DTC P2123 OBDII code setting indicates that the Powertrain Control Module (PCM) detected a high voltage input in the Throttle Position Sensor (TPS) circuit. The “D” description refers to a particular area of a circuit or sensor. For this reason, you should consult a reliable source of information about your vehicle for details. This code is only set on vehicles equipped with Drive-By-Wire systems (DBW).
DBW systems are controlled by the PCM, through a throttle motor actuator, and multiple Throttle Position Sensors. The sensors typically have a 5-volt reference and ground signal. These sensors are potentiometers that complete the corresponding circuit. Their resistance varies in response to the movement made by the circuit board contacts and this causes fluctuations in the circuit resistance and signals input voltage to the PCM.
If the input voltage exceeds the limit set by the manufacturer for more than a certain time, this code is set and the Check Engine light illuminates.