Internal Fuses in the PDC

[Helloh2u]

I wanted to wait until my JLUR was repaired and back in my hand before posting this. I recently had my Jeep in the shop for about 10 days with an electrical issue that left me stranded on the side of the road. After the first day, the dealer informed me that the Aux battery had died and that they replaced it but wanted to hold it overnight to make sure everything was ok. The next morning they told me that the battery had died again because something was drawing a charge on the battery. After emailing back and forth with the service adviser at my dealership, I was informed that during the course of their troubleshooting, which included working directly with FCA engineers, the shop was informed that there are actually internal fuses in the PDC that are not replaceable without replacing the entire PDC.

I have a theory as to why the fuse popped but since the dealership gave a me a free rental and charged me zero dollars for the repair (which makes sense since the Jeep went in with 8200 miles), I will just let it go.

All that to say, if for some reason your shop finds that there is a draw on the batter that they cannot pinpoint and none of the fuses in the PDC seemed damaged, there are a few inaccessible fused in the PDC that will require the entire PDC to be replaced.

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[Rhinebeck01]

@Helloh2u

On edit 2/19/21 DO know that there are 2 different fuse arrays for the JL/JT that you can buy. IF you have the tow package you need to use 68368854AA Mopar Z Case Fuse Array, not the 68368853AA Mopar Z Case Fuse Array

Your post is totally inaccurate, unfortunately. That fuse array in the PDC is in fact replaceable and your stupid service department just did not know it. Your PDC did not need to be replaced!

Below see a pic of the fuse array ($59+-) that could have been replaced as it is replaceable. Also see a pic with it's part number.

Take the info below to the stealership and tell them to shove it up their arse.. No reason to have had your JL at their shop that long.

Fuse array

Part # and... part is readily available...

Fingers pointing to the installed, replaceable fuse array in the PDC

.

 

[Jebiruph]

All that to say, if for some reason your shop finds that there is a draw on the batter that they cannot pinpoint and none of the fuses in the PDC seemed damaged, there are a few inaccessible fused in the PDC that will require the entire PDC to be replaced.

Since a good fuse is a dead short and a blown fuse is an open circuit, I don't see how a blown fuse could cause a draw on the battery. Per the related Jeep Informant video, if the techs removed the positive battery terminal and let it short to ground, it would blow the fuse in the fuse array that connects the aux battery to the main battery/alternator output. This isolates the aux battery that, according to the schematic powers the radio frequency hub, which is probably what drained it.

 

[RussJeep1]

A couple of things. To my understanding, @Rhinebeck01 is certainly factual about the notion that damage to any one or more of the high end fuses in the strip that occupies the driver's side most side of the Power Distribution Center (PDC) can be remedied by purchase of a replacement fuse bar, if it is in fact these fuses we are referring to. The far more expensive PDC in its entirety, which subsumes these fuses, need not be replaced in such circumstances.

BTW: in case it wasn't stated, blowing as little as one of these high end fuses in the bar requires replacement, I'm told, of the entire bar, but again, not the entire and far more expensive PDC.


@Jebiruph Jerry: I wonder (in other words I don't by any means know for certain)..

...if the shorting of the main battery as you describe indeed blew the fuse that allows the ESS battery to be recharged when the engine is on, I question not only if

* the rig could crank in the first place with this blown fuse--or if it could--

* simply function until the rig was turned off,

but what might have caused the new ESS battery to lose current overnight. It's my understanding that the ESS battery powers the rig's accessories during the duration of an ESS shutdown, which itself would not occur, or be sustained, if the [properly functioning] rig was powered down overnight, or even if the rig was "on" ("on" not necessarily implying that the engine is idling or not as the rig could be at some ESS event with the engine off,) the rig's computer sensed the ESS battery not capable of meeting the rig's electrical demand while motioness but "on."

In such case, the rig would restart, even if still in the motionless state that brought auto stop to manifest in the first place.

Of course the key words above are "properly functioning rig."

Cranked: its definition needs refinement for a vehicle with autostart/stop and/or hybrid or electrical systems. In the old days "cranked" met an engine successfully idling; "turning over" if you will.

