Hi all,

Firstly I never know whether to post in the SL AMG board, the R230 board or the M275 board. I guess this is an M275 question but there seems to be a bit more activity here...

Car: 2005 SL65

A while ago I had misfires on 7-12. Replaced the ignition module with a rebuilt one from Clark and all was well for a short while. Then they came back, on the same bank. So I just replaced all the plugs with OEM NGK's and both coilpacks with rebuilt units from Clark.

Misfires remain on 7-12 :-(

I performed some voltage checking per instructions in DAS . The power to the coilpack seems fine - all these tests performed okay:



I then went on to test the input power and grounds at the ignition module per these tests:



11 > 5 reads good, however 14 > 4 reads 0V

If you say "NO" to "are the measurement values OK?" the possible causes/fixes are listed as "X4/22f3 (fuse 3)" or "Lines"

As a test, I measured from pins 4 and 5 to the opposite grounds:

11 > 4 reads good, but now 14 > 5 reads 0V

So it appears the ground at pin 14 is faulty.

I found the attached document ECI-powersupply.pdf (apologies to the original poster/source, I don't recall where I found it) that states pin 14 is the "Ground for left ignition module".

Questions:

1) I think I read somewhere that MB refers to the US-drivers side (7-12) as the 'left' side of the engine - is that correct? If so this would match my fault
2) Does anybody know where pin 14 of the N91 harness ("Ground for left ignition module") goes to so I don't have to dismantle my entire wiring loom? It is a solid brown wire
3) Is my only choice to trace the entire wire looking for cuts/splits/fraying?
4) Does anyone know where "X4/22f3 (fuse 3)" is located?

Any general tips on tracing the ground wire would be appreciated.

Thanks in advance