Engine Cold, Fan roaring, No stop/start

[cjaama]

I haven’t been driving my JL much lately and when I have, it’s been a lot of city driving. This morning I got in and it hesitated slightly more than normal. I didn’t think anything of it, since it has been a couple days since I last drove it. Drove fine, stop/start worked at one of the lights before reaching the highway. Got on the highway and the “stop/start unavailable” indicator came on (again, I wasn’t surprised, since I have been doing more city than highway driving lately). When I got off the highway, I noticed the fan was running really loud, then looked and the temperature gauge was all the way down at “C”. Ambient temperature is 72 and muggy. I turned the A/C off, but this didn’t have any effect.

I’ve read about people saying their fan is really loud. I’ve never had my fan run at this speed/volume. I could hear it over the radio with the windows up. It was humming!

I have had the stop/start unavailable before, which lead to me having both batteries replaced. I know most dislike start/stop, I actually do.

Anyone have any clues?

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[GATORB8]

May want to check and see if you have any codes, engine running straight cold use to point to a T-stat stuck open, but probably electronically controlled now.

 

[cjaama]

May want to check and see if you have any codes, engine running straight cold use to point to a T-stat stuck open, but probably electronically controlled now.

No check engine lights, but I can't say anything beyond that.

 

[GATORB8]

No check engine lights, but I can't say anything beyond that.

Do you have a code reader? May be able to see a pending code if it keeps doing this.

 

[Jebiruph]

I haven’t been driving my JL much lately and when I have, it’s been a lot of city driving. This morning I got in and it hesitated slightly more than normal. I didn’t think anything of it, since it has been a couple days since I last drove it. Drove fine, stop/start worked at one of the lights before reaching the highway. Got on the highway and the “stop/start unavailable” indicator came on (again, I wasn’t surprised, since I have been doing more city than highway driving lately). When I got off the highway, I noticed the fan was running really loud, then looked and the temperature gauge was all the way down at “C”. Ambient temperature is 72 and muggy. I turned the A/C off, but this didn’t have any effect.

I’ve read about people saying their fan is really loud. I’ve never had my fan run at this speed/volume. I could hear it over the radio with the windows up. It was humming!

I have had the stop/start unavailable before, which lead to me having both batteries replaced. I know most dislike start/stop, I actually do.

Anyone have any clues?

It looks like the full speed fans and disabled ESS are in response to a bad water temperature sensor.

 

[cjaama]

I just took the Jeep for a ride and it didn't not reoccur. Start/stop was even working. Hopefully it was just a glitch in the matrix.

 

[M487]

I kn

I just took the Jeep for a ride and it didn't not reoccur. Start/stop was even working. Hopefully it was just a glitch in the matrix.

I know this thread is a bit old, but I just started looking for someone who had these issues--because I just recently experienced the same thing with my 2020 JLUR. The "A" dash light comes on, no temperature reading, and a very loud fan noise starts up. All disappeared when the engine is turned off and then on, but all came back again, and off/on again intermittently. After a few times the CEL came on, and stayed on. A dealer had the Jeep for almost a week, never duplicated the issues, but replaced both batteries and, of course, reset the CEL.

Now, just a few days from the dealer, all three issues are back again. The CEL isn't yet on, but I was able to drive to a different dealer and the service advisor did witness the three issues for herself. She ran some diagnostics, and will be taking in the Jeep soon.

My biggest concern is that the three issues could be an indication of future escalation. So, to help with the diagnosis and cure, has anyone found the solution?

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