Code P1639 5 volts reference circuit 2

Thanks for the reply. I need to know what other sensor is on the 5v reference circuit 2. Also was thinking that I may have a short to voltage problem instead of short to ground. I have taken the wiring harness apart going to the fusebox and found nothing wrong with the 5v reference wire on my TP sensor.

At the TP sensor only a 3 wire sensor. Grey 5v ref black sensor ground blue signal. 2002 has the cable throttle. I just unhooked the fuel tank pressure sensor and my 5v reference at the tp sensor is still high.

This the 5v reference circuit two. It shouldn't affect the circuit 1 5v reference circuit.

I replaced the engine in this truck and now 2,000 miles later I am getting this problem so I'm pretty sure that it is a wiring harness issue just need to narrow it down.
If I can find out all the sensors on that number 2 circuit then I can check the harness going to each one. Any wiring diagram will be very helpful. Thanks.

5v reference circuit 2 is reading 8.4 volts. This circuit goes to the tp sensor. Inside the pcm it is connected to the sensors. I just don't know what other sensors are controlled by this 5v circuit.

Thanks that should help me out. I will have to study it later. I work night shift and about to go to work now. Thanks again for your help.

I think that I have a bad PCM at the tp sensor and the fuel tank pressure sensor I have 5v sometimes with key on. I crank the truck and both go to 7 or 8. Switch off truck then back on and voltage doesn't go back to 5. Leave it off for a few minutes and I have 5.

Thanks. But, I don't have the capability to program the computer. I do apologize for not letting you know earlier but this truck is a 4x4. Was wondering if the wiring diagram for that is available. I need to check the position encoder motor and sensor. Should be something like a 5v reference to the range position sensor to let the computer know what position the transfer case is in.

Thanks again. I have the older style of encoder motor with two plugs. One plug is 4 wire for motor and a 6 wire for position sensor.

The newer ones have one plug with 10 wires the older ones have two plugs. One with 4 wires to control the motor and one with 6 wires to go to the position sensor. It is the same setup just two plugs instead of one. The 8v reference will be on the 6 wire plug going to the range position sensor on the encoder module. Thanks again for your help and patience. I need to get me a set of those diagrams. I like the Chevrolets and GMCs from that era 20000 to 2006.

The truck is my son's. We just got it about 2 months ago and the oil pump went out spun a main bearing so we had to replace the motor. Now a few wiring issues. He is 16 so he is getting some valuable experience working on his truck.