might be worth checking the individual wire or connector terminal that goes from the TCM to the PCM isnt failed, as I understand it the TCM controls trans.

a used TCM is cheap, and handy to have though !

 

I think you may be getting closer. There are several different ways you can go from here with the information these codes provided. I would say you can ignore the PCM specific code if you want right now, since you are seeing a reading of 60 Ohms on the BUS. This means both of the termination resistors are working in unison together with each other. If either one, the PCM or the cluster gauges resistors were faulty, you would instead be seeing 120 Ohms. This kind of points to say the PCM is not the problem. The PCM code only means it is unable to communicate. The TCM code is probably being thrown because it may actually be the faulty problem module? This is not always going to be the case, and is unfortunately not a guarantee.

You can probably forget about the door modules for now too.

Before you start, can you try something? Get another BUS voltage reading. Place the voltmeter probes between the #3 and #11 DLC pins each separately, to read the voltage between each of them with the other voltmeter lead going to the DLC pin #5 (DLC #4 or #5 will work for this..) to see what you get?

Here is something else to keep in mind. The cluster gauges module is the final module in the line (aside from the PCM). If you were to go around and disconnect every single module, the BUS (+)/(-) lines should be at 2.5 VOLTS by this point. If the BUS still does not get up to the 2.5 VOLTS reading when you are down to just these two modules? it is very likely it is something in the cluster gauges module causing the problem. It is the last one in the line. I still do not think the cluster gauge module is it though, since you did get a 60 Ohms reading. This indicates both your cluster and PCM are doing okay. So far, you have been systematically ruling out some of the more important modules in that way.

If you haven't? You may want to try pulling to disconnect the TCM module. After you have the TCM removed, start and run your Jeep. The only thing you are looking to see is if the cluster gauges will come back alive when you have the TCM disconnected. If the gauges do come back alive when doing this? It definitely points to the TCM as the only module with a fault. If the gauges do not come back on when you have the TCM disconnected? It does not mean the TCM is okay. But, it does point out for you to possibly be looking for another different faulty module (maybe, as well as the TCM)? Unfortunately, unless you were to unplug all of the rest of the modules first (except for the cluster and PCM), and then were to disconnect the TCM, and then the gauges came alive? Then, this would ultimately be the only actual sure-fire way to know it was only due to having a faulty TCM. Still, it is a worth a try to see if the gauges will come back alive for you with having the TCM disconnected.

With the TCM code your Jeep is showing. You should be following the diagnostic procedure pasted above (ignore the DRBIII reference).

There are actually two things you should do now. Test the wiring between the PCM-C3 connector to the DLC BUS pins #3/#11 to rule out the PCM as the reason (since you do have a PCM specific BUS code). I pasted a diagram of the PCM-C3 connector to see. You want to go between each of the BUS(+) and (-) of the C3 to the BUS(+) and (-) pins at the DLC and see what you get? You should see near full continuity between the two... the BUS(+) of the PCM connector to the BUS(+) of the DLC, and from the BUS(-) of the PCM-C3 connector to the BUS(-) at the DLC. The battery negative terminal/cable needs to be removed and isolated for during the testing. Go from the socket (harness side of the PCM connector) to the DLC pins when getting the readings. You should normally be seeing near full continuity for the readings when doing this test.

Next, you want to test for resistance between the TCM connector going to the PCM C3 harness. It is the same basic procedure used above for testing between the PCM BUS circuits to the DLC. Take the readings by going from the harness side of the TCM connector BUS(+) to the BUS(+) at the PCM-C3 harness connector, and from the BUS(-) of the TCM harness side to the BUS(-) at the PCM harness. The battery negative cable needs to be removed and isolated for these tests. You should normally see less than 5 Ohms between both BUS(+) and the BUS(-) of the TCM harness connector to the the PCM harness. If you see less than 5 Ohms.... it indicates having a bad TCM module as the reason for your Jeeps BUS problem.

 

That's twice now when you and I were both on it at the same time with doing the same things like that....

(edited):
I edited the final paragraph in my post above. In case you read it before I realized and noticed a pretty big mistake? It should be corrected now though.

What was the reading you got?

 

If it was less than 5 Ohms between the PCM harness to the TCM harness? This only rules out the wiring. Disconnecting the TCM should bring things back to normal for you again with the gauges, and for seeing 2.5 VOLTS on the #3 and #11 DLC pins.

You should be able to remove the problem module, and it should make things go back to normal. Then, you should be able to cause the same issues you were having to recur again, by reconnecting the TCM back in one more time as a final verification type of test.

