Poor running condtion

With the ignition switch on, measure the three voltages at the throttle position sensor. This has to be done with it plugged in by pack-probing the connector. You should find 0.2 volts on the ground wire, 5.0 volts on the feed wire, and between 0.5 and 4.5 (approximately), volts on the signal wire, depending on throttle position.

Your voltages are right but two of your labels are turned around. The 5.1 volts is the feed wire. The 1.9 volts is the signal wire, and that voltage will go up when you open the throttle. On all newer vehicles the Engine Computer learns the lowest voltage on the signal wire, which is at idle, and puts that in memory. Yours has slotted mounting holes and needs to be adjusted to a certain value. I don't know what that value is but around 0.5 volts is typical. If you have the service manual it should be listed in there. I'm trying to find the right manual but haven't had any luck so far.

I should have reread your first post. I was thinking you replaced the TPS but I see you're chasing a fault code. If the engine was running properly before and you didn't do anything to change the TPS adjustment, leave it where it is.

The fault code description leaves a lot to be desired. I come up with:

26 - quad-driver module (computer) circuit #1 fault

Normally that refers to the circuit in the Engine Computer that runs the injectors or ignition coil. I wonder if they're referring to the idle speed motor and they're calling it the throttle circuit. The voltages you found on the TPS would not set a fault code. Either there is an intermittent problem or we're looking at the wrong circuit. I need to do some more digging.