DTC P0122 Throttle Position Sensor Low Voltage

Diagnostic Trouble Code (DTC) P0122

Throttle Position Sensor Low Voltage



Familiarity with the circuit


  • A 5 volt reference voltage signal and a ground to the Throttle Position (TP) sensor are supplied by the ECM and in return the TP is enabled to send a voltage signal back to the ECM relative to the throttle plate opening.
  • You will find the voltage signal changing from approximately 0.33 volts at closed throttle, to more than 4.3 volts at Wide Open Throttle (WOT).
  • The ECM utilizes the TP signal for controlling the fuel and also for most of the ECM controlled outputs the TP signal is supposed to be one of the most essential inputs used by the ECM for this purpose.




When will DTC set?

Task boosted after DTC sets

When will DTC clear?

DTC sets when

1) TP sensor voltage indicates a throttle voltage < 0.14 volts.

1) The Malfunction Indicator Lamp (MIL) will be seen to glow.

1) The MIL will go off after four consecutive ignition cycles where the diagnostic is found running faultlessly.



2) The ECM will begin to record operating conditions when the diagnostic fails.

2) A history DTC will automatically clear after 40 consecutive warm-up cycles faultlessly.



3) This information will be stored in the Freeze Frame and Failure Records will be boosted.

3) The Scan Tool can be used to unset all DTCs.



4) A history DTC is stored.

4) If the ECM battery feed is dissociated for more than 10 seconds.


5) The TP angle will default to 0% when the vehicle speed < 3 km/h (2 mph) and 10% when the vehicle speed >3 km/h (2 mph).




6) You will not see the scan tool showing the default value.





Diagnostic Tools

  • The information stored in the Freeze Frame data can be very handy in case DTC P0122 cannot be duplicated.
  • You can resort to using a scan tool information data to determine the status of the DTC.
  •  If the dc occurs intermittently, using the Diagnostic table may help remove the problem.



Purpose of the test

Number(s) below refer to the step number(s) on the Diagnostic Table.


1.The On-Board Diagnostic (EOBD) System Check which is carried out assists the technician to undertake some routine probes and store the freeze frame and failure records data on the scan tool if necessary. This creates an electronic copy of the data taken when as soon the test was done. The information is then stored on the scan tool for future use.

2.The TP sensor is devised for an auto zeroing feature. This will ensure that If the voltage reading ranges round 0.2 to 0.9 volts, the ECM will assume that the TP sensor is at a closed throttle position (0%).

5.This step boosts a high voltage signal to detect an open in the signal circuit.

6.Checking the 5v reference circuits for a short to ground will help in case any additional DTCs are set.

8.In this step, while examining the TP signal circuit, if the test light glows then the TP signal circuit is shorted to ground.

11.   The change of the ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.

13.   If there are zero flaws seen at this point and no additional DTCs set, you must consult  "Diagnostic Aids" for additional checks and information.