Diagnostic Trouble Code (DTC) P0123 Throttle Position Sensor High Voltage

Diagnostic Trouble Code (DTC) P0123

Throttle Position Sensor High Voltage



Knowing the Circuit:


  • Controlling the idle speed taking the throttle body itself is what the purpose  of the MTIA (Main Throttle Idle Actuator) is.
  • The throttle is particularly devised for low opening angle (05, 195).
  • The features of the airflow differ for low and high opening angles.
  • This circuit has a gradient of the mass air flow function of TPS which is lower for small angles that allow it to be more accurate while handling the idle speed control.
  •  A classical Bowden cable actuates mechanically the idle speed throttle.
  • A voltage signal that changes in proportion to the throttle plate angle is catered by the throttle position sensor (TPS).
  • It will be seen that the signal voltage will change from about nearly 5.0 V at idles to about 0.2V to 0.4 V at wide-open throttle.
  •  The TPS is one of the most indispensable inputs needed by the ECM for fuel control and other functions such as idle, wide open throttle, deceleration enleanment, and acceleration enrichment.



                                      Question: When does the DTC set?

Answer: DTC sets when the TPS voltage is above 0.3V.


Task Boosted When DTC sets

When Does DTC clear?

1) The Malfunction Indicator Lamp (MIL) glows.

1) The MIL will stop glowing after four successive ignition cycles in which the diagnostic runs smoothly.


2)   The ECM will record information of operating conditions at the time the diagnostic fails which will be stored in the Freeze Frame and Failure Records will buffer.


2) A history DTC will clear after 40 consecutive warm-up cycles without a fault

3) A history DTC will be stored.


3) Scan Tools can be used to clear all DTC(s)

4) The coolant fan will turn ON

4) Disconnecting the ECM battery feed for more than 10 seconds.


5) The ECM will default to 20°C (68°F) for the first 60 seconds of the engine run time, and then 92 °C (198 °F).




6) This defaulted value will not be shown by the scan tool.






Diagnostic Assistance


  • The information stored in the Freeze Frame data can be reverted to in case the DTC P0123 cannot be duplicated.
  • To estimate the status of the DTC the scan tool will be handy.
  • Consulting the DTC P0121 diagnostic table may help to avert ant error problem if it is found that the DTC occurs intermittently.
  • The voltage should ideally read between 0.20 V and 0.90V and rise steadily to over 4.5V at WOT if  the ignition is ON and the throttle is closed.
  • DTCs P0123 and P0113 stored at the same time could be the result of an open sensor ground circuit.