BMW fault code 4B20
Diesel electronics slave
4B20 Electric fan
Module versions: Diesel electronics slave (D51SM670), Diesel electronics slave (D63SM670)
Which BMWs have these versions depends on the engine and equipment, so we don't list them here; AutoLingo for BMW reads which version your car has.
Reading and clearing it
Fault code 4B20 is a BMW code, stored in the car's diesel electronics slave, 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 diesel electronics slave is on: 7 Series (E65), 7 Series (E66), 7 Series (E67)
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