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  Topic Review (Newest First)
10-15-2019 03:07 PM
themorganshome BILLWILL and BigJim1,
I need to close this loop and explain what finally fixed my no-BUS error. Finally out of a lot of frustration, I got a second opinion from another jeep dealership. I decided to go to an older one, that hadn't been made all new and glitzy-looking, like a lot of dealerships do of various manufacturers, to be more appealing. I thought I should go somewhere where people have been going to for years despite the not so new look. They decided to reflash my BUS computer system. They put back on the original cluster, and it worked just fine. They believe that the newer dealership had techs that just didn't want to do the hard circuit research to really get down to the bottom of my issue. They made it work. They earned my business forever, and I told them that the glitzy new place failed me and that I never plan to step foot in that place again. I hope this helps. Thank you BILLWILL for doing some sleuthing for me two years ago. As for BigJim, I hope you can find a new BUS computer for your friend's KJ, have it reflashed and installed at a place that will keep trying things until it works. Which dealership #1 wouldn't help me do. They were lame...
10-15-2019 06:07 AM
bigjim1 did you ever find the real problem? buddy is having the same thing.
11-01-2017 06:54 AM
Billwill OK so are you still getting the No Bus Error?

Which flow chart are you following? My copy of the 2002 KJ Service Manual I downloaded years ago for the 2002 KJ from colorada4wheel.com/manuals/Jeep/KJ does not seem to have a description of the CEL codes and flow charts on what to do.

For my 2002 Export CRD I use a different manual for CEL codes which are only relevant to the Diesel models.

I presume you are not driving the Jeep with a code reader plugged in?
10-31-2017 07:12 PM
themorganshome I spoke too soon... I got all excited that possibly all was well after cleaning/replacing every fuse... and then the same issues happened. Either one or two error codes occur:

P1698 and P1686. I've been told that the P1686 isn't the main problem. After looking at the service manual of what to do, and it's flow chart (for p1696), that either i have a short/messed up harness, or I have a bad TCM. (..based upon not being able to clear the codes with a scanner, thus the conclusion from the service manual...).

To me the easy thing would be to get a newly flashed refurbished TCM.... but maybe I need to check every wire coning out of the TCM. Should I check the grounds coming out of it?
10-31-2017 01:32 AM
Billwill I doubt that the 2002 KJ came with tire pressure sensors.

Maybe refit your original cluster if you still have it?

Anyhow at least it looks like dirty fuse connections were your problem.....good news!
10-30-2017 06:34 PM
themorganshome Fingers crossed that it may be fixed...! So the car wasn't staying on.... No Bus code of course, and my neighbor's scanner was giving me two codes... So i did a Bing.com search, using different words to see if I got any other ideas... well, a guy in Idaho, on a diff forum, suggested that ".....
I have seen a radio shorted internally take the BUS down. A really simple way to find the cause is to remove each*fuse one at a time, try to start, and reinstall*fuse*until the message goes away and the vehicle starts.*

Just go to your*fuse*box in vehicle and under hood, remove a*fuse, try to start, and reinstall the*fuse*to it's original location. Repeat until the vehicle will start and run. This is standard practice to isolating the circuit that is causing the BUS to malfunction."
Well I did that, but did one better. Each time I took out a fuse , I notice that ALL of them were gunky/blackish and were oxidized on the metal a bunch,and so I took some really fine sandpaper and scraped them all shiny... and then put them back while doing the above suggestion. As I went along doing this, it started working after I cleaned-up and shined the three fuses that went ti the BCM, the Cluster, and the SKIS. These were fuses in the druvers side door panel. Now, the car is running, and all the warning lights are off, except the low tire pressure light. (This could be because the Jeep dealer guy insisted I get a cluster from a 2004 KJ instead of a 2002. I don't know if my 2002 even has a tire pressure sensor....) Anyways, I'm holding my breath, and we'll see what happens tomorrow... If the cold weather or a cold engine makes any difference since I got this working on a bright fall of Sunny day...) All fingers are crossed....
10-30-2017 04:34 PM
themorganshome Update: My neighbor has a code reader and 2 codes are listed: P1698 & P1686. I'm guessing the second code P1686 has to do with starting and turning back off, as if i don't have the correct key FOB.... Any thoughts anyone?
10-30-2017 11:08 AM
themorganshome On visit 1 to the dealership), They simply only came back that I had a bad cluster to start. So I went out and got a "newer one" that had only 100,000 miles on it and plugged that one in (yes, I have this funky sticker affidavit now on the inside of the door panel stating when the mileage change...). The newer cluster immediately had the low tire pressure light turn on, although all 4 tires pressures were just fine. The cruise control also didn't work. 19 miles later... I hear a chime and suddenly the airbag light turns on. 5 miles after that, another chime sounds, all the warning lights pop on and the gauges stop working. We parked the car at her house.... a couple hours later we turn the car back on in a won't stay on after 5 seconds

