The reduced engine power happens because there is a problem with the electronic throttle control . Some people call it drive by wire ! The gas pedal has sensors inside , position sensors , connected electrical to the PCM - engine computer , the throttle body on the engine has a DC electric motor an also has position sensors . These are also connected to the PCM electrical . The PCM reads the position sensors which indicate how much your pressing on the gas pedal . then hopefully it opens the throttle the same amout .
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 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 accelerator pedal position (APP) sensors
• The throttle body assembly
• The engine control module (ECM)
Reduced Engine Power Mode
When the ECM detects a condition with the TAC system, the ECM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
• Acceleration limiting--The ECM will continue to use the accelerator pedal for throttle control, however, the vehicle acceleration is limited.
• Limited throttle mode--The ECM will continue to use the accelerator pedal for throttle control, however, the maximum throttle opening is limited.
• Throttle default mode--The ECM will turn OFF the throttle actuator motor and the throttle will return to the spring loaded default position.
• Forced idle mode--The ECM will perform the following actions:
- Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned OFF
- Ignore the accelerator pedal input
• Engine shutdown mode--The ECM will disable fuel and de-energize the throttle actuator.
GM Electronic Throttle Body Circuit Descriptions And Testing Tips
Tons of videos on youtube for these systems , there can be a variety problems , from wiring , worn out sensors , the DC motor , computer etc....