Electronic Throttle Control Description

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 (TPS) 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)

Question: 2004 envoy, 4.2l, engine idle is running very fast , throttle body is spotless. idles at 2000rpm at 30kph.
 Answer: If the throttle is spotless because you just cleaned it, and NOW it idles high, you would need to have the idle relearned. This is best done with a scanner, but can be done by driving on expressway for a few miles, then letting idle in gear for a few minutes. If this is not the case, then look for a vacuum leak. The intake manifold bolts tend to get loose.

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