Hi all -

I have a 2010 Express 3500 with just about 200k miles. About three weeks ago, the CEL came on. Scanned and read a misfire on #7. I took the opportunity to replace all plugs, plugs wires, and coil packs.

Misfire persisted. So, I pulled the #7 injector and replaced it. I knew as soon as I pulled it that it was probably not the problem, and sure enough, the misfire persisted. (somewhat unrelated...I didn't pull the full fuel rail, but I'm curious if people do it from the engine bay or the passenger area. Passenger area seems way easier except I couldn't quite understand how you would deal with the harness that is essentially locking it down)

Then I took to probing electrical connections. I don't have a great multimeter, but i verified wire continuity from the ECM connector to the spark and fuel plugs, and verified good 12v power. What I don't see is any signal pulsing. Though again, my multimeter is a cheap $20 model and may not have the sensitivity to detect and/or display relatively fast DC switching. And the AC side only goes down to 200V.

I'm essentially at the end of my diagnostic capability. I did pull the ECM out of the engine bay and the pins all seem fine, and the seals do not seem compromised. Likewise, the female ports on the connector side all seem like they are making good contact and are not spread (though I essentially checked this by feel - I have not desired to take apart the connector).

Any other things I can try before replacing the ECM? I live in a very rural area (the closest auto parts store is about 70 miles away) so unfortunately taking it in for a more comprehensive code scan is at present not an option.