P0122

DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

Wiring Diagram:

Circuit Description

The Throttle Position (TP) sensor provides a voltage signal which changes relative to the throttle blade angle.

The TP sensor signal voltage varies from about 0.5 volts at idle to about 4.5 volts at Wide Open Throttle (WOT). The TP sensor signal is one of the most important inputs used by the VCM for controlling the fuel and for most of the VCM control outputs.

Each time the voltage drops below 1.25 volts and stops, the VCM assumes this value as 0 throttle angle. The measures the percent throttle from this point on. The DTC is a type A DTC.

Conditions for Setting the DTC

The following conditions will set the DTC:

- Engine running
- TP sensor voltage is less than 0.15 volts

Action Taken When the DTC Sets

Important: The scan tool will not indicate a default value.

The VCM sets the DTC P0122. The VCM turns ON the MIL when P0122 is reported, and 1 failure has occurred.

Conditions for Clearing the MIL/DTC

The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids

The scan tool reads throttle position in volts. The TP should read about 0.45 to 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 volt reference circuit or the TP sensor signal circuit results in a DTC P0122.

Refer to the Intermittent Conditions.

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.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2. If the TP signal measures less than 0.15 volt, then the fault exists.
3. This test simulates the DTC P0123 (high voltage). If the VCM recognizes the high signal voltage, the VCM and the wiring are okay.
4. This test simulates a high signal voltage in order to check for an open in the TP signal circuit.
6. This step checks the 5 volt reference circuit for an open, short to ground, or a poor connection, or a faulty VCM.