Today, with ESS or battery powered or hybrid vehicles, cranked means the rig is capable of propulsion and maintenance of its electric draw for accessories and/or said propulsion as a result of pushing a start button or turning a key that may or may not result in the engine actually idling or "tuning" over if you will.

I need a better word (maybe simply "on" and "off") to describe a vehicle's state, independent of whether, with ESS, or other non fossil fuel power sources, the engine is idling at any given moment.

Electrical things are bound to get more complicated with the semi hybrid model as well as the 2.0L model and its 48V battery.

 

[RubenZ]

This is why dealers suck. I know our JEEPS have warranty but I will almost always research youtube or forums to find fixes for issues before even going to dealership. Or to arm myself with some knowledge before going. These service departments most of the time don't know what the hell they are doing. They can't possibly be trained properly on all these new vehicles and most of the time they follow the guidelines of INDIAN CALL CENTERS. just go down a stupid flow chart trying to figure solutions out.

 

[Rhinebeck01]

@RussJeep1

Your post made a thread that was not confusing, confusing. 8-( Ya know, sometimes if you really don't know, it is best just to not post anything.

Learn what the JL/JLU PDC is all about and you will know that there is no other possibility then that fuse array... geeeeeeeeeeeez.

p.s. And no, I do not rely on YouTube videos to educate me. And I only comment / post if I know for sure.

 

[Jebiruph]

A couple of things. To my understanding, @Rhinebeck01 is certainly factual about the notion that damage to any one or more of the high end fuses in the strip that occupies the driver's side most side of the Power Distribution Center (PDC) can be remedied by purchase of a replacement fuse bar, if it is in fact these fuses we are referring to. The far more expensive PDC in its entirety, which subsumes these fuses, need not be replaced in such circumstances.

BTW: in case it wasn't stated, blowing as little as one of these high end fuses in the bar requires replacement, I'm told, of the entire bar, but again, not the entire and far more expensive PDC.


@Jebiruph Jerry: I wonder (in other words I don't by any means know for certain)..

...if the shorting of the main battery as you describe indeed blew the fuse that allows the ESS battery to be recharged when the engine is on, I question not only if

* the rig could crank in the first place with this blown fuse--or if it could--

* simply function until the rig was turned off,

but what might have caused the new ESS battery to lose current overnight. It's my understanding that the ESS battery powers the rig's accessories during the duration of an ESS shutdown, which itself would not occur, or be sustained, if the [properly functioning] rig was powered down overnight, or even if the rig was "on" ("on" not necessarily implying that the engine is idling or not as the rig could be at some ESS event with the engine off,) the rig's computer sensed the ESS battery not capable of meeting the rig's electrical demand while motioness but "on."

In such case, the rig would restart, even if still in the motionless state that brought auto stop to manifest in the first place.

Of course the key words above are "properly functioning rig."

Cranked: its definition needs refinement for a vehicle with autostart/stop and/or hybrid or electrical systems. In the old days "cranked" met an engine successfully idling; "turning over" if you will.

Today, with ESS or battery powered or hybrid vehicles, cranked means the rig is capable of propulsion and maintenance of its electric draw for accessories and/or said propulsion as a result of pushing a start button or turning a key that may or may not result in the engine actually idling or "tuning" over if you will.

I need a better word (maybe simply "on" and "off") to describe a vehicle's state, independent of whether, with ESS, or other non fossil fuel power sources, the engine is idling at any given moment.

Electrical things are bound to get more complicated with the semi hybrid model as well as the 2.0L model and its 48V battery.

Based on my current theory of how the system works (and I don't have any information that hasn't already be posted on this site), here's my explanation and answer to your questions.

First, every time I've checked battery voltages running or not (but not auto stopped), both batteries measure exactly the same. This indicates to me that the batteries are connected through the PCR (Power Control Relay) and I believe that is the normal condition. According to how I read the schematic (posted else where), the PCR and critical starting electronics (start switch and fob related electronics) all run directly off of the aux battery.

So under normal conditions with both batteries connected (PCR engaged), the main battery assists the aux battery to supply power to the starting related electronics. If the aux battery dies or lacks sufficient power, the PCR (powered by the aux battery) cannot connect the batteries, which is why you are completely dead with a bad aux, but good main battery.

