The Throttle Position (TP) sensor provides a voltage signal which changes relative to the throttle blade angle. The signal voltage varies from about 0.5 volt at idle to about 4.0 volts at Wide Open Throttle (WOT).

The VCM uses the TP signal, one of the most important inputs, for fuel control 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 the 0 throttle angle, and the VCM measures the percent throttle from this point on. The DTC P0123 is a type A DTC. The DTC P1122 is a type D DTC.

The DTC sets when the TP sensor is less than 0.15 volts.

The VCM stores the DTC in History if the VCM detects an intermittent problem.

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.

The VCM pins GR 12 and GR 27 are spliced together inside the VCM. When checking one of these circuits for a problem, also check the other circuit and the components on the circuit.

The scan tool reads the throttle position in volts. The scan tool should read about 0.45 to 0.85 volt with the throttle closed and the ignition switch turned ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward the Wide Open Throttle (WOT).

Also, some scan tools will read the throttle angle. 0% = closed throttle. 100% = WOT.

Scan the TP sensor while depressing the accelerator pedal with the engine turned off and the ignition turned on. The display should vary from below the 1.25 volts (1250 mV) when the throttle was closed to over 4.5 volts (4500 mV) when the throttle is held at WOT position.

A DTC P0123 will result if the TP ground circuit is open or the TP signal circuit is shorted to the voltage.

A DTC P0122 will result if an open or a short to ground in the 5 volt reference circuit or the TP sensor signal circuit.

Refer to Intermittent Conditions .

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

2. If the TP signal is less than 0.2 volt, then the fault is present.

3. This step simulates the DTC P0123: (high voltage) - If the VCM recognizes the high signal voltage, the VCM and the wiring are OK.

4. The VCM recognizes the voltage as over 4 volts, indicating that the TP sensor signal circuit and the VCM are OK.

5. This simulates a high signal voltage in order to check for an open in the TP sensor 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.