B8.5 No AC after adding Radar mirror tap

[purp13p4nd4]

As the title states. Added a mirrortap power cord, unplugged the wire harness on the mirror temporarily. After plugging back in, the mirrors compass was not displaying and the green indicator light was off. Tried holding the power button and nothing happened. Removed the mirrortap power cord and still nothing. Noticed the AC system also stopped working, blower working.

Checked all the fuses and they are all okay. Scanned for codes and got a couple faults.

00457 Control Module for Network (J519) - sporadic 013-Check DTC Memory
00256 A/C Pressure Temperature Sensor (G395) - sporadic 008-Implausible Signal
01592 Air Quality Sensor (G238) - sporadic 004-No Signal/Communication
00457 Control Module for Network (J519) - sporadic 004-No Signal/Communication


Now its possible that its just a coincidence that the A/C decided to not work while this happened. I am just hoping that someone else might have had these issues and can help me troubleshoot it in the right direction. Thanks!

[Smac770]

It does seem unrelated that the LIN bus line on the J519 for the G395 and G238 messed up after doing that work. G395 issues are not uncommon.

But something is definitely messed up with the power to the rearview mirror. The compass function is completely independent of anything, it just needs power.

[purp13p4nd4]

I replaced the pressure senson/switch and that did not solve the problem. I believe the issue is with the electrical. J519 seems to be responsible for managing the electrical signals. If anyone has any advice for working on the J519 please let me know. I found some other relevant threads on Ross-Tech similar codes and AC not working as well.

If I can't figure this out I may have to call a local shop or the dealership to see if they can fix this issue.

[purp13p4nd4]

Opened up the drivers side dash to access the J519 module. Did not find any clear corrosion or component failure. I guess its alright because I would have to take it to the dealer to be reprogrammed if I replaced it.

Update - Issue Resolved

Turns out the continuity reading on fuse 3 on A for the left cockpit was wrong and actually blew. I feel like an idiot, but I hope this thread helps someone in the future. It should have been obvious since fuse 3 is labeled "A/C system pressure sensor, electromechanical parking brake, HomeLink, automatic dimming interior rear view mirror, air quality/outside air sensor, ESC button"

[Smac770]

Ah, had forgotten that fuse powers multiple devices. Glad it was an easy fix, even if the road to it was not.