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I got itchy and decided my 9 years old wiring also deserve some test as reference for future troubleshooting.
For wiring schematic of M276.9 3.5NA and M276.820 3.0TT , you can get it here : https://mbworld.org/forums/e-class-w...m-harness.html
The test result as follows :
NOTE : I use either +12V positive power injection or -12V negative power injection, depending on what the wire actually carry in real life use. This is safer.
When my special extraction tools and lots of spare SLK 2.8 female terminals arrive in like a month, I will replace this -12V power dumb-azz 0.5mm wire to equal its +12V power counter part of the pin #3 of COP which is 1.5mm.
NOTE : This dumb-azz 0.5mm wire for Pin #1 instead of 1.5mm is only on my M276.820 3.0TT . On M276.9 3.5NA it is the proper 1.5mm size.
I think the electrical designer made the 0.5mm wire size decision after Germany Oktoberfest , the crazy beer drinking festival
See, Pin #2 wire of 1.5mm for W11 the noise control ground, granted its total wire run length is shorter than Pin #1 of 0.5mm , the voltage drop should be this way, not crazy high like Pin #1.
Lug or eyelet wire set of W16/5 un-hooked is per photo below , basically it is not connected to car metal body as it should.
My definition of Battery negative clamp, as below :
I do not test using the car battery, but I use a very controllable power supply instead, like a bench power supply some people call it. It is for better safety as I can limit the current to as low as 100 milliamps or less and voltage
will be very stable to 0.01 volt drift. Car battery if I wire wrong will fry any cable size used on ECM, guaranteed 100% as it can give easy 850 amps burst...KABOOM !!
My eyes working on ECM super small pins are not the best, often I poked or count wrong "hole" hahahaha.
NOW THE INJECTORS
I use -12V negative power injection for these wires.
The wiring for injectors 1, 2 and 3 at Bank 1 ( Right Side ) will be problematic in the future.
It is from loose grip/bite of the female MLK 1.2 terminals at the ECM wire harness side and some also from the injector connector side. Both are female MLK 1.2.
I will address this within this year.
This is a short video of the said "loose" bite of the female MLK 1.2 terminals.
Insulation test is using Fluke 1587 FC.
See video below of what is an insulation test and what it can do as preventive watch dog for injectors wire because it can go up to 200 volts and engine bay temperature on mine can be up to 96C.
One of the important power supply of the ECM logic board, its +12V from fuse 25 and -12V/ground which is from W16/5.
Front SAM ( fuse box ) does offer higher resistance path. The fuse grip and how the copper trace size and extra connectors, extra wire length all create resistance.
Wire length I don't worry much if size is decent , connectors I worry more because of the female terminals...which is always the weak link.
Closer view of the shiny metal and how it bites a fuse or a relay, based on Rear SAM and not front SAM, but same design.
All the 5 the fuses for my engine's ECM : ( a lot is very similar for M276.9 3.5NA )
Fuse 27 is more like keep alive memory kinda power source.
Fuse 22, 23 and 24 does not go to ECM, but directly feeding to components supporting ECM function.
Fuse 25 is the one connected direct to ECM.
06-15-2023, 11:40 AM
. On M276.9 3.5NA it is the proper 1.5mm size.
