Low voltage on the 3.6?

texastonka

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Alright friends! I got a strange question about the new JL. Now this thing has the maddening stop/start crap (for now), but the voltage concerned me.
Under throttle and idle voltage is at a low 12.6V, now if I’m going down the road and coast voltage will go up to 13.2-13.4. It never hits what I consider normal at 14.1+ with a good alternator.
I took to auto parts store to have tested. Battery passed, starter failed, voltage regulator failed.
Question is to anyone with a JL with stop/start junk, is your voltage just as low and weird?

If so this is going to really be crappy with a Warn 16.5ti pulling me out of a bad situation.

Dealer has no idea what the voltage SHOULD be, basically saying wait for a failure. I like to be more proactive than that.

Any help is much appreciated.
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Rhinebeck01

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@texastonka

What you are seeing is typical for the 3.6L JL. Other JL owner's are seeing the same as you. If, they aren't, then there is an issue with their JL.
 

WranglerMan

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This has been discussed more times in the past year than I can remember and I am one of the top posters on this behaviors, unofficially as in no documentation from FCA I have been told that voltsge can run from 12.6-14.5 and it depends on the the battery needs in regard to a charge, those that are seeing 14.4 all the time may have an issue from what several techs have told me.

If you run a search on this here you will find lots of posts and even voltsge testing I have done

Here is a display of my JLU Sahara EVIC voltage display and it’s normal, and remember what you see in the EVIC has the influence of the alternator involved as a fully charged battery is 12.66 and the only way to get the voltage is directly off the battery with a meter

 

1quick1

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My OBD shows an P0007 which is some sort of voltage issue that doesn't trigger a CEL.
 

W1ck3d

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That voltage on the cluster is displaying the charge from the alternator to the battery.. . Not the battery voltage
 

WranglerMan

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That voltage on the cluster is displaying the charge from the alternator to the battery.. . Not the battery voltage
Only to a certain degree,a good example is I just pulled my JL off the trickle charger and historically coming off the charger the battery voltage usually runs 13.2+ for aleast a day and that’s what is displayed in EVIC and this can be checked with a meter directly at the battery and the alternator is putting out no voltage as the IBS is telling it that the battery is 100% and as the voltage drops and gets to the 12.5-12.7 range is when the EVIC voltage starts to change and the alternator is then sending small charges to the battery and the more ESS is utilized the higher the displayed voltage reading will be.
 

Jebiruph

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The voltage displayed on the cluster is the current system voltage. If the engine is off, it will be the battery voltage. When the engine is on, it will be alternator voltage because the alternator voltage will be the system voltage. The alternator output is controlled by the Powertrain Control Module based on current load and whatever other factors are programmed into the system.
 

WranglerMan

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@Jebiruph so as the IBS monitors the voltage does it tell the PCM what to do based on the needs of the vehicle thru the CAN Bus ?
 

Jebiruph

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I assume the PCM utilizes some IBS data, especially battery health, to set alternator output. A discharged battery normally places additional load on the alternator, this additional load is automatically sensed by the PCM and alternator output is adjusted, so IBS data regarding the battery state of charge may not be needed.
 

W1ck3d

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@Jebiruph so as the IBS monitors the voltage does it tell the PCM what to do based on the needs of the vehicle thru the CAN Bus ?

The ibs data is stored in the bcm... Then the bcm directs the car what to do based on the charge... Id have to look at the schematics, but i know battery data is stored in the bcm
 

Jebiruph

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The ibs data is stored in the bcm... Then the bcm directs the car what to do based on the charge... Id have to look at the schematics, but i know battery data is stored in the bcm
Sorry @WranglerMan, I missed the last part of your question regarding the CAN bus. @W1ck3d is right that the IBS is connected to the BCM. The main purpose of the IBS is to provide data related to ESS system. I would assume that the BCM can provide battery related data to the PCM that could affect alternator output if the engineers wanted it. For instance, as the health of the battery degrades and it becomes more difficult to charge, it may be desirable to increase the output of the alternator to compensate.
 
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