More weird than normal sway bar issue - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 4 Old 03-17-2019, 11:55 AM Thread Starter
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More weird than normal sway bar issue

All,

Been reading up on JK swaybar disconnects when mine developed the usual issues. Took the assembly off, cleaned up and and relubed entire thing, put electronic module in the oven on low temp for a bit to get rid of moisture since it's a sealed until and can't be serviced, put it all back together and it worked but only intermittently. Cleaned up connector as best I could, etc and still marginal at best. Finally gave up on the cheapo connector and soldered the wires from the harness directly to the pins of the disconnect unit.
Now here where things get weird:
The unit now works PEFECTLY every single time when you turn the vehicle on. Disconnects on command, slow blink while disconnecting, sway bar ends become free and light comes on steady. Press again, slow blink, swaybar becomes solid, light goes off.
Issue is that after 1 minute and EXACTLY one minute from turning on the ignition the swaybar light begins to blink fast (indicating fault condition according to fsm excerpts I have seen online) and will not disconnect (if currently disconnected it reconnects). I literally can't IMAGINE what the fault it.
CANbus is working because the light indicates accurately and the system responds to commands.
Plunger that senses position is working because the light is perfectly accurate for first minute (corresponds with actual sway bar condition).
Ignition on wire is working cause it works normally at first.
It's obviously got 12V power/ground.

Anyone have a fsm or some other knowledge that could tell me why I am getting a fault even when everything appears to work?
Again this fault occures after exactly one minute every time without fail.
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post #2 of 4 Old 03-17-2019, 12:48 PM Thread Starter
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Decided what the heck... Wasnt working anyway. Unsoldered all the wires and removed the electronic portion of the assembly. Drilled out the rivets and peeled off the adhesive to find the sorriest looking circuit board I have ever seen that still (kind of) works.

Still curious what the SPECIFIC fault is but make a lot more sense that SOMETHING isn't 100% now.

I tried uploading a pic but the images on my phone are too large. Suffice to say its amazing it works at all... Aside for significant quantities of water still present inside with the logic board there is huge amount of corrosion all over the board and the conformal coating is beginning to fail. Some of the surface mount ICs appear to have been submerged for long enough that their part numbers and stamped data codes are no longer legible.

My instinct tells me its salvageable because it functions partially but we'll see.
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post #3 of 4 Old 03-18-2019, 04:49 AM
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I don't run an electronic disconnect on my JKU but if I did ( & from what I have read over years on this and other resources for our model Jeep )I am pretty sure I'd have that EVO manual disconnect option that you just move to disengage vs. the notoriously faulty factory disconnect electronics.

Lotsa info on this if you limit your Google search to just JKOwners.




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post #4 of 4 Old 03-19-2019, 04:10 AM Thread Starter
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Yeah I thought about just going manual route and had everything been working ok I might have but since its not working I just CAN'T leave it alone... That'd be like losing to the Jeep.

In other news after cleaning up the board as best I could it got worse: Now it won't even establish CANbus communication. I have been though to circuit with a fine tooth comb (and an oscilloscope which was more somewhat more useful than the comb) and poured over the datasheets for every major part on the board but no luck. The main chip (a MC9S12DG128 microcontroller) appears to boot normally, clock looks good and it outputs 5V and 2.5V from its internal regulator to the various drivers and com chip on the board. Unfortunately for whatever reason the CANbus never connects and after 33 seconds it shuts down the 5V and 2.5V outputs and enters a low power standby state. This board has one or more internal layers so I can't see where everything goes and there are a few parts who's PNs came off over time so I am about out of stuff to try with this board.

Plan B is buy a CANbus transceiver off Amazon, interface that with an Arduino Mega which I am in the process of installing in the Jeep and connect it to the Can-C network where the swaybar disconnect went. Others have done something similar so much of the leg work is done... CAN-ID 325 byte 6 represents the swaybar button state so by monitoring this I will know if the button has been pressed, CAN-ID 994 is the dash light so by sending data on that I can control the dash light (not sure which byte but Ill figure it out through trial and error). From there its just a matter of using relays to supply the OEM motor and brake release with power at the desired time and using that little plunger thing that moves with the sway bar engager collar to monitor state using a prox sensor.

Plus my Arduino is interfaced with a 3.5in touchscreen which will mount on the dash in a 3D printed housing which will replace the OEM cell phone tray thingy in the dash so I can add some messages for swaybar state to that and my swaybar will be able to remain disconnected at any speed or even in 2WD... Lots of work but it will be a nice upgrade and it beats spending $1500 on a new assembly only to have the same thing happen again in a few years.
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