BMW fault code 0040
Multiple Restraint System
In the multiple restraint system, code 0040 means different things depending on the version of the module in the car. Find your car below; the app shows the right one for yours.
MRS: Coupling in firing circuit, seat belt tensioner, rear left
Module version: Multiple Restraint System (MRS4)
In: 3 Series (E36) 1990–2000, 3 Series (E46) 1998–2006, 5 Series (E39) 1998–2003, X5 (E53) 1999–2006, Z8 (E52) 2000–2003
MRS: Knee airbag, driver (spare)
Module version: Multiple Restraint System (MRS5K)
In: X3 (E83) 2003–2010
Reading and clearing it
Fault code 0040 is a BMW code, stored in the car's multiple restraint system, 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 multiple restraint system is on: 3 Series (E30), Z1 (E30/Z1), 8 Series (E31), 7 Series (E32), 5 Series (E34), 3 Series (E36), Z3 (E36/7), 7 Series (E38), 5 Series (E39), 3 Series (E46), Z8 (E52), X5 (E53), X3 (E83)
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