That's the code I'm getting on my 93 4.9 now. At first I got a code 47 I think, telling me to change the TPS. When I changed it, the motor still would not idle at all and was running rich. Wound up swapping the MAP sensor with another I had and the motor evened out. That's when I started getting the code for low voltage on the TPS.

I swapped it back out with the old one with no change. The motor runs fine, just idles a little high (@900) and the CEL stays on.

I'm not aware of any way to adjust the voltage. I tried to do a search on here, but have a poor connection. Some body help me out please.

 

Low voltage could be simple as poor connection with the TPS, bad TPS, or weak battery.

TPS output should be around 0.85-1.0 with throttle bracket touching the throttle plate stop screw and around 4.5 volts with throttle at WOT (wide open throttle)

Need to check with a DVOM , with the throttle body plates closed, what you have with key on, engine off.

I cant remember which wires need to be probed. I know the black is the common ground, but there is also orange and green. I believe the green Green wire is the correct one to test. Also check your reference voltage of 5 volts. If it's not within +- 2% of 5 volts, then you need to dig into that as a problem. Also you can check for good 5 volt reference from the IAT or the ECT sensor. See what the reference voltage shows for them and compare. Could also be poor connection to the PCM and if so, then you will chase your tail if you don't fix that 1st.