MSD80 Mosfet Repair Service

MSD80 was in early N54 vehicles that had weak MOSFETs from factory, BMW updated their hardware on later models aka MSD81.

Related error messages:

30BA DME digital motor electronics, internal failure
30BB DME digital motor electronics, internal failure

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29CD misfirings, cylinder 1

29CE misfirings, cylinder 2

29CF misfirings, cylinder 3

29D0 misfirings, cylinder 4

29D1 misfirings, cylinder 5

29D2 misfirings, cylinder 6

(if these errors cannot be fixed replacing ignition coil; spark plug; injector).

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2E18 ignition, cylinder 1

2E19 ignition, cylinder 2

2E1A ignition, cylinder 3

2E1B ignition, cylinder 4

2E1C ignition, cylinder 5

2E1D ignition, cylinder 6

For MSD80,  ISL9V5036S3ST IGBT switches were used to manage the ignition coils. The max allowed voltage of Uds is 380V, real-life measurements show – the voltage for ignition switches (in short-term) reaches the max allowed value and the transistor is entered in self-protection mode (with increased heat dissipation, oscillation)!

How BMW allowed this “solution” to go into serial production? It’s not understandable. But one thing is clear – it is only self-explanatory, that these IGBT transistors are getting damaged.

In the picture: real signal oscillogram of MSD80 ignition coil management output. Upeak reaches 350 .. 380V (probe 1:10)

Some images, how does the MSD80 management unit looks like.

In the image: upper part of top PCB: general CPU, power supply, H-bridge drivers (for management of servomotors), 6 pieces of transistors (for ignition coil management), 6 transistors: low-side injector’s switches; a power switches for 12V loads PWM management.

In the image: the bottom part of top PCB: transistor drivers for ignition coils and low-side injectors switches; peripheral MCU, etc. on the left and bottom PCB: high-side management units of injectors (output stages) – on the right.

Output cascades of injectors management.

MOSFET transistors of the injectors management are used (lately replaced with IGBT transistors). Each two or three (of one bank; N43/N53 series engine) transistors have a common current measurement resistor (in green color, in the image below). If even one of the transistors is getting damaged, MSD80 is not able to manage all remaining injectors (of exact bank) and switches off all injectors of an exact bank.

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