Technical Description
The Throttle Position Sensor/Switch A Circuit is experiencing a high input.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles. While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Throttle Position Sensor (TPS) is a potentiometer that is mounted to the throttle body. Its purpose is to detect the angle of the throttle blade. As the throttle blade moves, the TPS sends a signal to the Powertrain Control Module (PCM), which is the main computer that operates the vehicle. The TPS is typically a three-wire sensor: a 5-volt reference from the PCM to the TPS, a ground from the PCM to the TPS, and a signal return from the TPS to the PCM.
The TPS sends the throttle position information back to the PCM through the signal wire. When the throttle is closed, the signal voltage is near 0.45 volts. At Wide Open Throttle (WOT), the TPS signal voltage will approach a full 5 volts. If the PCM detects a voltage higher than the normal upper limit, it will set the P0123 code.
Symptoms
Causes
A code P0123 may indicate that one or more of the following has occurred:
Possible Solutions
A good starting point is to check for technical service bulletins (TSB) specific to your vehicle. There may be a known issue with a known fix provided by the manufacturer, which can save you time and money during diagnosis.
If there are no symptoms, the simplest thing to do is to reset the code and see if it reappears.
If there are symptoms such as engine stumbling or hesitation, carefully inspect all wiring and connectors leading to the TPS. The problem is likely with the TPS wiring.
Check the voltage at the TPS (refer to a service manual for your vehicle for specific information). If the voltage spikes or is too high (over 4.65 volts with the key on and engine off), it indicates a problem. Carefully trace each wire from the TPS wiring harness to check for breaks, rubbing against other components, etc.
Other TPS sensor and circuit related DTCs: P0120, P0121, P0122, P0123, P0124
