1999 GMC Suburban Intermittent P0336 ODBII Code

My 99 GMC Suburban with a 7.4L engine has a issue where it won't start intermittently. It will crank but won't start. The error code I get is a P0336. When this happens, I do not get spark out of the plugs and no spark out of the coil. Compression on all cylinders is good (150PSI). Fuel pressure is good. After a few days it will start again. This seams to happen when it rains. I do keep the truck outside. I know the error code indicates an issue with the crankshaft positioning sensor (CKP). This problem has happened three times. Twice it was outside and this occurred after it rained. Once it happened inside my garage after I unplugged the Blue connector from the VCM to check pin 31 with a DMM for a signal back from the CKP. I also grounded pin 28 to the engine and to my ground lead on the DMM. Pin 31 is the signal back from the CKP and pin 28 is the ground for the CKP. Any help would be appreciated.