No bus help

[hear]

I believe the skim doesn't stop it from starting, it will allow it to start for "a moment" and then shut'r down if it fails some skim test. The FSM probably explains this in more detail, I don't have a skim'nabled TJ.

For the no crank, I would double check that your clutch safety is engaging/working/still wired up. That will stop it from cranking and is probably part of that remote start system you took out. I don't even know how those work on a manual, I guess you have to be in neutral? But all that wiring is right in that area, I would look there.

 

[sab]

The Bus messages of b0, b1 and b8 and the gauges not moving make me think the issue is somewhere in the wiring or pcm.

Did you find those error message descriptions in the FSM? If not, they are on page 8J-13, and here is a screen shot:

Since you have all of those error messages, the MIC is apparently not communicating with the PCM, the SKIM, the ACM, or the MFS, but the MIC itself seems to be working, since the test is working. I'd suspect a wiring problem (or the MIC comms don't work, meaning the MIC has failed). I'd suggest looking through section 8W-18 and 8W-40 and then confirming connections. Something is preventing the MIC from communicating with everything else...

 

[Daryl]

View attachment 425566

Those are a guillotine style tap. Simply unplugging them could have cut the last strand of wire under the insulation. I would remove each one and give a tug on the insulation. If the insulation stretches you’ll know the wire is broken.

 

[sab]

And adding to what Daryl just posted, if any of those wires have anything to do with the MIC comms, that would be the problem!

 

[jonesnoahr]

Those are a guillotine style tap. Simply unplugging them could have cut the last strand of wire under the insulation. I would remove each one and give a tug on the insulation. If the insulation stretches you’ll know the wire is broken.

Had to run out for supplies, I'll double check that when I get back

 

[jonesnoahr]

Did you find those error message descriptions in the FSM? If not, they are on page 8J-13, and here is a screen shot:

View attachment 425573

Since you have all of those error messages, the MIC is apparently not communicating with the PCM, the SKIM, the ACM, or the MFS, but the MIC itself seems to be working, since the test is working. I'd suspect a wiring problem (or the MIC comms don't work, meaning the MIC has failed). I'd suggest looking through section 8W-18 and 8W-40 and then confirming connections. Something is preventing the MIC from communicating with everything else...

define MIC

 

[jonesnoahr]

Those are a guillotine style tap. Simply unplugging them could have cut the last strand of wire under the insulation. I would remove each one and give a tug on the insulation. If the insulation stretches you’ll know the wire is broken.

all wires with taps are intact as confirmed by tugging and then testing with multimeter

 

[sab]

define MIC

Mechanical Instrument Cluster, which is a bit misleading, as it's as much electrical as it is mechanical...

 

[jonesnoahr]

Mechanical Instrument Cluster, which is a bit misleading, as it's as much electrical as it is mechanical...

Perhaps I will try to swap the mic with a buddy and see if that helps. As of right now I have absolutely no idea. The obd scanner won't connect but does power up. I checked all grounds and they're good. No wires are cut or disconnected. Pcm is getting power and ground. 5v supply is good. Dlc has proper ground and all the Sci and pci have some amount of volatage. Same deal on the pcm connectors. Everything looks fine according to my multimeter.... guess it's dealer time if the mic swap doesn't do it

 

[jonesnoahr]

Perhaps I will try to swap the mic with a buddy and see if that helps. As of right now I have absolutely no idea. The obd scanner won't connect but does power up. I checked all grounds and they're good. No wires are cut or disconnected. Pcm is getting power and ground. 5v supply is good. Dlc has proper ground and all the Sci and pci have some amount of volatage. Same deal on the pcm connectors. Everything looks fine according to my multimeter.... guess it's dealer time if the mic swap doesn't do it

Will the drb3 tool even be useful at the dealer if the obd2 scanner won't connect?

 

[sab]

Will the drb3 tool even be useful at the dealer if the obd2 scanner won't connect?

Probably not. Again, I suspect you have a wiring issue with the bus comms on your TJ, and delving into the wiring diagrams is where I'd start.

 

[jonesnoahr]

Probably not. Again, I suspect you have a wiring issue with the bus comms on your TJ, and delving into the wiring diagrams is where I'd start.

I've looked through about 40 pages of electrical diagrams and pin out diagrams in the FSM. everything labeled as 12+ is good, grounds are good, and 5+ supplies are good. What else do I need to check? I don't have an oscilloscope to monitor Sci or pci wires but my digital multimeter will pulse voltage on all bus lines. I'm not sure what else to check. Any ideas?

