P0122
DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage
Circuit Description
The throttle position (TP) sensor is a potentiometer. The control module supplies the TP sensor a reference voltage, a 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 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 signal voltage is less than 0.25 volts for 1 second or more.
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs and fails.
- The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.
Conditions for Clearing the MIL or 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 a scan tool in order to clear the DTCs.
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). The scan tool also reads the throttle angle as a percentage. 0 percent equals closed throttle, 100 percent equals Wide Open Throttle (WOT).
An open or short to ground in the 5 volt reference circuit or the TP sensor signal circuit could result in a DTC P0122.
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.
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 volt 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 volt reference circuits OR an internally shorted sensor may cause this DTC to set. In order to determine the location of a shorted 5 volt 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 volt reference circuit for a short to ground, both the 5 volt reference circuits must be checked.