I know the diagnostic manual test procedure goes right to saying the TCM module is bad when you get a reading of less than 5 Ohms. Still, I think you should be able to get rid of, and recreate the problem by way of the TCM module.. by removing and then re-connecting it back up again.

 

I guess maybe I missed your last post from yesterday.. I didn't realize you already tested going from the TCM harness to the PCM-C3 harness.

If I am coming across as being annoying or anything, please let me know? I do not in any way think you actually feel like that towards me, as you are not coming across to me like that or anything. Sometimes, I feel like that about myself though. I have always been one of those people everybody always seems to like. You know how you could get a feeling of knowing something like that (and so I have also always been told). I do not have self esteem issues I promise, and I am not looking for a build-up or for something like any praise. Every once in awhile though.. someone will take offense to me. I think when this happens, maybe it is because the person may be thinking I am a "know it all"? Its so rare though when that happens. So, who knows? In any case, I do not want to come across like that in any way.

I really want you to be able to find the reason why you are having the BUS problem on your Jeep. I am sure not near as much as you. I truly believe you will be able to find the reason.

Sometimes, with the way I understand it.. a bad module is no longer able to communicate any at all. Because of this, it is programmed for a faulty modules neighboring module to do the communications for on the bad modules behalf instead. Having things set-up like this actually makes a lot of sense when you think about it. A similar thing happens when there is a problem elsewhere, and sometimes the PCM will throw say maybe an oxygen sensor code.. when there is not anything specifically wrong at all with any of the oxygen sensors themselves, you know? You end up having to hunt down the problem for why that oxygen sensor code was thrown..

With the TCM BUS communications error code showing up like it is. It could likely be any one of the modules closely associated to it? The SKIM, Airbag, and the Overhead Console modules appear to be in a closely associated form to the TCM module. At least they do from the one diagram. It is complicated though. When you have it narrowed down to showing as having a fault with any one of the specific modules. You then have to find out what is actually specifically going wrong there with and at the module. The module could be perfectly okay having no fault of its own so to speak.. If it is only being effected by a problem that is actually occuring elsewhere to it. Maybe, it could be on one of the modules own specific wires? Or, a sensor with which shares the same circuit as this module. Or, any of the wires on the same circuit which is also being shared by one of the sensors (the shared 5 VOLT wire..?)?

The best case scenario right now - Is if unplugging the TCM module brings the voltage back up to normal on the BUS (+)/(-) circuit wires.. and the gauges light back up to work when you unplug the TCM. Even then, it is still not a guarantee to be the TCM as the problem. It is much more likely if it were to happen like this though. Before you are to fully condemn any module, it is still recommended to test any of the direct wires going to the module as best as is possible for faults in them too.

 

I checked that wire from the PCM to the DLC, from the TCM to the DLC, from the TCM to the PCM, all is good.

Checked the window module wiring and all is good.

Plan of attack unless something else comes up.

Pick up a used PCM at the junkyard, if no change, exchange it for the TCM, if no change, off to a repeatable shop for repairs. My wife asked if this vehicle is worth spending several hundred on and I explained that is is like so. This will be my daughter's vehicle. I have had this vehicle as either the 2nd or 3rd owner, at least since 80k since 07 or 08. I know the ins and outs (other than this issue) and knowing this is a solid vehicle and not knowing what crap you may get on the used market, your dam right its worth fixing. Plus it's a Jeep, that should speak for itself.

 

A quick run down so we are all up to speed, I have checked the wiring from airbag mod to DLC (not sure if I have checked it to PCM), but power, ground, and can bus to DLC are all good

PCM to TCM all good including resistance, which as mentioned from the diagnostic flow chart, points to a bad module. Now, unless the issue with the module is an issue that can create this specific issue. Such as not only the code but the no bus and airbag light, I can't understand how that it is at fault. Hence why we need to unplug the TCM and see what happens. This has been done and no change. As a matter of fact, I have unplugged TCM and airbag mod in different sequences and no change, I even unplugged my cluster and never get 2.5 voltage back.

PCM to DLC good
TCM to DLC good
Airbag to DLC good
PCM to TCM good
PCM to airbag unknown, going to check first today.

My jeep does not have SKIM or overhead with compass modules. But I assume the wiring is there and have to believe that if it is, could it have been damaged robbing me of my 5-volt reference. So it may not be a bad idea to check that out.

