Rep Power: 0

I had/have a problem with my 2007 Civic going in to limp home mode at 75 mph (over 3000 RPM). Two garages gave up on the problem, so I took it to the dealer. The dealer said that a non OEM serpentine belt caused the crankshaft sensor to mis read. Does this make sense?

Yours R Kent

 
Rep Power: 518

Absolutely. It's a real phenomenon, albeit a rare one. (I've read about it but never witnessed it myself)
Due to materials used in the construction of some belts, static electricity builds up while running and discharges as a spark. PCM can freak out if the spark discharges anywhere near wiring or sensors.

Does it set any fault codes when it goes to limp mode?
If a genuine OEM belt solves the problem, that's a cheap fix.

 
Rep Power: 0

When it first happened, there were no codes. I would just stop, turn off the engine, turn it back on, the cel light would go off and it would run fine. As time went on, there were codes that indicated "mis-fire on all cylinders.

R. Kent

 
Rep Power: 518

Come to think of it, I've also heard of "fat spots" in a belt causing odd misfire code issues.

Another thought... If the car ever got a replacement engine block or engine, the installer should have performed a CKP relearn at that time. If that step was skipped, maybe that could be related to the issue you have now.

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Were you ever able to FEEL it misfire or run any different while the problem occurred?

So is a new belt from the Honda dealer installed now, and did it solve the problem?