BMW fault code D688
Telematics control unit
TEL: Fault, phone board sending invalid key code
Module version: Telephone USA (TEL_USA)
In: 7 Series (E65) 2001–2008, 7 Series (E66) 2002–2008, 7 Series (E67) 2002–2008
Reading and clearing it
Fault code D688 is a BMW code, stored in the car's telematics 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 telematics control unit is on: 5 Series (E60), 5 Series (E61), 6 Series (E63), 6 Series (E64), 7 Series (E65), 7 Series (E66), 7 Series (E67), X5 (E70), X6 (E71), X6 (E72), 1 Series (E81), 1 Series (E82), X1 (E84), 1 Series (E87), 1 Series (E88), Z4 (E89), 3 Series (E90), 3 Series (E91), 3 Series (E92), 3 Series (E93)
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