2019 jlu ess not working/check engine loght

[adamkilcollins]

I have a 2019 jlu with manual transmission. 61000 miles.

last week the ess not working light came on and my highway gas mileage went to crap but vehicle seemed normal. It went off eventually and gas mileage went back to normal. Then the next day the check engine light came on after I got some gas. I disconnected the negative battery terminal and that reset the computer and everything was fine.

Today, the ess not working message came back on while driving on the highway and again, the mpg went to crap. On the same drive the check engine light came back on.


Battery issue/ESS battery issue? Any ideas?

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[aldo98229]

Start by replacing both batteries with an aftermarket brand.

Good luck.

 

[Jebiruph]

I have a 2019 jlu with manual transmission. 61000 miles.

last week the ess not working light came on and my highway gas mileage went to crap but vehicle seemed normal. It went off eventually and gas mileage went back to normal. Then the next day the check engine light came on after I got some gas. I disconnected the negative battery terminal and that reset the computer and everything was fine.

Today, the ess not working message came back on while driving on the highway and again, the mpg went to crap. On the same drive the check engine light came back on.


Battery issue/ESS battery issue? Any ideas?

If the ess light turns on while you are driving it's because there is an engine issue and ess is being disabled. This can happen before the engine issue hits the threshold that turns on the check engine light. Read the code when the check engine light turns on.

 

[Shibadog]

Start by replacing both batteries with an aftermarket brand.

Good luck.

What Aldo said. My money’s on the batteries being a tad funky.

 

[The Last Cowboy]

Gas mileage likely dropped due to the alternator running constantly. If you are on your original batteries, you are doing well at 4 years use out of them. Were there any other drivability issues?

 

[CaJLMetalHead]

I have a 2019 jlu with manual transmission. 61000 miles.

last week the ess not working light came on and my highway gas mileage went to crap but vehicle seemed normal. It went off eventually and gas mileage went back to normal. Then the next day the check engine light came on after I got some gas. I disconnected the negative battery terminal and that reset the computer and everything was fine.

Today, the ess not working message came back on while driving on the highway and again, the mpg went to crap. On the same drive the check engine light came back on.


Battery issue/ESS battery issue? Any ideas?

Define "gas mileage went to crap" I don't think ESS failure is going to significantly affect MPG unless you are stuck in the JL for hours in traffic with ESS turning the engine off...

One more thing.. do you take advantage of ESS? it not.. then you should remove that stupid ESS battery and run on the main battery only..

 

[adamkilcollins]

Yeah it's weird for sure. I do the same drive (95% highway) everyday and I routinely am at 20-24 mpg. As soon as the ess not working comes on, I'm struggling to stay at 18 and it's more likely 14-17 Mpg. Same drive, same time, roughly same wind conditions, same speedz, etc.

As soon as the ess not working lightl goes off, mpg goes back to 20-24.

 

[Yogi]

I have a 2019 jlu with manual transmission. 61000 miles.

last week the ess not working light came on and my highway gas mileage went to crap but vehicle seemed normal. It went off eventually and gas mileage went back to normal. Then the next day the check engine light came on after I got some gas. I disconnected the negative battery terminal and that reset the computer and everything was fine.

Today, the ess not working message came back on while driving on the highway and again, the mpg went to crap. On the same drive the check engine light came back on.


Battery issue/ESS battery issue? Any ideas?

Nothing, short of an EMP, will screw up a computer faster than low voltage, especially if it's erratic.
Like Aldo says ... replace the batteries.

 

[adamkilcollins]

Gas mileage likely dropped due to the alternator running constantly. If you are on your original batteries, you are doing well at 4 years use out of them. Were there any other drivability issues?

I replaced the batteries and both issues persist. The check engine light seems to be from a reported low voltage to O2 sensor (that's what the code reader says). Not sure if that could also affect the electric stop start.

 

[Jebiruph]

I replaced the batteries and both issues persist. The check engine light seems to be from a reported low voltage to O2 sensor (that's what the code reader says). Not sure if that could also affect the electric stop start.

Yes it can, ESS can get disabled when an engine issue is detected.

 

[adamkilcollins]

Yes it can, ESS can get disabled when an engine issue is detected.

Cool, thanks! Any experience changing o2 sensors? I can't find any diy videos on the internet (so far)

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