Code P0123, Throttle Position Sensor: Notes

The Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .20-.74 volt or at idle to approximately 5 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by PCM for fuel control and for most of the PCM control outputs. On non-adjustable TPS sensors, each time voltage drops below 1.25 volts and stops, the VCM assumes this value as 0 throttle angle and measures percent throttle from this point on.

With Code P0123 set on 3.8L, Tech 1 will continue to display the actual throttle sensor voltage, but ignore TP signal and read mass air flow value for other PCM controlled functions, PCM will not allow 4th gear, TCC or cruise control operation, 1st, 2nd, and 3rd allowed.

NOTE: Test numbers refer to numbers on diagnostic chart.

With closed throttle, ignition on, or at idle, voltage at PCM TP sensor signal circuit should be .20-.74 volt.
With TP sensor disconnected, TP sensor voltage should decrease and Code P0122 will set. This test verifies that PCM and wiring are okay.
Probing ground circuit with a test light check sensor ground circuit. A faulty sensor ground circuit will cause Code P0123 to set.