SERV 4WD - Dealership Is Stumped

[be77solo]

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[ShadowsPapa]

Keep us posted!

^^^^^^^
What he said.


I've seen some of that wiring while in the process of running the wires for my various "accessories".
I used to think it crazy to ever have a vehicle where a harness could not be replaced in a couple of hours or so......... then I saw some of those in this truck.

 

[Hootbro]

Well, the Tech sent test data to STAR per their request, and STAR says that there must be a short in the wiring harness going to the transfer case. They told me that the wiring harness can't be replaced without pulling out the engine/trans/transfer case or lifting the body off the frame. So, they are examining the harness for any obvious signs of damage, and then they will start unwrapping the harness to find the fault.

So, the Mojave will be spending Christmas at the dealership.

It amazes me as a whole how much there is a lack of good dealership technicians versed on electrical theory and the ability to troubleshoot and relying on engineering support that is hundreds if not thousands of miles away from the problem and does not have eyes on the problem.

The transfer case circuit wiring is not that complicated to disconnect everything to float the circuit and ohm out for wiring short to ground and/or to other wires on the circuit. In my world in aviation, this would be half a work shift worth of work for a avionics tech to get the harness ohm out and figured out if it is bad or good.

I feel for you dealing with dealership "Three Stooges" method of troubleshooting.

 

[ShadowsPapa]

Well, the Tech sent test data to STAR per their request, and STAR says that there must be a short in the wiring harness going to the transfer case. They told me that the wiring harness can't be replaced without pulling out the engine/trans/transfer case or lifting the body off the frame. So, they are examining the harness for any obvious signs of damage, and then they will start unwrapping the harness to find the fault.

So, the Mojave will be spending Christmas at the dealership.

Amazing how buzzwords get tossed around.
A "short" is technically where two sides of a circuit meet that should not meet - instead of the long way source to load to ground, it's a "short cut" source to ground.
A short indicates a hot wire making contact with something else.
That would require a cut in the insulation, or a worn spot. I can't see a need to unwrap a harness to find such a thing.
A harness would have to be really pinched hard, rubbed through insulation, or pinched/cut in a way to cause the conductor to touch ground or the conductor of another wire.

An open I could understand - a broken conductor with or without broken insulation.
An open could also be a pin pushed out of place in a connector, one side not making contact with the other side in the connector pair.

And if it's a CAN bus thing, harder to diagnose other than tracing with wires with an ohm meter, checking for continuity. Doesn't take a lot to interfere with a network situation. But that should generate errors related to CAN bus communication, invalid communication, lack of communication, etc.

I defer to Hootbro for more...........

But if it was me as a tech in a shop - simple first. Make sure you have end-to-end communications along each wire and that you don't have any wire contacting any other wire.
No different than tracking shorted or grounded poles in a starter armature.
A wiring harness won't be damaged where it's in the open. They don't need to waste time trying to find damage in some areas, it won't be there.

 

[jac04]

Thanks for the feedback @Hootbro and @ShadowsPapa

@Hootbro - I was looking at that wiring diagram too, thanks for posting it for all to see. I'm a ME, but automotive wiring isn't too hard to figure out. I was thinking that checking these circuits would be relatively straight forward, although probably a PITA.

If a wire is supposed to go from point A to point B, then check continuity from A to B, and check to make sure it doesn't have continuity to ground unless it is supposed to.

Anyhow, I'm hoping for the best, but spending part of my time off getting info together on the 'lemon' process. I hate to say it, but I'm also shopping for a new vehicle. I really like my JTM and don't want to feel forced to get something else, but I need to have a plan for the worst while hoping for the best.

 

[ShadowsPapa]

Thanks for the feedback @Hootbro and @ShadowsPapa

@Hootbro - I was looking at that wiring diagram too, thanks for posting it for all to see. I'm a ME, but automotive wiring isn't too hard to figure out. I was thinking that checking these circuits would be relatively straight forward, although probably a PITA.

If a wire is supposed to go from point A to point B, then check continuity from A to B, and check to make sure it doesn't have continuity to ground unless it is supposed to.

Anyhow, I'm hoping for the best, but spending part of my time off getting info together on the 'lemon' process. I hate to say it, but I'm also shopping for a new vehicle. I really like my JTM and don't want to feel forced to get something else, but I need to have a plan for the worst while hoping for the best.

One other thing to check - Make sure Wire #1 goes from A to B and not to ground but also make sure wire #1 doesn't go to Wire #2, #3 and so on.
Sometimes a fault isn't a "short" or ground, but is a contact with a wire it should not have contact with. I've seen harnesses that have been rubbed or even been hot, and two wires right next to each other had the insulation heated or thinned enough they contacted each other.
So wire #1 should be complete A to B but not to C, D, E, and so on (unless otherwise shown in the diagram)
I realize it's less likely today, with the improved wires and methods - but still..........

(ME, wow, you took it to the top. I was only licensed for maintenance for the city of Ankeny, otherwise did apprentice work but oddly, PFG somehow got around all of that and threw me into new office wiring. Here's the tools, here's the core drill - go wire these new offices. )

 

[MtnGladiator77]

My 'SERV 4WD' light came on. No check engine light or other lights. 2021 Mojave auto with Selec-Trac.

On my first trip to the dealership (3 weeks ago), they state that they checked for DTCs and "found DTC C140A-11 ", which is a code for Transfer Case Motor Performance. The service order also states that they did all the circuit troubleshooting for the transfer case control motor and wiring. They stated that the control module was shorted to ground internally and needed to be replaced, but was out of stock.

I looked up C140A online and found some information on the diagnostic troubleshooting steps. It basically says that if the circuits pass all the tests, then the problem has to be the control module.

