Error codes U0001 and U0401 on a 2020 Gladiator Overland

[RobCart]

Hi All.
I need your thoughts. I'm a 2020 Gladiator Overland with 39k miles. I've been in and out of the dealer with error codes since around 25k to 28k. On Sept 1st it went in to the dealer with 37k for a shifting issue that occurred while wheeling. After about 1.5weeks they called to say it was ready. They replaced the transmission. While driving home the error message came up Service Shifter. This would display around 12 times during my hr drive home. Over the next few weeks this message would pop up again a few more times. Back to the dealer we go. Now since it's over 36k miles on it they claim it's possibly electrical and they need $600 to diagnose it. if it turns out to be powertrain they will wave the fee as it's still under powertrain warranty. It has been there since Oct 11th. Today they call me right at closing to say in order to continue diagnosing that I need approve 2k more and that they need to remove all my aftermarket electrical gear. Winch connected directly to the battery, three of the aux switches are in use. Oracle headlights and tail lights.that are plug and play, lastfit switches and rock lights that are wired to a bluesea Fuze box with the positive to battery and negative to chasis where the manual states to connect the negative for the factory aux. Attached are the 26 error codes I'm getting.
The two codes codes U0001 and U0401 I feel are two true errors the rest I feel are occuring due to these two above. I'd like to know 1) do you feel this is electrical or powertrain 2) would you proceed to pay the $2000.00? In the event it is deemed to be powertrain then the 2k is waived.

Please let me know your thoughts. And thank you all in advance.

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[ShadowsPapa]

Definitely an electrical/wiring issue. Possibly a bad/loose connection.
This happened AFTER the transmission replacement?
Those are all communications issues, so I suspect a connection problem.
If they are smart they'd start with every connection that they had to take loose to replace the transmission.

 

[RobCart]

@ShadowsPapa it actually started happening at around 25k to 28k. I took it at 37k and they replaced the transmission.

 

[Hootbro]

I think the primary driver is the U0001 CAN C BUS code and everything else is a cascading code to include the U0401.

If you drop and remove the glove box like you are accessing the cabin air filter is two Star CAN connector blocks. The one on the left (green) is your CAN C BUS and the one on the right (white) is your IHS BUS.

With the vehicle off and access to the green CAN C BUS connector block, I would do a visual inspection to see if there is any rubbing, chaffing or other maybe accessory wires running near this connector block. Check and make sure all connectors are fully seated and if necessarily, remove each connector, inspect pins for corrosion and then reinsert back into the connector block and make sure fully seated.

If the visual inspection does not yield anything obvious, then you are going to need someone that can scope the CAN C BUS wave-forms and try to deduce if you have a wire problem (short) and/or another module that is attached to the CAN C BUS is dragging the BUS down.

I will say upfront, probably 75% of the dealerships do not have a tech versed enough to properly troubleshoot a CAN BUS type systems wave-forms with a proper scope meter. They will hunt and peck and shotgun parts before even considering a proper scope based diagnostic. Very easy to waste a lot of money on this type of troubleshoot due to ineptness.

 

[ShadowsPapa]

If you drop and remove the glove box like you are accessing the cabin air filter is two Star CAN connector blocks. The one on the left (green) is your CAN C BUS and the one on the right (white) is your IHS BUS.

I was in the dentist office deciding among crown with root canal, extraction or crown with no root canal and I reminded myself of that connector set back of the glove box - it's a common theme on the Wrangler forums.
Oh, the final decision - dentist says he believes crown with no root canal for now will work. So I have what Captain Kirk and Bones call "numb tongue" for a couple more hours.

Anyway, once again, I could say "as usual" Hootbro is going a good direction. Any communication issue is going to trigger other errors. If there's a general problem with the bus - anything riding that bus can suffer communication drops or errors.
It's a network, I can liken it to a bad Ethernet issue - dropped packets, retries, hit and miss communications. I suspect this is a simple communication where one side doesn't tell the other side try again - if the packet doesn't make it, there's likely no retry, it simply fails and there's an error recorded.

 

[Sandevino]

The CAN BUS C is the problem here. If it were mine, I would start with removing connections, inspecting the connectors, adding dielectric grease and reinstalling.

Have you had any water intrusion into this area?

 

[ShadowsPapa]

The CAN BUS C is the problem here. If it were mine, I would start with removing connections, inspecting the connectors, adding dielectric grease and reinstalling.

Have you had any water intrusion into this area?

Agree - it's a general bus communication error - causing issues with communications riding that bus. Fix the CANBus communication or connectivity issue and the rest should settle down.
The area Hootbro pointed out is a common place of this type of problem.



