Chrysler Repair: tps voltage range questionable vs. service manuals, simple voltage divider, 5v supply

Question

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Followup To

Question -
first things first 1999 dodge dakota 3.9 v-6 auto 42re trans single cab.
my service manual says that at wot the tps sensor should read 4.7 - 5 volts, mine reads 3.75 with a snap-on scanner and double checked with a multi-meter, at idle it should read between .65 and .9 volts, and it does, i have checked the voltage to various sensors and they all ckeck out, but cannot figure out why the wot reading on my tps is one full volt below what it should be.the truck runs and will burn tires. email me back if you have any suggestions about my situation.
adam

Answer -
Hi Adam,
The tps is a simple voltage divider. One end of the resistor is supposed to have 5V on it, the other end is ground. The sensor on the shaft 'wipes' along the resistor and so its reading reflects where it is on the resistor.
So either the 5V supply is below what it should be or the tps wiper is not moving fully to the end of the resistor where the 5v is supposed to be present when WOT. I would measure the voltage between the two outside terminals of the TPS plug (one is 5V the other is sensor ground). And also check if the resistance between the middle pin and the outside pin of the TPS side of the socket that has 5V applied to it is near 0 ohms when you are WOT. That will tell you which it is: voltage supply from the PCM or defective tps. That same 5V supply is used by the MAP so if it is low the MAP will also be off-value.

Brand spankin new sensor the reason i got the new sensor is because the old one read the same wot voltage, thought the new sensor would clear it up, i have checked the voltage to the map sensor and it has 5 volts, could there possibly be two different sensors for that model year? i dont know the production month, but have witnessed problems like this before, i have not checked to see if the voltage corresponds to the throttle range in a linear pattern, which would mean chiltons might be wrong, but if the sensor didnot correspond in a linear pattern one would think that the sensor might be of the wrong callibration, i would like to think that chiltons is wrong, but one volt shy of the full 5 volts(20%) at wot could mean better mpg and more ponies(both major concerns). thank you for your timely reply, adam  

Answer
Hi Adam,
I would question the Chilton's spec. I don't have any manuals for the 3.9 V-6 but a Haynes for that time period and the smaller engines speaks of a WOT of 4 volts. So if everything is working well I would ignore the Chilton's  and forget it.
Roland