2016 Model S 75D – sudden cascade of MIA alerts, 12V not supported, front motor disabled, limp mode
Recent work: The pyro fuse and the 12V battery were both replaced on 20 Sept 2026, about a month ago. No issues since then until today.
What happened: The car was parked. The moment I got in (not driving), it threw a big cascade of alerts all at the same second (15:47:42) and went into limp mode. Result:
Front motor disabled ("OK to drive")
Reduced power / acceleration and top speed limited
No regen, no traction control, no stability control, no AEB
Charge port disabled / "car cannot charge"
Key alerts (from service mode)
GTW_w405_12VNotSupported
GTW_w157_lowVoltageSupportFault
GTW_w017_accLoadShed / GTW_w018_hvacLoadShed
Lots of MIA alerts: GTW_w083_disMia, GTW_w021_thcMia, GTW_w019_bmsMia, GTW_w023_chgMia, GTW_w042_cpMia, PMS_w039_disMIA, PMS_w040_pmMIA, PMS_w042_gtwMIA, DI_w040_disMIA, EPAS2_d067_diMia
DI_w062_systemLimpMode, DIS_w126_limpMode, BMS_u008_limpMode, BMS_w094
DAS_w009_aebFault, DAS_w053_radcCommIssue, ESP_w002/w003/w007
My theory: It looks like the 12V supply dropped out (DC-DC not supporting 12V?) and everything else is knock-on faults. Since the 12V battery is new, I'm wondering about the DC-DC converter, or whether something wasn't reconnected/seated properly during the pyro fuse job. I don't see any contactor, isolation or pack fuse alerts.
Questions:
Has anyone seen this exact pattern, especially after a pyro fuse replacement?
Could a loose connector or ground from that job cause this a month later?
If it's the DC-DC, any idea of repair cost?
Screenshots attached. Thanks! (Sorry for some pics being in danish)