The code reader is giving me a code for cylinder #1 misfire and Crankshaft position sensor!

I just replaced the position sensor 500 miles ago. Could it be the plug or plug wire for cylinder #1? Or the coil pack?

https://www.gmforum.com/buick-172/an...n-making-post/

My 1997 Lesabre has 139,000 miles on it. The engine is a 3800 V6. The only maint I have ever completed was the crankshaft position sensor.

First thing I would do, is go to 1/4 coil and remove ignition wires, one at a time, and look for corrosion/carbonning on the coil terminals....if ok, then check coil output with a spark tester........

Do you have any idea of how many miles are on the wires and plugs?

Could also be a bad injector.....

But I would be checking secondary ignition first....

other possibilities are valves, cam lobes, etc.

I visually checked plug and wire and they looked fairly new. So I decided to replace the 1/4 coil. Now the car is running perfectly smooth again. So I guess I learned that the code reader can give incorrect information.

No, the code reader gave correct information. The PCM detected a misfire on #1. And that'* exactly what it was seeing. Though, the coil may have been connected properly and the PCM may see it, but it may fail in such a way that still works, but poorly, thus causing the misfire. In this case, the misfire was probably due to a weak spark.

I would agree that yes it gave correct info about misfire on #1 but respectfully disagree about it not giving incorrect info. It did give me a code for crankshaft position sensor which was not the problem. Anyway, it is smooth as can be now...happy GM driving to all