When looking over the connectors - look for any that have a pin or receiver/socket that appears pushed back in the shell. They should all sit even in the shell.

 

[booneja]

Once again our forum sleuths, are more knowledgeable than our trusted service techs

 

[Sandevino]

When I got into the business in the 90's we were taught to troubleshoot and swap parts as a last resort.

Today... FIRE UP THE PARTS CANNON!!!!!!

 

[ShadowsPapa]

When I got into the business in the 90's we were taught to troubleshoot and swap parts as a last resort.

Today... FIRE UP THE PARTS CANNON!!!!!!

I was called a "natural troubleshooter" by my HS and college teachers. I can't stand tossing parts at something until it works.
After college, the owner of the shop I worked in (this was the late 1970s) threw the tough stuff at me. I walked in looking for a job and his service manager had a Ford on the scope trying to figure out a misfire condition. We chatted a while and then he stood away from the car, and told me if I could tell him what was wrong with that engine he'd consider me. I ran it a bit, checked the scope patterns and told him where to look. A minute or two later he said "you start on Monday".
He was a clean-cut family guy, I was a long-hair.

 

[ChrisNLA]

That stuck out to me as well. The CAN Bus system is mad at something, and one small problem can bring the whole system down.

We build new fire apparatus and CAN Bus is becoming more and more prevalent in those as well. One loose connection or a missing terminating resistor (or one put in the wrong place) and it brings the entire system down.

Edit: Saved this post to remind me there is a block of important junk behind the glove box to check...

 

[Sandevino]

Take a look at your fuses and added electric components. I've seen additional electronics add excessive resistance (or capacitance) bringing circuits outside of spec.

I'm the a-hole that added resisters to circuits in conspicuous locations when teaching techs how to troubleshoot. I doubt the shop is testing circuitry but they are on the right path wanting to remove all extraneous non-factory electrical components.

 

[ShadowsPapa]

Take a look at your fuses and added electric components. I've seen additional electronics add excessive resistance (or capacitance) bringing circuits outside of spec.

When I designed the computer that was to be the interface for the Compressor Controls Corp. Series IV turbo-compressor controller, we were still in the 486 computer age for the most part.
I found through testing that the order of the expansion boards on the main boards of the motherboard mattered. At times in the environmental testing where things were constantly hammered on under harsh conditions and running my scripts to thrash things, the systems failed to restart if each board wasn't in the slot I specified. Generically speaking it shouldn't matter - there were 3 slots, but if the video board wasn't the one in slot 1 next to the power supply, one time out of dozens, it may not POST.
The EEs basically said similar to what you just said - one may change the capacitance or load on a specific part of the bus and the next board didn't get what it expected.

 

[Sandevino]

When I designed the computer that was to be the interface for the Compressor Controls Corp. Series IV turbo-compressor controller, we were still in the 486 computer age for the most part.
I found through testing that the order of the expansion boards on the main boards of the motherboard mattered. At times in the environmental testing where things were constantly hammered on under harsh conditions and running my scripts to thrash things, the systems failed to restart if each board wasn't in the slot I specified. Generically speaking it shouldn't matter - there were 3 slots, but if the video board wasn't the one in slot 1 next to the power supply, one time out of dozens, it may not POST.
The EEs basically said similar to what you just said - one may change the capacitance or load on a specific part of the bus and the next board didn't get what it expected.

I built boards and circuits for 386, 486 and Pentium based systems. Damn... we are truly showing our age.

 

[ShadowsPapa]

I built boards and circuits for 386, 486 and Pentium based systems. Damn... we are truly showing our age.

No kidding. Windows NT, OS2......... our engineers couldn't wait to get their hands on Pentium systems.
I worked with a guy who was taking a break from being professor of computer science at an Iowa college. He told me of his days when HP contacted him to come up with drivers for their latest printer line - oh, we need it next week. He said he stacked Mountain Dew and Snickers bars in his "closet" and stayed all weekend until it was done.
I talked at length one time with a head engineer from YMS - Young Microsystems, then a maker of a very good, reliable and compact 486 board. He talked about the pressures of designing the next system board and how their health coverage was good - and the part used most often was mental health portion when the engineers suffered breakdowns from the stress.

I was also dealing with converting a major international corporate away from thin net/Ethernet to 10BaseT with the head of IT insisting there was nothing wrong with coax Ethernet and no, 10 different coax LANs running to multiple boards in a single server was fine. Each network card supported from 2 to 4 networks. He killed that Netware server because it was so busy routing traffic it couldn't deal with login attempts.

Stressful work - keep up or get left in the dust. I really liked that head of IT - he was my boss and we were basically friends. It was a sad day when I realized I was the reason he was let go.

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