We have it towed to the dealership. (Visit #2). The guy eventually tells me that their data is showing the pcm is toast I need a new refurbished 1. I went out and got 1 and they installed it. The rest of the story is listed earlier in this thread.

What is (amusing/not amusing) now, is that based upon it being cold or warm outside, or the dew point, or who knows what... it will either start and run with various warning lights on, or it turns on for 5 seconds and gives us the no bus code.

I'm sorry I've been so detailed and long winded in all of this,... I wanted to give every symptom happening in case someone has an "ah-ha" moment, and has a great suggestion for something I should try. I will be trying all of your suggestions this week and I appreciate any help anyone has/will provide. I really mean that. pI don't mind working on cars, but it's not my forte..., it something more I try to save some money with, with here and there. But when it comes to electic issues, it's very frustrating...and we find it ironic it's Halloween time. My 16 year old daughter thinks the car is now possessed because it's random symptoms change from day-to-day almost.
10-30-2017 07:14 AM
Billwill Check page 8Wa-18-1 in the wiring diagrams....shows where the PCI bus goes.

Also shows that Fuse #33 on the interior fuse panel is involved....check and re-plug that fuse.

I agree with jtect here....did the Jeep Dealership find anything with their scanner?
10-30-2017 06:59 AM
jtec long posts get confusing - just old age I guess.

thoughts
If the air bag light is ON - need to read the code.
If the CEL is on or has been on also read code.

I wonder what jeep found as to which item is not on BUS during no bus indication.

Right now I am thinking a power problem, a ign switch or replay not feeding all modules.
10-30-2017 05:02 AM
Billwill Yes this is a very difficult problem to try find....you may end up replacing virtually all the modules in the Jeep at great expense while somewhere the Bus wire is intermittently chafing through to chassis/engine!

A good Auto Electrician may be able to trace the fault if you give him a copy of the wiring diagrams but that may take a long time/expense.

A bad grounding point on the chassis can also cause weird problems....an old Jeep like yours and mine....escpecially if you are in a snow/salt road area can have major damage to the grounding points.

The wiring diagrams has a section where all the Grounding points are identified...most times with pictures. So if you are not getting anywhere check these grounding points out!

Start with the main grounding points of negative battery lead to chassis and the grounding points...two for the 3.7 L...grounding the engine heads to chassis.
Also check the battery terminals and your battery...low voltage to any of the modules causes weird problems.

I will go through the wiring diagram for your jeep and try to list all points where the Bus goes to....then you can try disconnecting all the points and with a cheap Digital Multi meter start doing some measuring for continuity/shorting of the PCI Bus circuit....may include cutting some wires, measuring then soldering them back together.
10-29-2017 10:03 PM
themorganshome Thanks BillWill For all your suggestions. I certainly will be doing lots of sleuthing this week with your guidance including most likely replacing the BCM.

As another update... this afternoon after church, I had my daughter sit inside her KJ and tried turning it on, and it went back to the whole "turn on for 5 seconds and then turn off with a no bus error." It's almost like daily, depending on what the temperature is outside, or the dew point, or who knows what.... it can't decide if it wants to:
1) Stay turned on without the no bus error (but with the Airbag/Low
Tire Pressure/check engine lights on), Or...

2)Flat-out not run longer than 5 seconds (..it then turns off) with the No Bus error showing, (...And every gauge not working and, warning light lit up like a Christmas tree.

