DTC P0123: Throttle Position (TP) Sensor, High Input: Condition

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when Powertrain Control Module (PCM) detects input voltage from TP sensor is more than 4.79 volts after ignition is turned on. This is a continuous monitor. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. Possible causes are:

TP sensor malfunction.
Open or short circuit between TP sensor and PCM.