drive anywhere for 30-60 minutes straight and park and shut off the engine. I leave the jeep and lock the doors with the fob. When I unlock the doors and try to restart the Jeep everything powers up but the Jeep will not start. No ticking, not even trying to turn over. Just nothing. Jeep is in park and 2wd. After anywhere from 5 minutes to overnight the Jeep will eventually start again.

Unfortunately I haven’t been able to replicate the issue when at the dealership (go figure) but have recorded the problem. I will post video links below.

Most times the check engine light stays on but no code retained. One time the security system light flashed continuously.

Any guesses?

Videos
3rd time videos
https://youtu.be/G1XODe-v3LA
https://youtu.be/G1XODe-v3LA
https://youtu.be/3tfXBEtFYz8


4th time video
https://youtu.be/zW6Ihp3cwro
 
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#3 ·
Battery. Either the battery or the connections at the post.

I do not see the security light flashing. It is on when you first insert the key, but as the systems come on and the lights go out, the security light goes out as well. Besides, the SKIM does not keep the vehicle from starting, it just dies a few seconds later.

I would loosen the clamps a little bit, wiggle the clamps and then tighten them back up. Loose clamps or a failing battery can do weird things in the JK. It probably wouldn't hurt to take the battery to an auto parts store and have it load tested. They don't charge anything. If you have a voltmeter, you can check the voltage yourself, it should test at 12.6V or even a touch more. With the Jeep running it should be a little over 14 volts. But putting a voltmeter on it is NOT a load test.

I know it's a new Jeep, but the battery is a purchased item and the supplier may not have the standards of an Odessy battery.

When this happens, have you tried jump starting the Jeep?

I just had to replace the battery in my TJ (it was 5 years old) and it reacted similarly. I would go out, turn the key on and all the lights would light up, the secure key light would go out, I would turn the key and everything would go black. Nada. But, I could jump it off. But, this was cold, and once it had been running a bit, it would start normally, but the battery would not hold a charge.

It does not do it every time you drive it - or does it?
 
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#5 ·
When the battery starts to go bad the jeep does funky stuff, mine did.
 
#9 ·
Have you tried using the other key? It feels very much like the security system isn't allowing the computer to send start commands to the vehicle (the ignition is really just a button anymore that sends start commands) so mechanically it would be rare that the ignition in the column would be the issue.

I would try the 2nd key that came with the vehicle and see if the issue persists. It could be a stupid issue with the chip in your Key Fob working randomly (twisting in your pocket or something could make for sporadic functioning). Without a key programmed to your vehicle (which only the dealer can really do) the car would perform exactly like you are describing. what makes me think this is that issue is the occasional flashing of the security system LED as you stated.

Give that a shot if you have not already.

I had this issue in my old Jeep Cherokee sport (but that thing had 280K miles on it and was constantly an electrical nightmare for the last 30K miles) so it was not key related.
 
#10 ·
OP here. Thanks everyone for the suggestions. The dealer had the Jeep for 2 days last week and put about 50 miles on and were unable to replicate the problem. I picked it up Thursday and have driven it about 2 dozen times over the weekend with no more occurrences. The dealer says that my Mobil speed pass could have messed with the immobilized but there is no way to tell. Regardless I no longer have it on my key ring. It seems they did disconnect the battery and as the radio had reset.

I’m hopeful that the gremlin has been chased off and I can enjoy the jeep I’ve been wanting for 20+ years.
 
#13 ·
starter solenoid, bad battery, bad ground, or bad battery connections
 
#14 ·
Well it happened again last night. Same situation as the 1st time. Started no issues and drove 50 miles. Parked at a store for 10 minutes. Returned and it wouldn’t start. Jumping it made no difference. Neither did disconnecting and reconnecting the battery. Had to leave it overnight and will try again today but heading back to the dealer after work.
 
#16 ·
Personally, I would have called the dealer and had them come get it when it would not start. You should have roadside assistance with your Jeep. If they have to come get it every time, maybe they will have a better incentive to fix it.
 
#15 ·
Could have something to do with the key. Maybe the security system isn't recognizing the chip in the key intermittently. Did you get 2 keys when you purchased? Have you tried them both?

EDIT: Sorry this was already addressed in post #9. That's what I get for posting before actually reading through the thread.
 
