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Old 10-05-2019, 04:20 PM
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Check engine light turned off on its own?

Need some advice on my used 2015 Jeep Wrangler Unlimited Sahara.

Three weeks ago, the check engine light came on. When I checked the specific code it turned out to be the dreaded P0304 error: cylinder 4 misfire. Thinking it might be a fluke, I cleared the code and approx. 50 miles later the check engine light came back on with same code.

So, I called Jeep/Mopar to confirm my warranty. The basic has expired (obviously) but the powertrain has 11 months/67,000 left. My jeep has 33,000 miles on it so powertrain is covered.

Next, I called a local Jeep dealer, recommended by Jeep/Mopar and set up an appointment for this Monday. The service guy at the dealer warned me that it could simply be a problem with the spark plug or ignition coil. However, I don't have the expertise or wherewithal to go deep into the left side of my engine to figure this out, so I told them go ahead and schedule it.

Strangely, today I was driving around and noticed that the check engine light is no longer on. When I flick the key back and forth to aux, it no longer shows the error, either.

Does anyone know if the vehicle keeps a record of these codes in the onboard computer? I'm worried the dealership is not going to be able to do anything if the check engine light is off. I don't want to wait another week or so for the light to come back and would rather get the work done.

Thanks for any advice.

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Old 10-08-2019, 10:58 AM   #2
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Quote:
Originally Posted by Coolcat View Post
Need some advice on my used 2015 Jeep Wrangler Unlimited Sahara.

Three weeks ago, the check engine light came on. When I checked the specific code it turned out to be the dreaded P0304 error: cylinder 4 misfire. Thinking it might be a fluke, I cleared the code and approx. 50 miles later the check engine light came back on with same code.

So, I called Jeep/Mopar to confirm my warranty. The basic has expired (obviously) but the powertrain has 11 months/67,000 left. My jeep has 33,000 miles on it so powertrain is covered.

Next, I called a local Jeep dealer, recommended by Jeep/Mopar and set up an appointment for this Monday. The service guy at the dealer warned me that it could simply be a problem with the spark plug or ignition coil. However, I don't have the expertise or wherewithal to go deep into the left side of my engine to figure this out, so I told them go ahead and schedule it.

Strangely, today I was driving around and noticed that the check engine light is no longer on. When I flick the key back and forth to aux, it no longer shows the error, either.

Does anyone know if the vehicle keeps a record of these codes in the onboard computer? I'm worried the dealership is not going to be able to do anything if the check engine light is off. I don't want to wait another week or so for the light to come back and would rather get the work done.

Thanks for any advice.
Hello! Was the dealership able to assist you? If you have any questions, feel free to let us know.

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Old 10-08-2019, 01:11 PM   #3
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Quote:
Originally Posted by Coolcat View Post
Need some advice on my used 2015 Jeep Wrangler Unlimited Sahara.

Three weeks ago, the check engine light came on. When I checked the specific code it turned out to be the dreaded P0304 error: cylinder 4 misfire. Thinking it might be a fluke, I cleared the code and approx. 50 miles later the check engine light came back on with same code.

So, I called Jeep/Mopar to confirm my warranty. The basic has expired (obviously) but the powertrain has 11 months/67,000 left. My jeep has 33,000 miles on it so powertrain is covered.

Next, I called a local Jeep dealer, recommended by Jeep/Mopar and set up an appointment for this Monday. The service guy at the dealer warned me that it could simply be a problem with the spark plug or ignition coil. However, I don't have the expertise or wherewithal to go deep into the left side of my engine to figure this out, so I told them go ahead and schedule it.

Strangely, today I was driving around and noticed that the check engine light is no longer on. When I flick the key back and forth to aux, it no longer shows the error, either.

Does anyone know if the vehicle keeps a record of these codes in the onboard computer? I'm worried the dealership is not going to be able to do anything if the check engine light is off. I don't want to wait another week or so for the light to come back and would rather get the work done.

Thanks for any advice.

A misfire code will go out on its own if you have no more misfires within so many off/run cycles (can't remember how many off hand). There should be a record of it which is retained on the computer though.
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Old 10-08-2019, 01:54 PM   #4
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A misfire code will go out on its own if you have no more misfires within so many off/run cycles (can't remember how many off hand). There should be a record of it which is retained on the computer though.
Yep, this.
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Old 10-08-2019, 05:30 PM   #5
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Old 10-08-2019, 06:38 PM
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Thanks, for the replies everyone. The check engine light came back on as soon I pulled into the dealership service area -- how's that for timing? And, as people helpfully posted, the original codes were still in the system (all p0304).

