Code P0121, TP Sensor Range/Performance Problem "S" & "T" Series 4.3L (VIN W): Notes

Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .6 volt at idle to about 4.8 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by control module for fuel control and for most other control module control outputs.

1. TP sensor has a self-zeroing feature. If voltage is about .2-.9 volt, control module will use that value at closed throttle. If reading is out or range at idle, check for binding throttle linkage.
2. With TP sensor unplugged, voltage should go low if control module and wiring are okay.