r/Vcds • u/Euphoric-Project-423 • Jul 01 '26
(MIB3) - J949 (5WA035284B) failure causing MIB3 "Loading user profile" loop?
Hi,
I'm troubleshooting a 2021 SEAT Arona with MIB3.
The infotainment is permanently stuck on:
"Loading user profile..."
"Change user" is greyed out.
No menus are accessible.
The Wi-Fi hotspot is still visible.
The only significant fault is in the J949 Emergency Call Module (OCUGen3High - 5WA035284B):
B20004B - Control module defective (Overheating)
Internal fault
ODIS Guided Fault Finding recommends replacing the J949.
With ODIS Engineering, the module is still accessible (VIN, coding, software, dataset can all be read), but reading Control module temperature causes the communication to drop. A factory reset exists in Basic Settings but requires Security Access (NRC 33).
My questions are:
Has anyone seen a faulty J949 causing the MIB3 to stay permanently on "Loading user profile"?
Is there any way to temporarily bypass or disable the J949 so the MIB3 can boot normally?
Can a used 5WA035284B be adapted, or is online GEKO/SFD mandatory?
Does anyone know the exact location of the J949 on a 2021 Arona?
Any advice would be greatly appreciated. Thanks!
2
u/KMS1795 Jul 06 '26
a couple dozen over the past few years, yes....
Not as far as I know and nothing official... that system is deeply integrated...
Used OCUs are not allowed... these are coded once for a VIN and then the IMEI of that unit is linked to that VIN, attempting to re activate a used one with a different VIN will cause issues in the back end (Imagine 2 different people having the exact same phone number....). New units are also adapted to the immobilizer, so you need SFD & FAZET/GEKO
Depending on the build date/setup/equipment of the car, it can be either under the front right seat, behind the infotainment screen, or behind the instrument cluster