Things are getting confusing , My 98 GM K1500 6.5 is driving me nuts. I replaced the crank sensor and all seemed well, even PMD's that were thought to be bad worked fine. I installed a #9 resistor ,the truck always lacked power compared to my 97 , but it still ran good.
Now I start getting the check gauges light and Oil pressure drops to 0 when I brake and idle in drive.. Also it develops some slight hesitation accelerating lightly, and heavily till the RPM's come up to 2000 +. Power has increased at highway speeds after changing the CPS.
Then the High beams stop working, and the Volt gauge drops to 12 V from the normal 16. I can't find the issue , and the low RPM issue continues to get worse, so I plug in the spare PMD in desperation. Thinking an alternator is on the shopping list but now It is back charging at 16V, still no high beams, and oil pressure remains good when braking and at idle in drive. RPM is the same as when the oil pressure was dropping.
None of these things seem possible to be related to a PMD or CPS . A new switch seems in order for the High Beams, but is it possible that a PMD or resistor can cause the oil pressure gauge to read incorrectly, and the check gauge light to come on? Doesn't seem possible , but changing a PMD made the oil pressure gauge read normal , and after switching the PMD I lost cruise control. can a PMD also cause cruise control loss? Again it doesn't seem possible , or related.

 

yes bad PMD will cause no cruise control

 

Switched back PMD's and cruise is fine again, and the oil pressure guage drops low and check guage light comes on again at idle in drive.

This makes no sense, but it is what it is.