If the dealer replaces a bad aux battery with a good one, but accidentally shorts the main battery terminal to ground (blowing PCR fuse), the new aux battery is isolated from the main battery and the alternator so everything will work until the aux battery loses it's charge. The drain on the aux battery is module that communicates with the fob, which is always drawing power.

I am not convinced there is any mechanism that monitors the aux battery and prevents a start if the battery is low, I think it's the low battery that prevents the start.

 

[RussJeep1]

If the dealer replaces a bad aux battery with a good one, but accidentally shorts the main battery terminal to ground (blowing PCR fuse), the new aux battery is isolated from the main battery and the alternator so everything will work until the aux battery loses it's charge.

Sounds entirely plausible Jerry, but I'm sure you'd agree not consistent with overnight, rig off, deenergization of the ESS battery: consistent with some circuit fault that's tapping the ESS battery at rest.

 

[Jebiruph]

Sounds entirely plausible Jerry, but I'm sure you'd agree not consistent with overnight, rig off, deenergization of the ESS battery: consistent with some circuit fault that's tapping the ESS battery at rest.

I would expect them to start the vehicle with the new battery installed. So unknown to them, the whole time the vehicle is running, the new battery is running down. The next day when they try it, it's too drained to start.

 

[RussJeep1]

I would expect them to start the vehicle with the new battery installed. So unknown to them, the whole time the vehicle is running, the new battery is running down. The next day when they try it, it's too drained to start.

Would you not agree Jerry @Jebiruph that simply starting the rig with the fresh ESS battery, even if its not charging say due to shot fuses like you describe, might not be enough to drain it of adequate juice simply by virtue of the ESS operating accessories (which it is my understanding, not fact, it does when the ESS is engaged), and that if its death the next morning leads to inability to turn the rig over, that we might be dealing with a faulting electrical component taxing of the ESS beyond spec perhaps even in addition to the rig not charging it while the engine is on and ESS off?

 

[Jebiruph]

Would you not agree Jerry @Jebiruph that simply starting the rig with the fresh ESS battery, even if its not charging say due to shot fuses like you describe, might not be enough to drain it of adequate juice simply by virtue of the ESS operating accessories (which it is my understanding, not fact, it does when the ESS is engaged), and that if its death the next morning leads to inability to turn the rig over, that we might be dealing with a faulting electrical component taxing of the ESS beyond spec perhaps even in addition to the rig not charging it while the engine is on and ESS off?

Under normal operation, an auto stopped engine will restart after 5 min., so that could be considered a safe time to run on the aux battery. How much of a charge does a new, off the shelf aux battery have, 60 -70%? So how long is a safe time to run on that? When they put the new aux battery in, how long do they let it run to check it out? If they were getting an error condition, they would have had it running even longer while they investigated. I think they ran on the aux battery too long and ran it down.

According to the dealer, the problem was resolved by replacing the entire PDC because of a blown fuse and nothing else was mentioned. This is exactly the issue JeepInformant addresses in his Don't be Robbed by Ignorance video. The OP has a theory about the popped fuse, but unless more information is provided, this is the best explanation in my opinion.

 

[Agnes]

Hi I have similar problem with my JL 3.6. I can start a car.
The battery was replaced because the previous one was torn out from underneath. We installed a new battery started the engine, everything was ok and on the second day the battery was discharged and there was no possibility to start. Maybe it is that fuse array in the PDC? What do you think? I will be gradefull for help.

 

[Jebiruph]

Hi I have similar problem with my JL 3.6. I can start a car.
The battery was replaced because the previous one was torn out from underneath. We installed a new battery started the engine, everything was ok and on the second day the battery was discharged and there was no possibility to start. Maybe it is that fuse array in the PDC? What do you think? I will be gradefull for help.

Are you sure it's a dead battery, what are the symptoms?

 

[Agnes]

I change the fuse array in the PDC and its start

 

[Faresalsal]

I just encountered this issue with my 2019 JL Rubicon, the dealership stated that the fuse is blown and will need to be replaced. I’m based in “Kuwait” and the part isn’t available here and will need to be overnighted from overseas.

i had shut off the jeep to go to a supermarket and it wouldn’t turn back on.. kept trying until it started and gave me all kinds of warnings..

the dealership ran a test on both batteries and they are fine and determined that the fuse is blow.. will receive the jeep back after the part arrives

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