#17 ·
How many times at the dealer? Sounds like at least 3. In Florida, the law is....

"The Florida lemon law requires the manufacturer to repurchase or replace a car that meets a certain warranty repair history. Specifically, the Florida lemon law states that if a consumer has presented a car for the same recurring defect three or more times or the car has been in an authorized repair facility 15 or more days (this can be for different repairs and the days do not have to be consecutive), the consumer can then pursuant to the Florida lemon law statute provide written notification to the manufacturer that it has a final opportunity to repair the car."

Your state might have something similar. If so, bring the Jeep to the dealer along with a letter stating the history of the problem and reference the states lemon law. That will get there attention. They will give you a rental and hold on to it until they are sure it is fixed. Good Luck.
 
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#20 ·
This is probably way off base here. I responded to this because I had the same issue when I first bought my Jeep. The first upgrade I did was to have a new stereo installed. They used the tensioning nut on the battery terminal to mount the power for the new stereo (sadly, not the most disappointing part of the stereo install) But I had intermittent starting issues and couldn't put my finger on it, until I looked a little closer. The harness was on the terminal and it appeared to be making contact. I would really look at the battery cables and terminals.
 
#457 ·
No Crank no start after thruway driving



I have the same problem too. I have a 2018 JKU Rubicon. This only happens after Highway speeds and then after getting to my destination soon after I am only able to start Jeep after 25 minutes of rest. This has happened 5 times since I purchased in March 2019 with 9K miles on it. Right now I am trying to track any trends related to Transmission temperature and any correlation to a no crank issue. I do not have this problem in local city driving.
 
#24 ·
Sounds silly, but how fast are you turning the key after putting into ignition? Reason I ask is because a week a ago I had the same symptom as you. I put in the key and turned it instantly and I got nothin, waiting a few seconds and then it worked.
I make sure to turn the key 2 clicks now and wait for it to chime 2-3 times before I turn the key
 
#25 ·
OP here. Still having the same issue however I have been able to narrow down the source of the issue. The dealer has not been able to fix the problem yet, though. The dealers 1st repair was to replace the Wireless Control Module (WCM), but 2 days later I had the same no start.

Here's what I've determined:

The failure to start is actually by design and is not a problem with the key, security system or ignition. During all of my own diagnosis (not the dealers) I figured out that the Transmission Control Module (TCM) monitors a contact switch wired in series with the transmission temperature sensor to determine PARK and NEUTRAL positions. The TCM broadcasts the sensor position to the PCM which in turn allows operation of the starter circuit. If the TCM does not get the signal that the transmission is on P or N, the PCM will not a the Jeep to start. The TCM is either not getting the signal due to a bad sensor wire, or the TCM itself is bad. There is a difference between Shift Lever position, which is displayed on the instrument cluster and contact switch wired in series with the transmission temperature sensor to determine PARK and NEUTRAL positions.

The instrument cluster can display transmission temperature (Menu->Vehicle Info->Trans Temp). When the Jeep is in R or D, the transmission temp is displayed (~160 deg hot), however when in P or N, the temperature changes to engine temp (~220 deg hot). Only the temperature changes, not the words "Trans Temp".

I've been monitoring the display and now see that whenever the Jeep doesn't start, the temperature hasn't changed. In fact, I now know that if the temp doesn't change I shouldn't tuen off the Jeep as it isn't going to start. I've been able to get the Jeep to start by moving the shift lever back and forth between P and D several time and rolling the Jeep a bit. It sometimes takes a few tries, sometimes 5 minutes.

Here's a link to all of the videos I've taken.

http://www.youtube.com/playlist?list=PLvpaml2Br4G_xwRHxU2bHjmnTkmiijERV

No start #12 was the 1st time I notice the temp changed which resulted in the Jeep starting (1:56). No start #17a & B (wife called during recording!!!) shows the full issue from coming to a stop and putting the Jeep in P, the temp doesn't change and the Jeep doesn't restart. After about 4 minutes of moving the Shift Lever and rolling the Jeep down the driveway the temp finally jumps (#17b 0:55) and I am able to start the Jeep and drive away.

I've presented all of this to the dealer, Chrysler Customer Care and a Chrysler Field director. The field guy came down this week. They took the Jeep and replaced the Total Integrated Power Module (TIPM), which controls everything. They claimed this had fixed it, and the very next day I had the same issue.
 
