A vehicle has an illuminated MIL and a DTC P0123 - TPS high voltage. Technician A says that an open signal return wire could cause this code. Technician B says that a shorted TPS could cause this DTC. Who is correct?

The correct response highlights that both technicians are correct regarding the potential causes of the DTC P0123 - TPS high voltage code.

An open signal return wire can indeed lead to an inaccurate signal being sent from the throttle position sensor (TPS) to the engine control unit (ECU). When there is an open in the signal return, the ECU may interpret the reduced or absent signal as a high voltage condition, leading to the specific code being triggered.

On the other hand, a shorted TPS can also generate this high voltage code. If the TPS itself is shorted internally, it may provide a higher voltage output than the ECU is expecting, directly causing the P0123 code to illuminate.

Understanding these mechanisms is crucial for diagnosing and resolving issues related to the throttle position sensor. By recognizing that either scenario can lead to the same code, technicians can better approach the problem and ensure a thorough investigation into the TPS and associated circuitry.