Hey guys! So a little while ago my check engine light came on. After running diagnostics, on my 2004 F150 lariat, we found that my crankshaft position sensor was failing. After replacing it we found that the new sensor would not allow the engine to start and if it did, it would kill it in a few seconds. We also found that leaving the sensor intact but unplugged allows the truck to run completely fine. So basically, I have been running my truck with the check engine light on and the new crankshaft position sensor disconnected. Any ideas on why this may be the case?

 

Defective new part. Happens more often than you might realize.
.

 

Dorman brand? See if you can get a refund and replace with Motorcraft. I and others have had problems with Dorman junk, so much so,that I don't even bother with them for electrical.