#498 ·
Some more info:
ATF Temperature Sensor:
The ATF temperature sensor is a positive temperature co-efficient (PTC) Thermistor. It measures the temperature of the transmission fluid and is a direct input signal for the TCM. The temperature of the ATF has an influence on the shift time and resulting shift quality. As the temperature rises, resistance rises, and therefore, the probing voltage is decreasing. Because of its registration, the shifting process can be optimized in all temperature ranges.

The ATF temperature sensor is wired in series with the park/neutral contact. The temperature signal is transmitted to the TCM only when the reed contact of the park/neutral contact is closed because the TCM only reads ATF temperature while in any forward gear, or REVERSE. When the transmission is in PARK or NEUTRAL, the TCM will substitute the engine temperature for the ATF temperature.

Starter Interlock
The TCM monitors a contact switch wired in series with the transmission temperature sensor to determine PARK and NEUTRAL positions. The contact switch is open in PARK and NEUTRAL. The TCM senses transmission temperature as high (switch supply voltage), confirming switch status as open. The TCM then broadcasts a message over CAN bus to confirm switch status. The PCM receives this information and allows operation of the starter circuit.
This is ALOT of information!!! Where did you find out this diagnosis stuff? I am betting with this info, you are 10X smarter than 90% of the "Factory Trained Gorillas" working in most Stealerships. Is there a shop manual or some other book you gleaned this information from?
 
#26 ·
Some more info:
ATF Temperature Sensor:
The ATF temperature sensor is a positive temperature co-efficient (PTC) Thermistor. It measures the temperature of the transmission fluid and is a direct input signal for the TCM. The temperature of the ATF has an influence on the shift time and resulting shift quality. As the temperature rises, resistance rises, and therefore, the probing voltage is decreasing. Because of its registration, the shifting process can be optimized in all temperature ranges.

The ATF temperature sensor is wired in series with the park/neutral contact. The temperature signal is transmitted to the TCM only when the reed contact of the park/neutral contact is closed because the TCM only reads ATF temperature while in any forward gear, or REVERSE. When the transmission is in PARK or NEUTRAL, the TCM will substitute the engine temperature for the ATF temperature.

Starter Interlock
The TCM monitors a contact switch wired in series with the transmission temperature sensor to determine PARK and NEUTRAL positions. The contact switch is open in PARK and NEUTRAL. The TCM senses transmission temperature as high (switch supply voltage), confirming switch status as open. The TCM then broadcasts a message over CAN bus to confirm switch status. The PCM receives this information and allows operation of the starter circuit.
 
#31 ·
Same issue for me. I just got my new 2018 jk last week and it has done this to me on two different occasions. I don’t even have 500 miles on it yet. After a few minutes it has eventually started. I am supposed to take it in to be looked at by the dealership the beginning of the week. I also fear they won’t be able to duplicate it. I even called road side assistance the first time but then it eventually started. I absolutely love my new Jeep but am really hoping this issue can be resolved. I double checked everything the second time it did it. I was definitely in park. The lights and radio would work but it wouldn’t even attempt to turn over. The engine light came on during the non start too. I haven’t been paying attention to which key I am using so maybe I should keep track. I’m going to start taking video when it happens so that I have proof.
 
#32 ·
Transmission Range Sensor,( Neutral Safety Switch) if it is still in the Transmission. Mine went out, had to shift to neutral and park again, or just neutral to start it. Mine is a 07' though, not sure if same switch is still being used.

If it is temperature related it always comes down to the Crankshaft position sensor, has to cool down before starting back up. i would think Jeep had those ironed out by now.
 
#35 ·
Transmission Range Sensor,( Neutral Safety Switch)
If it is temperature related it always comes down to the Crankshaft position sensor, has to cool down before starting back up. i would think Jeep had those ironed out by now.
Crankshaft position sensor. Its a sensor problem. Heats up and fails.
 
#36 ·
What was the driving condition prior to the failure to restart? Mine is consistently after driving on the highway. Happened again today. Also, are you monitoring the transmission temp on the instrument cluster. This is now the indication that I use to know it won’t start. If the temp doesn’t change i move the car some more.

As for the starter swap if you are having the same problem as me then this won’t help. The issue is almost certainly with the transmission position sensor.

Let us know how it goes.
 
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