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Discussion Starter · #1 ·
I’m trying to unlock a UQ4 MyLink radio in my ‘13. After spending hours and hours trying to communicate with the radio, I believe I have a problem with my low-speed LAN bus. My diagnostic tools seem to be able to connect to the major systems (ECM, EBCM, TCM) but have trouble talking to small items like the radio, instrument panel, etc. I get this message:


I’ve double checked the DLC and the pins and wires are fine. This vehicle seems to be 100% stock. Again, the high-speed LAN modules seem to talk to my VXDIAG Nano and also my Tech2 just fine.

Any thoughts of where to begin? I’m seriously considering just buying the OE radio connectors from Mouser.com and just making my own programming harness. I did reinstall the old OE radio and I cannot talk to that either; I can’t even pull a module ID from it without getting that communications error.
 

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Discussion Starter · #2 · (Edited)
Very interesting write-up here regarding the later Gen Impala’s:


Granted mine is an earlier generation, I might actually try to scope the low-speed LAN bus and see if anything is awry like the linked story had. Don’t ours have those side impact sensors too?

edit
This guy sums it up well on how to find the faulty module (similar to the article I link above) by finding the splice where all of the low-speed GMLAN bus wires meet and then jumping them one by one until the shorted one causes a fault.


I found this in the service manual. It shows that JX205 is what I need to find to isolate the problem.



 

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Discussion Starter · #3 ·
Interesting progression; I did easily find JX205. No corrosion found on the splice plug. I individually tested each module tied into the low-speed data network. I found zero anomalies.





Stupid me - I never thought a about ruling out a bad VXDIAG Nano GM device using my Tech2 to try to communicate with the modules. It talked to the radio just fine.

Fast forward to this morning, I did also buy a VXDIAG SE along with a GM license. Just as I now suspected, the Nano device was defective - it will only talk to the high-speed network. The SE worked perfectly fine. Radio unlocked without difficulty (use Tech2win and configure as a 2006 Monte Carlo LTZ to access the Radio’s VIN relearn menu).





After a restart the radio works great!
 
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