The Computer reads three positions from the TSP. They are CT (Closed Throttle), PT (Part Throttle) and OT (Open Throttle).
The computer will go to Open Loop when its math say it is at OT. It takes the CT voltage when the engine is started each time (0.6-1.2VDC) and this is why you should never touch the Throttle when starting the engine. It then uses math to come up with the PT and OT ranges of voltages. If the CT is not in the 0.6-1.2VDC then the math will be off and it may not ever think it is at OT. The Throttle may not have to be all the way open to be be in OT.
I like to see the closed throttle position to be about 0.9VDC. So the closed throttle position voltage will determined at what voltage the computer thinks it is in OT (some where less than 4.95 VDC).