 

[jonesnoahr]

One more detail to add. Last night while checking more circuits I unplugged the black harness from the back of the mic and got a no bus message. When I plugged it back in the message went away. Not sure if that's helpful at all

 

[jonesnoahr]

Probably not. Again, I suspect you have a wiring issue with the bus comms on your TJ, and delving into the wiring diagrams is where I'd start.

Should the wires labeled as Sci or pci have a specific voltage range I can see on a multimeter?

 

[sab]

I've looked through about 40 pages of electrical diagrams and pin out diagrams in the FSM. everything labeled as 12+ is good, grounds are good, and 5+ supplies are good. What else do I need to check? I don't have an oscilloscope to monitor Sci or pci wires but my digital multimeter will pulse voltage on all bus lines. I'm not sure what else to check. Any ideas?

You're not checking the comms lines if you're concentrating on 12V, 5V, and ground wires. The comms lines have nothing to do with those. Comms lines are how all the modules talk to each other. Since your code reader won't communicate either, I'd start at the data link connector (the connector your reader plugs into). The pinout for it is on page 8W-80-25. Follow each one of those through the wiring diagrams and pin everything out (by that, I mean check continuity with an ohmmeter from one connector to another.) If you don't know how to check continuity, let me know. I don't know what your skill level is, so please take no offense if you know how to do that. Likewise, if you don't, just ask. Lots of folks here are happy to help. Then look at the pinouts for the two connectors on the MIC on page 8W-80-33. Pinout all the pins that handle the MIC's communication with other modules, which are pins 8 and 10 on C1 and pin 12 on C2. If everything checks out, it may be the PCM. For that, I'd contact Mark at WranglerFix. He and his team know TJ PCMs better than anyone - even Jeep. He's here on the forum as username "wranglerfix."

Finally, you're a new user here. Please don't be "that guy" and abandon this thread. We all learn more about our beloved TJs when users follow up and let the forum (and future people search it) know what solved their problem. When you finally solve this problem, please come back and post what your solution was.

 

[sab]

Should the wires labeled as Sci or pci have a specific voltage range I can see on a multimeter?

You replied while I was typing my response. No, you won't be able to check comms by voltage. Continuity is the best way, as noted above.

 

[Daryl]

Finally, you're a new user here. Please don't be "that guy" and abandon this thread. We all learn more about our beloved TJs when users follow up and let the forum (and future people search it) know what solved their problem. When you finally solve this problem, please come back and post what your solution was.

This ⬆️

 

[jonesnoahr]

You're not checking the comms lines if you're concentrating on 12V, 5V, and ground wires. The comms lines have nothing to do with those. Comms lines are how all the modules talk to each other. Since your code reader won't communicate either, I'd start at the data link connector (the connector your reader plugs into). The pinout for it is on page 8W-80-25. Follow each one of those through the wiring diagrams and pin everything out (by that, I mean check continuity with an ohmmeter from one connector to another.) If you don't know how to check continuity, let me know. I don't know what your skill level is, so please take no offense if you know how to do that. Likewise, if you don't, just ask. Lots of folks here are happy to help. Then look at the pinouts for the two connectors on the MIC on page 8W-80-33. Pinout all the pins that handle the MIC's communication with other modules, which are pins 8 and 10 on C1 and pin 12 on C2. If everything checks out, it may be the PCM. For that, I'd contact Mark at WranglerFix. He and his team know TJ PCMs better than anyone - even Jeep. He's here on the forum as username "wranglerfix."

Finally, you're a new user here. Please don't be "that guy" and abandon this thread. We all learn more about our beloved TJs when users follow up and let the forum (and future people search it) know what solved their problem. When you finally solve this problem, please come back and post what your solution was.

Will do. You (and others) have been very helpful so far! Thank you! I'll be traveling this weekend (originally planned to be camping trip in the tj....) so I may not have a response for a while. But I'll check continuity on a couple when I get home tonight before I leave. I'll definitely keep you guys updated

 

[jonesnoahr]

No solution yet. Everything between dlc and instruments clusters is good. I'll move to dlc to harness connectors next then connectors to pcm. If I have a pcm wire that looks suspicious can I splice a new section of wire in with a crimp connector or is there a special way the pci wires need to be handled?

 

[sab]

...can I splice a new section of wire in with a crimp connector or is there a special way the pci wires need to be handled?

I don't think there are any shielded or twisted-pair conductors in a TJ harness. That's the only thing I can think of that would need special consideration. Maybe someone else with more TJ-specific wiring experience will come along and share more info.