Throttle Position Sensor Voltage Clarification

[sanfriz]

I am trying to work out a new problem with my 5.4 DBW. Throttle blade only opens about 1/4in at WOT. I put new injectors in, was running good, stopped for gas and when I started it back up it ran like crap. Tried to adjust the tune, clear the codes, and put on new GM MAP. I don't believe the tune has anything to do with it because it was running good and all I did was turn off and back on.

When I add the Throttle Position Sensor Voltage to my scanner it reads 0.00 all the time. I manually checked the voltage at the plug and can confirm it's there. What is the scanner reading when it shows me 0V? From what I can find on searches it looks like it should give me an output reading.

I already ordered another TB, but if that doesn't work what am I looking for?

Throttle position % and desired % show very close so I don't think that's the issue.

Thank you for your help.

[TheMechanic]

With no build data, no tune, and no log it is very difficult to give you a starting point.
Suggestion is to find a professional scanner to check TPS. If in fact it is zero I would suggest checking for codes. If no codes check to make sure you didn't set them to no report. If so re-enable them and get a code to set and perform a diagnostic. A likely culprit is the TPS sensor in the throttle body itself. You can either replace the throttle body or just the TPS. I base this on probability only. This is not a diag.

[blindsquirrel]

There should be two TPS voltages in a DBW throttle body, TP1 and TP2 (which you can definitely look at with a real scan tool built for doing diagnostics, but HPT is a tuning tool that sometimes accidentally works for diagnostics). Only the older cable TBs have a single TPS voltage. Looking at the Description and Operation section in your service manual (you do have the service manuals if you're trying to do this yourself, right?) should give you an overview of how the system works.

[sanfriz]

Thank you. I didn't post a tune because it was running ok until I shut if off for a few minutes to pump gas. After starting it up it ran bad like it did before the new injectors, so I thought maybe it lost the new data. I did another write and nothing changed so I don't believe the tune would do that when there were no changes. It's a 5.3/4L80 sloppy 2 cam with DW1000cc injectors. Has a turbo but I pulled all the charge pipes off making sure it wasn't the problem. I was just confused why I could log the TPS voltage in the scanner and it was showing 0. I have since received the pin out voltage data for the plug and all seems to be fine. I was told I might need to add another ground to the plug ground wire, but it seems to be strong. If the new TB doesn't work I'll do that next.

My new TB will be here tomorrow so I will start with that first.

Only thing to note on the scanner is my cylinder mass won't go over 60 and my MAP won't read over .75 BAR. Now that I think about it the TB not opening was obvious. First DBW car so I didn't think about it.