P0122

Diagnostic Chart:

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.

CONDITIONS FOR SETTING THE DTC

The engine is running

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 the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

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 Symptoms. Testing and Inspection

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. 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, a poor connection, or a faulty VCM.

7. The VCM terminals CLR 12 and CLR 27 are spliced together inside the VCM. When checking the 5 volt reference for a short to ground, both the 5 volt reference circuits and all the components on the 5 volt reference circuits must be checked.