I don't like throwing parts at something, but time is running out. I have obligations coming up in the next 2 weeks and this project is starting to consume some time, therefore, I am missing out on opportunity cost. Hence why I mentioned picking up a PCM and giving it a try. Today may be the last day I can make it to the junkyard for a couple of weeks and this thing needs to be running after the first of the year.

Oh yeah and my wife wants to go by a new couch today

 

There is one connector that I would like to check but can not locate it. My luck is that is located behind the dash somewhere I can't reach, knowing my issue, I have to wonder if something isn't wrong here and why I haven't discovered, but this could be a rabbit hole and I would hate to have to pull the dash back out to figure this out. It is the one circled, the yellow c205.

 

For documentation purposed
Unplugged Crank position sensor
Can bus pin 3-300 millivolts
can bus pin 11-10 millivolts

Plugged back in
No difference
Can bus pin 3-300 millivolts
can bus pin 11-10 millivolts

The reason I wanted to check this was for 2 reasons, someone mentioned it in this thread and I remember dropping my wrench in that is when reinstalling one of the heater box nuts.
Also, if I have given any other goofy voltage readings pertaining to can hi and can low, its more than likely due to not having the key fully turned to the run position.

 

I do not think the overhead, compass, or the SKIM pre-wires should be a concern. Even if some of the wiring that is installed for these were exposed, cut open or anything, they do not terminate to complete their circuits anywhere to result in having any type of an effect on the system. It is as if you had them.. you have these modules already removed.

There is one that is different in this regard though. It is the auto headlamps module. Even if your Jeep does not have the auto headlamps option, or this module, the wiring for it is still going to be connected up in such a way to complete the circuit. It has something to do with the laws in Canada which require the headlamps to always be turned on at all times, and the way in which Chrysler set up this part of the system. I doubt it applies for anything to do with your Jeeps problem. It is still interesting..

The C200 series connectors are all used for connecting wires up on the instrument panel harness. I cannot find anything in particular on the C205 connector shown from the picture diagram you posted. It is a two-way connector, and it may lead to the doors from something I just read? Although, I did not read this from off a Jeep specific schematic detail.. Other things I saw have it ultimately going to the headlamps switch. On your Jeep, maybe it is for the blower motor and for the blower motor resistor though?

 

Airbag module
pin 19 can + to pins 3 and 30 on DLC and PCM have continuity with little to no resistance
Pin 18 can - to pins 11 and 28 on DLC and PCM have continuity with little to no resistance

Not sure if Can bus - is supposed to have continuity to ground, but it does.

Dummy me realized what C201 is, however not sure about C205 and C206. I have to wonder if C205 isn't the main connector for the airbags to the airbag module and C206 isn't intended for the SKIMS.

Coming back to this theory, but switch the thought of the TCM with the PCM. This is why I would suspect the PCM if all the wiring test out, as I would have to wonder if it wasn't sending a false reading to the cluster. After all, it would be the one to send or store the codes as the last in the chain....Wouldn't it?

 

True, but what if one was shorted causing the voltage drop? If this would not be the case, then it would bring me back to my last statement on my last post.

 

Have you been able to focus any of your time on grounds? If one of the important grounds is not exactly proper, it may be able to adversely effect the system in such a way to cause one of the modules associated to the TCM to drop out. This would of course most likely be related to one of the other components associated to that other module to cause it to drop out.. It would not necessarily have to result in having any known parts failures, or other running issues either. Most likely it would though.

I think if I was to decide on checking any of the grounds? I would want to look into cleaning and checking out the main ground supply for the PCM. Fortunately, I think there is a single ground supply for both, the PCM and the TCM. I may not have the exact right manual pulled? Fom what I can tell though, it should be the G-101 ground located in the engine compartment.

G-101 should be the main battery to engine, PCM, TCM, TC, and the O2 sensors ground supply. The O2 sensors and their wires are definitely also known to be messing things up somewhere else away from themselves too.

 

Cluster
Can + pin 2 to pins 30 and 3 continuity with little to no resistance
Can - pin 1 to pins 28 and 11 continuity with little to no resistance

 

It couldn't, as it would not be able to without having a completed circuit. Worst they could do would be to have rubbed through themselves exposing their own wires, to have them touch to another wire on a different part of the circuit which also has exposed its wires, to short out somewhere in that circuit. Unless I am way off base.. from what I know that is how I believe it works?

If one of their wires were open? You would already know about it in another way.. if it were to have cut out any of the 5 VOLT supply from out the chain?