The car is at the dealership now. . . for the 2nd day.

Direct quote from the service desk person is 'the tech is stumped.' They checked spark plugs and ignition coils and everything is working properly. I then asked about it being an issue with the cylinder head, as I have seen on other posts. Apparently, the tech does not think so.

Next steps are for a senior tech to now take a look. . .
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Old 10-09-2019, 10:37 AM   #7
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Originally Posted by Coolcat View Post
Thanks, for the replies everyone. The check engine light came back on as soon I pulled into the dealership service area -- how's that for timing? And, as people helpfully posted, the original codes were still in the system (all p0304).

The car is at the dealership now. . . for the 2nd day.

Direct quote from the service desk person is 'the tech is stumped.' They checked spark plugs and ignition coils and everything is working properly. I then asked about it being an issue with the cylinder head, as I have seen on other posts. Apparently, the tech does not think so.

Next steps are for a senior tech to now take a look. . .
If you'd like an extra layer of assistance while your Jeep is in at the dealership, feel free to send us a private message. I would be happy to connect you with a case manager to ensure everything gets resolved.

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Old 10-09-2019, 02:59 PM
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If you'd like an extra layer of assistance while your Jeep is in at the dealership, feel free to send us a private message. I would be happy to connect you with a case manager to ensure everything gets resolved.

Kaitlin
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Thank you, Kaitlin. I am going to see how it goes today. We are now on day 3. . .
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Old 10-10-2019, 10:51 PM
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If you'd like an extra layer of assistance while your Jeep is in at the dealership, feel free to send us a private message. I would be happy to connect you with a case manager to ensure everything gets resolved.

Kaitlin
Jeep Cares
We are in the 4th day of my Jeep being at the dealership and about about to go into the 5th. It is indeed a cylinder head issue that is covered by warranty (thankfully).

The dealership said they are trying to get me a loaner car but can't seem to find a Chrysler type vehicle as per warranty, according to them. I'd rather not go into the long weekend without a car.

Kaitlin, I pm'ed you about this and was wondering if there is any assistance you could provide. Thanks.
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Old 10-13-2019, 09:02 AM   #10
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A misfire code will go out on its own if you have no more misfires within so many off/run cycles (can't remember how many off hand). There should be a record of it which is retained on the computer though.
Yes this is correct. It should clear after 3 complete run cycles ( I wont define that right now) and it will also be stored in the computer.

- OBD Engineer
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Old 10-16-2019, 10:36 AM   #11
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The car is at the dealership now. . . for the 2nd day.
There's your problem. They're not really working on it until you stop calling it a car.
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Old 10-16-2019, 06:14 PM
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There's your problem. They're not really working on it until you stop calling it a car.

Haha!

So, I just started calling it a Jeep and lo and behold . . .my Jeep is back home with me where it belongs!

Seriously. . .
So happy it was under warranty. The total cost for repairs would have been over $2500 from the dealership. I did end up getting a rental car before the end of last week, which was also covered!
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Old 10-16-2019, 10:22 PM   #13
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The Jeep was throwing a fit over being considers a bland "car".
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Old 10-21-2019, 10:44 PM   #14
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Haha!

So, I just started calling it a Jeep and lo and behold . . .my Jeep is back home with me where it belongs!

Seriously. . .
So happy it was under warranty. The total cost for repairs would have been over $2500 from the dealership. I did end up getting a rental car before the end of last week, which was also covered!
What repairs was needed?
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Old 10-23-2019, 07:47 PM
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What repairs was needed?
Check out the attached file. . .

Basically it was the following:
- Cylinder Head
- Cylinder Head Gasket
- Cylinder Head Cover
- Gasket Intake Plenum
- Gasket Intake Manifold
- Gasket Chain Case Cover
- Gasket Exhaust Flange to Cylinder

Oil change and coolant.

Also, addressed passenger airbag inflator recall.
Attached Files
File Type: pdf New Doc 2019-10-23 13.13.12.pdf (594.8 KB, 8 views)
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Old 10-23-2019, 10:31 PM   #16
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This is interesting, i thought they had resolved this issue in the 2012-2013's with the recall. I haven't heard of any other 2013+ JK's having that same issue since the fix
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Old 10-24-2019, 12:18 PM
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This is interesting, i thought they had resolved this issue in the 2012-2013's with the recall. I haven't heard of any other 2013+ JK's having that same issue since the fix
Same here. Just glad everything was covered under warranty!

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