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David Gieswein
David Gieswein,
Category: Jeep
Satisfied Customers: 50
Experience:  Automotive technician at Doug Gray Dodge/Chrysler/Jeep
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P1687 on 01 GCL. No cluster info but all other BCM equipment

Customer Question

p1687 on 01 GCL. No cluster info but all other BCM equipment work. Replace BCM, did not fix, replaced cluster, did not fix, no break in wire from Bcm to cluster, ground connection good, voltage to BCM good, still no cluster info.
Submitted: 4 months ago.
Category: Jeep
Expert:  David Gieswein replied 4 months ago.

Hello my name is ***** ***** I can assist you. Could you please specify if this jeep is a limited or Laredo?

Customer: replied 4 months ago.
Expert:  David Gieswein replied 4 months ago.

Hey there, I have researched this issue and found a few issues with broken wires in the door jam. Apparently there are some bus/comm wires that go through that harness. If they get broken and then short to ground, it can take the whole bus down. Please check the driver side door jam wires. Just find the flexible boot in the door jam and pull it back on either end whichever one is easiest. Then look at each wire carefully.

Expert:  David Gieswein replied 4 months ago.

Can you communicate with other modules?

Expert:  David Gieswein replied 4 months ago.

If the wires in the door are good and you can't comm with other modules, your bus is probably shorted to ground. You will need to access the diagnostic junction port at the bottom of the steering column(NOT THE DLC). It is a 8 pin connector. Once you found it, there may be a cover of some kind to access it. Once you can access the connections(which are all yellow with diff stripes), measure the voltage on any of them. They are all connected. If one is shorted, they all will be shorted, thus, if you remove one of the pins at a time the bus will eventually come back online. It is highly unlikely more than one bus wire is shorted. So just do one at a time them plug it back in. To pinpoint, you simply tell me what the wire color of the shorted bus wire is and I will tell you what module is shorted. If you don't understand and need more help, just ask.

Expert:  David Gieswein replied 4 months ago.

I am signing off for tonight. Let me know if you need anymore help.

Customer: replied 4 months ago.
I can communicate with all modules, i.e windows work, a/c works, door locks work, horn, and headlights work, I don't have cluster info. I have unplugged both door modules still no cluster. I can not seem to locate column plug. Still trying to track it down.
Customer: replied 4 months ago.
Found diagnostic port. Check resistance to BCM 6.5 ohms, check to L door mod 5.7 ohms, R door 2.8 ohms. Just thought about something while looking at diagram plug 2 comes from a few modules. when disconnecting it (#2 yel/vio/gray) cluster came on momentarily then went off. We lost braking ability just before p1687 and p1686(which clears and only comes on after start try). Could the ABS system module be indicating lose of fluid pressure which in turn creates a pci bus failure.
Expert:  David Gieswein replied 4 months ago.

Unplug the ABS module. It could have an internal failure.

Expert:  David Gieswein replied 4 months ago.

Sorry I haven't replied in awhile. I just started a new job at a Nissan dealership today. Also, for some reason didn't notify me of your last reply.

It sounds like you are getting close to isolating the source of the problem.

Expert:  David Gieswein replied 4 months ago.

From the wiring diagram I have, the yellow/violet/gray wire goes to the following:

1. ABS module

2. Driver door module

3. Seat module (power seats, under the seat)

4. Vehicle information center

This is how a bus works......Many different modules have to send information to each other. That being said, the need a telephone line. This telephone line is the bus. If you have let say, you have two modules talking to each other and while they are talking to one another a module comes on the line and just starts blaring all kinds of random words and not making sense. This is what is most commonly referred to ask corruption. There could be a module that is corrupting the bus messages. Which in turn is causing the MIC or the instrument cluster not to wake up. You can try and open and close the doors to wake it up, but if it sees corruption it will go back to sleep. I hope this helps. Keep me informed of your progress and don't give up. I love these kinda problems cause once you have figured it out, your electrical diagnosis confidence level will increase!

Customer: replied 4 months ago.
Sorry it has taken so long, but trying to troubleshoot the modules has turned up no change even after trying to duplicate gauge function after removing ABS module from circuit still no gauge function at any module test. I have only 7 wires at diagnostic plug, 1, 2, 4, 5, 6, 8, & 9. Before when i plugged all but #2 the gauge worked. Now when I do the same test no gauge function. I've disconnected the battery for 15 to 20 min with no change. Very frustrated !!!!!!
Expert:  David Gieswein replied 4 months ago.

Sounds like you have a bear. Give me more time to research this. I am going to find my bus diagnostic books and dust them off. There are some test you can do to measure bus voltages. I just need to find them. Be patient, this is a master level repair. I assure you will find the culprit. I actually went to the training classes at Chrysler for these kind of problems. I want you to think if you have put any self tapping screws anywhere in the frame too. Sometimes they can hit a bus wire causing an intermittent issue.

Expert:  David Gieswein replied 4 months ago.

Ok, here are some documents you need to print out if you can. They are straight from the Chrysler body electrical part 1 class I took. These documents are not for sale anywhere and you can only get them through Chrysler! In other words, the information is Golden info! Print and retain! What you could do is disconnect each module bus wire at the junction port and read the resistance to ground like I think you did before. That will give you each module's termination resistance and then you can compare it to the chart I sent you on document #3. Hope this helps!

Customer: replied 4 months ago.
Printed all will keep you updated, have to work today, so it will take me a little while to troubleshoot.
Expert:  David Gieswein replied 4 months ago.

Gotta work too. thanks for the update

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