Throttle Actuator Control - drive by wire

Your vehicle does not have a idle air control valve , don't know how you came up with that .(code reader ? ) Your vehicle has what is called drive by wire - electronic throttle control . Or as GM calls their system TAC - throttle actuator control .

Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to, the following:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• the engine control module (ECM)
The APP sensors and the throttle body assembly provide inputs to the ECM to ensure accurate calculations and control of the TAC system.
Accelerator Pedal Position (APP) Sensor
The APP sensor is mounted on the accelerator pedal assembly. The APP is actually 2 individual APP sensors within 1 housing. These are 2 separate signal, low reference, and 5-volt reference circuits. The APP sensor 1 voltage increases as the accelerator pedal is depressed. The APP sensor 2 voltage also increases as the accelerator pedal is depressed, but the voltage range for sensor 2 is approximately half of sensor 1.


Your best bet mite be to take it to a qualified repair shop that has the right diagnostic tools to find the problem .

https://www.youtube.com/watch?v=x4xcQSRAgFI

https://www.youtube.com/watch?v=oPPLAHSSluw

Probably caused by the electronic throttle control . How many miles on the vehicle ? The gas pedal has position sensors that the PCM - engine computer uses to know how much to open the throttle plate .
Drive by Wire Function and diagnostics by Wells
What engine ?
The throttle actuator control (TAC) system is used to improve emissions, fuel economy, and driveability. The TAC system eliminates the mechanical link between the accelerator pedal and the throttle plate. The TAC system eliminates the need for a cruise control module and idle air control motor. The following is a list of TAC system components:
• The accelerator pedal assembly includes the following components:
- The accelerator pedal
- The accelerator pedal position (APP) sensor 1
- The APP sensor 2
• The throttle body assembly includes the following components:
- The throttle position (TP) sensor 1
- The TP sensor 2
- The throttle actuator motor
- The throttle plate
• The engine control module (ECM)

Drive by wire , electronic throttle control . What is it you would like to know Mr. Woods ? Can throttle cause car not to crank ? What year Buick ?
STARTING DISABLED SERVICE THROTTLE
Throttle Actuator Control (TAC) System Description for the 4.6L engine or Throttle Actuator Control (TAC) System Description for the 3.8L engine.

Purpose
The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:
• Accelerator pedal position (APP) sensing
• Throttle positioning to meet driver and engine demands
• Throttle position sensing
• Internal diagnostics
• Cruise control functions
• Manage TAC electrical power consumption
The TAC system includes the following components:
• The APP sensors
• The throttle body assembly
• The powertrain control module (PCM)

Drive by Wire training

Well an oil change is probably not the cause.
What IS it doing? You're telling me what it isn't doing...
Does the motor rev up?

You need to have it checked for DTC'S - diagnostic trouble codes , There is a problem with throttle actuator control (TAC) - electronic throttle control !
Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to the following:
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The accelerator pedal position (APP) sensors

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The throttle body

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The powertrain control module (PCM)
Each of these components interface together to ensure accurate calculations and control of the throttle position (TP).


Drive by Wire Function and Diagnostics by Wells