A further observation: The other night with the "newer cluster in," after I locked that door... the little red light on the dash would flash as if there's some sort of anti theft warning device installed. Now that light isn't happening at all either... both last night when we didn't have a bus error, or tonight, when we do have the bus error. (It may be nothing, but at least I wanted to share such.)

Ok, so I'll keep you posted. Over these next 5 days, I'll be sleuthing and trying anything. If you have any other inspiration, or anyone does, please reply and offer suggestions because I really want don't wanna go out and buy another car because this one is esentially not working for us.
10-29-2017 02:43 AM
Billwill If you look at the wiring diagram page 8Wa-43-2 you will see that the airbag control module does have the PCI bus going into it....a Yellow/Violet/Orange wire....so it is probably again related to a problem on the PCI bus. I think that this PCI bus will probably be the same wire colors throughout the vehicle...maybe changing to the single wire with a sheaf around it as it enters the PCM....this is what I have seen on my 2002 Export CRD.

Have a look at the diagnostic port where a scanner would plug in....same wire should be present there and so on for all the other components served by this bus.

The only way I could think of diagnosing the problem....other than replacing the BCM module...is to find every point where this PCI wire plugs into and with the battery disconnected...measure continuity from point to point of this wire and then with every known PCI connector pulled out...check that there is no short between this wire and chassis....the cable could be fraying to chassis somewhere.....a lot of work!

The trouble with the wire harness on the KJ is that they do not connect components together by the shortest possible route.....the main harness goes all the way around the engine bay like the Beltway in Washington. To connect components located 18 inches from each other the harness travels around the engine bay for about 8 feet....going through some connectors along the way. This harness travels under the radiator through a metal channel...at least it does so on the CRD...not sure about the 3.7 Gasser!

After a front-right collision with my Jeep in 2007 I had to trace 7 faulty wires that got damaged inside this metal channel up front. Only way to diagnose these was to disconnect every component on a particular line.....including splices...and then measure the suspect wire for a short or semi-short to chassis when it should be floating in thin air! Then I had to cut off the ends of this wire...including splices and replace the complete circuit with brand new wires....taking the shortest route.....the seventh wire that I traced was only done about three weeks ago!

Fortunately I am a qualified Electrical Engineer with many years experience in Mainframe Computers and Robotics so I could do this... retired but still able to diagnose problems.

I would first try replacing the BCM before trying the above procedures!
10-28-2017 07:47 PM
themorganshome Update: We went just now to the high school to have it towed back to our house, but my wife popped in the key, it started and stayed on, and it didn't give us the "No Bus" error, and the gauges worked.. but there are other things going on.
1) check engine light stayed on.
2) low tire pressure stayed on.
3) airbag light popped back on.

So we drove it home since it was running.

A symptom: Within a few days of us purchasing it in April, the airbag light would come on and off randomly almost on a daily basis. Eventually, the Airbag light would not turn off and then the no bus issues started haunting us 3 weeks ago.

In answer to the most recent uestions:
1) Is the vehicle stock? Well...we did the carfax, and it listed a new engine somewhere before 50,000 miles because of an auto accident. Technically the car is at 200,000.
2) Recent major work ?: Yes, I had a non-dealer replace the head gasket in July via a warranty. Airbag light was going off and on both before and after that new head gasket. It ran well (despite the airbag light) all of August and September, then October and the No Bus errors started happening.
3) The dealership that wasn't very helpful was an actual Jeep dealership. The reason being was since the car is 15 years old , you can almost not find a brand new cluster or a new PCM out there, unless they're used or refurbished. They didn't want to spend hours going through all the electric possibilities, given that it's a mystery... (They felt it would be financially irresponsible of them to me) and they also hoped that my problems would be fixed by inserting a referbished PCM. Honestly I'm kind of glad I have the car back because I don't mind spending the hours going through the electrical thingd that have been suggested already....however I will take suggestions from anyone. Money doesn't grow on trees... so come Monday, I start going back at it.
10-28-2017 02:44 PM
jtec questions - maybe a clue.

vehicle is STOCK?
Any recent work repairs maintenance?
The dealer you mention is a jeep dealer?
any issue before headgasket?
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