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 an TP sensor signal voltages lower than possible in a normally operating 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 volt for 1 second.
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 Symptoms .
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.
-
If the TP signal measures less than 0.25 volt, then the fault exists.
-
This test simulates the DTC P0123 (high voltage). If the VCM recognizes the high signal voltage, the VCM and the wiring are okay.
-
This test simulates a high signal voltage in order to check for an open in the TP signal circuit.
-
This step checks the 5 volt reference circuit for an open, short to ground, poor connection, or a faulty VCM.
-
The VCM terminals Gray 12 and Gray 27 are spliced together inside the VCM. Check the 5 volt reference circuits and all the components on the 5 volt reference circuits.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear DTC Information function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the scan tool display a throttle position signal less than the specified value? | 0.25V | |||
Does the scan tool display the TP signal voltage greater than the specified value? | 4.0V | |||
Probe the TP sensor signal circuit with a test lamp connected to B+. Does the scan tool display a TP sensor voltage greater than the specified value? | 4.0V | |||
5 | The DTC is intermittent. Are any additional DTCs set? | -- | Go to applicable DTC table | Go to Diagnostic Aids |
Check for an open in the 5 volt reference circuit. Was a problem found? | -- | |||
Check the 5 volt reference for a short to ground. Was a problem found? | -- | |||
8 | Check the TP sensor signal circuit for an open. Was a problem found? | -- | ||
9 | Check the TP sensor signal circuit for a short to ground. Was a problem found? | -- | ||
10 | Check for poor connections at the TP sensor connector Was a problem found? | -- | ||
11 | Check for a poor connection at the VCM. Was a problem found? | -- | ||
12 | Repair the circuit as necessary. Refer to Wiring Repairs in Repair Instructions. Is the repair complete? | -- | -- | |
13 | Replace the faulty TP sensor. Refer to Throttle Position Sensor Replacement in Repair Instructions. Is the replacement complete? | -- | -- | |
14 |
Is the action complete? | -- | -- | |
15 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
16 | Use the scan tool in order to display the Capture Info and the Review Capture Info functions. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
