P0122

This article has been updated with bulletin No. 03-06-04-001












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 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 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

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

The VCM sets the DTC P0122. The VCM turns on the Malfunction Indicator Lamp (MIL) when P0122 is reported, and 1 failure has occurred.

CONDITIONS FOR CLEARING THE MIL/DTC
The VCM turns the MIL off 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 (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 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 Intermittents.

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.
7. The VCM terminals GR 12 and GR 27 are spliced together inside of the VCM. Check the 5 volt reference circuits and all the components on the 5 volt reference circuits.