Description

What this service does The Siemens MSD80 (and later MSD81) DME runs the BMW N54/N54T twin-turbo six. Its signature failure is a persistent misfire that keeps coming back no matter how many coils, plugs or injectors you fit – because the fault is inside the DME, typically a failed MOSFET / injector-driver stage on the board. We repair your own unit at the source with upgraded components and return it ready to bolt straight back in. It stays your original DME, so VIN, mileage and keys are untouched and there’s no coding.

Fits: N54 / N54T – 135i, 1M, 335i/335xi, 535i/535xi, X5 35i, X6 35i, Z4 35i (E82, E88, E90, E91, E92, E93, E60, E70, E71, E89), roughly 2007-2013.

Common symptoms

• Random misfire across one or more cylinders, worse under load
• Misfire codes that return after new coils, plugs or injectors
• Rough running, hesitation, engine light, limp mode
• No communication with the DME (severe cases / after a failed tune)

Common fault codes 30BA / 30BB – DME internal failure; 29CF-29DA – cylinder misfire detection; 2E7C – BSD line fault caused by DME failure.

Fits these part numbers 7575875, 7583332, 7594305, 7586940, 7573863, 7588620 (BMW) – Siemens: 5WK93614, 5WK93628, 5WK93648, 5WK93651, 5WK93642, 5WK93650. Not a complete list – check the number on your DME label.

What to send Just the DME – no CAS or key needed for the misfire/30BA repair, it stays plug-and-play. (A separate CAS-sync fault exists where the DME and CAS lose their sync code; that one needs DME + CAS + key. The misfire repair does not.)