P0122
DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage
Circuit Description
The throttle position (TP) sensor is a potentiometer. The control module (PCM/VCM) supplies the TP sensor a reference voltage, signal, and ground circuits. When the throttle is depressed, the TP sensor signal rises to near the reference voltage. When the throttle is released, the TP sensor signal decreases from the reference voltage. The control module monitors the TP sensor signal circuit voltage in order to determine the throttle blade's angle, or opening.
This DTC is designed to detect a TP sensor signal voltage lower than the possible operating range of a normally functioning TP sensor
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The TP sensor signa voltage is less than 0.25 volts for 1 second.
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tools Freeze Frame and Failure Records.
Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22° C (40° F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70° C (158° F) during the same ignition cycle.
- Use the scan tool Clear Information function
Diagnostic Aids
The scan tool reads throttle position in volts. The TP should read about 0.45 - 0.85 volts with the throttle closed and the ignition ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward wide open throttle (WOT).
An open or short to ground in the 5 volts reference circuit or the TP sensor signal circuit results in a DTC P0122. Refer to the Symptoms.
Scan the TP sensor signal while depressing the accelerator pedal with the engine stopped and the ignition ON. The display should vary from below 1.25 volts (1250 mV) when throttle was closed, to over 4.5 volts (4500 mV) when throttle is held at the wide open throttle (WOT) position.
An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs.
Step 1:
Steps 2 - 5:
Steps 6 - 9:
Steps 10 - 15:
Steps 16 - 20:
Steps 21 - 22:
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. If the TP signal measures less than 0.25 volt, then the low voltage condition exists.
5. If the VCM recognizes the high signal voltage, the VCM and the wiring are okay.
8. The 5 volts reference of the VCM supply is shared by the MAP, FTP, TP, and EGR position sensors. A short to ground at ANY of the sensors 5 volts reference circuits OR an internally shorted sensor may cause this DTC to set. In order to determine the location of a shorted 5 volts reference supply, disconnect the sensors one at a time beginning with the MAP sensor.
12. The sensor connectors must remain disconnected while the VCM C3 connector remains connected for this step. The VCM terminals C3 12 and C3 27 are spliced together inside the VCM. When checking the 5 volts reference circuit for a short to ground, both the 5 volts reference circuits must be checked.