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 higher 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 greater than 4.7 volts for 1 second.
Action Taken When the DTC Sets
Important: The scan tool will not indicate default values.
When the P0123 is reported and 1 failure has occurred, the VCM sets the DTC P0123, and the VCM turns ON the MIL.
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 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.
This DTC will result if the TP ground circuit is open or the TP signal circuit is shorted to the voltage.
Refer to the Symptoms .
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
If the TP signal measures greater than 4.8 volts, then the fault exists.
-
The TP signal voltage is below 0.2V with the TP sensor disconnected (if the VCM and the wiring are okay).
-
This step checks the sensor ground circuit for an open.
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 TP sensor voltage greater than the specified value? | 4.8V | |||
Does the scan tool display a TP sensor voltage less than the specified value? | 0.2V | |||
4 | The DTC is intermittent. Are any additional DTCs stored? | -- | Go to applicable DTC table | Go to Diagnostic Aids |
5 | With a DMM connected to ground, probe the 5V reference circuit (at the TP sensor electrical connector). Is the voltage greater than the specified value? | 5.2V | ||
Probe the TP sensor ground circuit (at the TP sensor electrical connector) with a test light connected to B+. Is the test lamp ON? | -- | |||
7 | Check for poor connections at the TP sensor connector Was a problem found? | -- | ||
8 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement in Repair Instructions. Is the action complete? | -- | -- | |
9 | Check for a short to voltage in the TP sensor signal circuit. Was a problem found? | -- | ||
10 |
Is the voltage greater than the specified value? | 5.2V | ||
11 | With a DMM connected to ground, measure the voltage on the VCM connector terminal Gray 27 (C3-27). Is the voltage greater than the specified value? | 5.2V | ||
12 |
Is the voltage greater than the specified value? | 5.2V | ||
13 | Repair the short to voltage on the 5V reference circuit. Refer to Wiring Repairs in Repair Instructions. Is the action complete? | -- | -- | |
14 | Check the sensor ground circuit for an open. Was a problem found? | -- | ||
15 | Repair as necessary. Refer to Wiring Repairs in Repair Instructions. Is the action complete? | -- | -- | |
16 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement in Repair Instructions. Is the action complete? | -- | -- | |
17 | Repair the short to voltage on the 5V reference circuit. Refer to Wiring Repairs in Repair Instructions. Is the action complete? | -- | -- | |
18 |
Is the replacement complete? | -- | -- | |
19 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
20 | Use the scan tool in order to display the Capture Info and the Review Capture Info functions. Are there any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
