Error codes causing LP not to work...
 

Could someone tell me why it is that when a MAP sensor triggers the check engine light that the LP stops coming on for 3 sec before you start the truck? Why would a MAP sensor code have anything to do with this?

Secondly what symptoms do you have if the bypass valve on the VP44 isn't working properly?

My truck is 02, but I with you 100%. The MAP code and LP run don't seem related. I am only guessing that you have separate problems. I have thrown a few MAP codes myself.

This is how the LP works on my truck. Turn the key to ON and LP runs for about 1 second. Turn the key to START and the LP runs continuesly while key is ON or for about 30 seconds if the key is turned to OFF.

Jim

Exactly how mine works except when the code is thrown it doesn't run until the engine has started. Very strange.