Service 4 whl drive light on

[wanderer]

So the other day that Light came on. And sway bar unavailable also came. And. Forward collision not available came on. I first ran an obd monitor and reset it he code and my start stop light went out and that started working. I though the ss battery was dead but I guess it wasn’t
So I unmarried the tazer. And that did not help all lights still on So off to the dealer it goes. Oh and. When I shift into 4/whl drive nothing happens it acts like it’s in 2 whl drive
Any thoughts?

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[Lunentucker]

$10 on the AUX battery

 

[wanderer]

i don't understand ? The aux battery ( start stop battery) shouldn't control the 4 whl drive system? it( start stop) started working again when I reset the code for it , but that was after the other lights came on.

 

[Hootbro]

Check the electrical connection to the FAD actuator on the front axle. If that is not connected properly or there is a problem with the FAD, it will disable the 4WD engagement.

The sway bar and forward collision messages are probably just cascading messages to the 4WD service message.

 

[ShadowsPapa]

i don't understand ? The aux battery ( start stop battery) shouldn't control the 4 whl drive system? it( start stop) started working again when I reset the code for it , but that was after the other lights came on.

Ignore almost all posts blaming the aux battery for things. It's because people don't understand what it does do, what it does not do and so on. It's nothing to do with anything once running except for the stop/start system. Once that engine is running, the charging system controls the voltage to things - not that silly battery that gets blamed for everything from global warming to your favorite NFL team losing to your wife's pants not fitting like they did 10 years ago.
Hootbro is generally closer to the truth on this stuff- he's good with electric.

If the system believes the FAD has not made a connection (whether is has or has not) then it will not allow the 4 wheel drive to fully engage. FAD must be connected before it can continue. I also believe that helps explain the sway bar bit.
ESS is also dependent on it being in 2 wheel drive among other things (a list of over 20 things have to fall into place or it can kick an error or cause that to not work)
So if there's an issue with the 4WD low mode, for one thing, goofy sh!# happens.

Frankly, almost everything you see out there about that little battery is slightly incorrect or just plain horribly wrong.

 

[wanderer]

Check the electrical connection to the FAD actuator on the front axle. If that is not connected properly or there is a problem with the FAD, it will disable the 4WD engagement.

The sway bar and forward collision messages are probably just cascading messages to the 4WD service message.

Great info, however, what and where is the FAD?

MY auto experience started 54 years ago when my dad bought me a push-button black Plymouth fury to rebuild which I did and after that went on to a 65 Corvair convertible with 4 single barrel carbs that had to be synched for it to run right. And while I have done some stuff on my jeep from a steering stabilizer to a snorkel and in my old jk added an unlocking device to the radio I consider myself a serious novice on my best day with newer modern stuff. Thanks

 

[ShadowsPapa]

Great info, however, what and where is the FAD?

MY auto experience started 54 years ago when my dad bought me a push-button black Plymouth fury to rebuild which I did and after that went on to a 65 Corvair convertible with 4 single barrel carbs that had to be synched for it to run right. And while I have done some stuff on my jeep from a steering stabilizer to a snorkel and in my old jk added an unlocking device to the radio I consider myself a serious novice on my best day with newer modern stuff. Thanks

Front Axle Disconnect. Between the punkin of the differential and the right wheel - in the right side front axle tube. It disconnects the two halves of the right front axle to reduce the drag and prevent the pinion and ring gear from turning when it's in 2wd.
AMC used that sort of setup for several years of the Eagle production, starting in 1981. In fact, they used the exact same vacuum motors to operate the FAD in Eagle as they did Jeeps of that era.

This is the 1980s version with a vacuum motor operating the disconnect/reconnect.

 

[Rusty PW]

The FAD is on the front axle. Between the pumpkin and the suspension point. It's the big cast iron piece. To get to the plug. The plug is on the back side of it. It's easier to remove the skid plate. I would unplug it, then plug it back in. Make sure it locks into place.

 

[Hootbro]

Great info, however, what and where is the FAD?

Attached pic stolen from the interweb. Red arrow points to the FAD assembly and connector. Like @Rusty PW mentioned, on back passenger side of the front axle.

The connector has a white secondary security tab as shown that needs to be gently pulled back and then you can squeeze the main connector release tab to remove it.

 

[wanderer]

Awesome if it stops Raining here I will crawl under and check it out thank you all so much

 

[jnack]

any update?

 

[wanderer]

Yes it was rodent damage

 

[Lost1wing]

Yes it was rodent damage

Any pics of what was chewed up?

 

[Rusty PW]

Yes it was rodent damage

Had a critter chew through a vent line on top of the gas tank on my Grand Cherokee a while back. Dealer wanted $600 for new parts. The tech fixed it with a piece of hose and 2 hose clamps.

 

[wanderer]

NO it was on tip of the transfer case . so I was told. by the dealer. I did see a ground squirrel around for a few weeks was meaning to trap it but I think some hawks may have got it first.

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