Chased a ghost code on a Cummins ISX for 2 hours before finding the real problem

I was under a 2015 Peterbilt outside of Tulsa last Tuesday, and it kept throwing a camshaft-crankshaft correlation error even after I replaced the sensors. Turned out the wire harness was chafed against the engine block right behind the fuel filter housing, just barely grounding out on vibration. Has anyone else run into random wiring issues that looked like a sensor failure at first?

2 comments

2 Comments

craig.tessa1mo ago

Drove myself nuts with a similar thing on a 2018 Freightliner last spring. Swapped out two different crank sensors, a cam sensor, and even the ECM relay before I realized the wire was rubbing on the oil filter housing bracket. Spent a solid 3 hours cussing under a truck in the Texas heat, only to find it was just a little frayed spot I could fix with electrical tape. My wife thinks I'm a genius mechanic, but honestly I'm just good at making the simple stuff look hard lol.

mary_patel591mo ago

Oh man, I gotta disagree with this whole "wiring gremlin" thing. I've been turning wrenches for 25 years and I'd bet my toolbox that 9 times out of 10 when you think it's a chafed wire, you're actually chasing a bad sensor that was already borderline. The real problem is people don't test the sensors properly before swapping them out. You spent 2 hours on a hunting trip when a simple wiggle test on that harness would have found it in 10 minutes. I mean, yeah, craig.tessa's story sounds familiar, but he had to swap all those parts because he didn't check the basics first. A good mechanic wouldn't need 3 hours of cussing under a truck in Texas heat when the real fix is just buying a $10 continuity tester and spending 5 minutes with it.