This morning the control module was replaced (p/n 68483376AC) and guess what? The problem is still there.

Now the dealership says they have no idea what's wrong, so they can't fix it.

They opened up a Star Case and I'm going back for the 3rd time next week, but they're only plan is to do whatever the Star Case people tell them to.

Has anyone else been through this fiasco?

Thanks for the feedback @Hootbro and @ShadowsPapa

@Hootbro - I was looking at that wiring diagram too, thanks for posting it for all to see. I'm a ME, but automotive wiring isn't too hard to figure out. I was thinking that checking these circuits would be relatively straight forward, although probably a PITA.

If a wire is supposed to go from point A to point B, then check continuity from A to B, and check to make sure it doesn't have continuity to ground unless it is supposed to.

Anyhow, I'm hoping for the best, but spending part of my time off getting info together on the 'lemon' process. I hate to say it, but I'm also shopping for a new vehicle. I really like my JTM and don't want to feel forced to get something else, but I need to have a plan for the worst while hoping for the best.

I have a 2020 Rubicon and I've had the same issue, and the dealer says they never find anything wrong. Now my warranty is over, I'm assuming I will be stuck with a bill that has never been resolved. Has the dealer solved your issue? If so what did they come up with? Also when the service 4WD comes on does the cruise control stop working? My stops working, or doesn't turn on until I turn the motor off and back on to clear the problem

Thanks

 

[Lunentucker]

Now everyone's running to the "shorted wire" based on what some person who's never laid eyes on the vehicle says. ?

Anyone else notice that these messages from the great and powerful computers almost never mean what the message says?
It's usually a bad sensor, bent pin, bad wiring, etc.

Almost makes you want to find an old truck from the mid 80's and drive TF out of it until either greasy spot or an ungodly noise tells you, "Yeah, you really should SERV 4WD".

 

[jac04]

UPDATE:

They externally looked over the harness and didn't find anything, so they unwrapped the harness in 3 places to do spot-checks. Then STAR contacted them and said 'from the data you sent in, it is acting just like a bad shift control motor, check the motor'. When they checked the motor, they supposedly found an internal short.

Now, what really ticks me off is that the Tech stated that he followed all the troubleshooting steps for the C140a code during my original diagnostic visit. This was supposed to include checking the wiring AND the motor. My gut tells me that the Tech likely didn't check the motor , and only checked the wiring.

So, if the new control motor actually ends up fixing the problem I am going to give someone a talking to.

 

[jac04]

Has the dealer solved your issue? If so what did they come up with? Also when the service 4WD comes on does the cruise control stop working? My stops working, or doesn't turn on until I turn the motor off and back on to clear the problem

Check out my update above.

My SERV 4WD light is on constantly, and everything works perfectly fine except the vehicle never engages the front driveshaft and it also doesn't engage the FAD.

 

[jac04]

It's FIXED !!!!! They installed a new transfer case control motor.

I talked to the Shop Foreman, and he was very honest with me, which I appreciate.

It turns out that the Tech who originally did the troubleshooting did not follow all the diagnostic steps for the C140a code. He completely skipped the step of checking the transfer case control motor, and went directly to the end of the process, which was to replace the control module. The problem is that the paperwork filled out by the first Tech stated that he completed all the steps, which we now know is a lie.

While I had the Shop Foreman's attention, I mentioned that the original Tech cracked the rear trim panel for the inside of the cab. Without any further discussion, he ordered me a new one.

So, this whole frustrating process could have been resolved on the first visit (or second if they needed to order the motor) and less than a day of time working on it. Instead, it was 3 visits and a total of 10 days in the shop.

 

[Hootbro]

It's FIXED !!!!! They installed a new transfer case control motor.

Glad to hear.

Does not surprise me the tech skipped the troubleshooting steps and went to the bottom and shotgun a part that was incorrect.

 

[ShadowsPapa]

I have a 2020 Rubicon and I've had the same issue, and the dealer says they never find anything wrong. Now my warranty is over, I'm assuming I will be stuck with a bill that has never been resolved. Has the dealer solved your issue? If so what did they come up with? Also when the service 4WD comes on does the cruise control stop working? My stops working, or doesn't turn on until I turn the motor off and back on to clear the problem

Thanks

As long as there's a record of the same issue prior to warranty expiration, you've reported it, they've recorded your report, they've tried or looked at it - you would be covered.

 

[Lunentucker]

Great news!

 

[ShadowsPapa]

It's FIXED !!!!! They installed a new transfer case control motor.

I talked to the Shop Foreman, and he was very honest with me, which I appreciate.

It turns out that the Tech who originally did the troubleshooting did not follow all the diagnostic steps for the C140a code. He completely skipped the step of checking the transfer case control motor, and went directly to the end of the process, which was to replace the control module. The problem is that the paperwork filled out by the first Tech stated that he completed all the steps, which we now know is a lie.

While I had the Shop Foreman's attention, I mentioned that the original Tech cracked the rear trim panel for the inside of the cab. Without any further discussion, he ordered me a new one.

So, this whole frustrating process could have been resolved on the first visit (or second if they needed to order the motor) and less than a day of time working on it. Instead, it was 3 visits and a total of 10 days in the shop.

With luck the first guy, if he still works there, will be talked to.
Especially for warranty, you don't want to skip diagnostic steps or like FCA says "there may be a charge-back" if they see something was done improperly. They don't like buying parts that aren't needed.
I go back to the mirror example - shops are replacing the mirror assembly to take care of an ambient air temperature sensor issue. MOPAR says "don't do that" - if they discover the mirror is ok, or if they catch what the original complaint is and a mirror wasn't necessary, they'll charge the shop back for that assembly.
Bosses aren't happy when employees cost the shop money on charge-backs.

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