Serious question, are we too quick to blame the ECM for a no-start?

I was out on a job near Tulsa last spring, a 2015 Freightliner with a Cascadia that would crank but never fire. The shop before me had already swapped the ECM and the injector harness, probably $2,800 in parts, and the customer was furious. I started checking the basics, and found the camshaft position sensor had a chafed wire where it rubbed against the mount bracket. Five bucks for a used sensor from my bin, twenty minutes to solder and tape it, and it fired right up. That made me wonder if we lean on the computer too fast when the simple stuff gets ignored, but at the same time I've seen guys chase loose grounds for two days while a factory scan tool would have flagged the ECM communication issue in one pass. So how do you all decide when to trust the code versus when to trust your eyes first? Has anyone else had a job where the computer diagnosis sent you down a rabbit hole that a basic voltage test would have solved in ten minutes?

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lopez.brooke7d ago

Feels like this gets framed as some big debate but honestly it's just how the job goes, sometimes codes point you right and sometimes your eyes do. Doesn't mean we're "too quick" to blame anything, just means diagnosis is messy.

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