BMW fault code A21A
Auxiliary control unit
ZBM: IBS equipment battery, Communication fault
Module version: Two-battery management (ZBM_RR)
In: 7 Series (E67) 2002–2008
Reading and clearing it
Fault code A21A is a BMW code, stored in the car's auxiliary control unit, not a generic OBD2 code (P0xxx): a generic OBD2 reader only reaches the engine's emissions faults, so it won't show it. AutoLingo for BMW reads it with BMW's own diagnostic protocols, in plain English, with the details the module stored about it, and clears it after a repair. If a fault comes right back after it's cleared, the problem is still there.
The auxiliary control unit is on: 7 Series (E65), 7 Series (E66), 7 Series (E67)
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