Crank Position Sensor
 

Ok, so I’ve got a 1997 Blazer and, very long story short, the timing chain cover leaks like the Exxon Valdez...I’m a weekend warrior when it comes to automotive maintenance, so when I rebuilt the top end of the engine after the lower intake manifold gasket failed, I was unaware of the need to drop the oil pan until I had already removed the old one. I would like to do it correctly now, because my daughter will be driving it. My question is, if I remove the crank sensor in order to change the cover, will I have to do a crank position re-learn? I had to do one when I changed the timing chain because, in swapping the crank sensor to the new cover I broke it, and obviously had to do a re-learn then, but I didn’t know if that was because I had installed a new one or does just removing it require a re-learn...

The answer is maybe! Factory info says yes, but they assume the way to do this is at the technician's fingertips. if you get a false misfire you will know then.

If you're replacing the timing cover (which you should be), it's definitely a good idea to do a relearn. If you were reusing the same cover, sensor, etc., you could probably get away with skipping it. But, like Les said, there's no harm in trying. If you get the misfire code, then do the relearn.