Had intermittent trouble with starting last week. Now no starting or spark at all. Have constant 12 volts to coil pack, but no pulse signal from crank sensor. Checked for voltage at sensor w/ignition switch "on" and no voltage. Relays and fuses ok. Looking toward PCM. Any way of testing PCM before taking the plunge of buying a new one or chancing a used one? Anyone have similar trouble? Engine is 4.2 six.

 

Finally found problem. Wire going to crank sensor was corroded about 1/2 inch above the plug. Replaced wire and sensor while I was at it. Running fine now. FYI I recently bought this truck and noticed a lot of corrosion and oxidation in the engine compartment almost like it had been sitting for several years. It has 130,000 miles on the clock! I don't think it has had a chance to sit. A mechanic I know told me this could be from using those brushless high pressure car washes. The water is recycled in a lot of these units except for the rinse water and all the salt from winter driving goes where? Yeah, pressure sprayed under your car! Just some food for thought.