Throttle Body: Description and Operation

Throttle Body Assembly:

IDLE AIR CONTROL (IAC) VALVE
The scan tool displays IAC pintle position in counts. 0 counts indicates the PCM is commanding the IAC pintle to be driven all the way into a fully seated position. This is usually caused by a vacuum leak.

The higher the number of counts, the more air is being commanded to bypass the IAC pintle. Refer to Idle Air Control System Diagnosis in order to diagnose the AC system. Refer to Rough, Unstable, or Incorrect Idle and Stalling, for other possible causes of idle problems. Component Tests and General Diagnostics

THROTTLE POSITION (TP) SENSOR
The TP sensor is mounted on the side of the throttle body opposite the throttle lever. It senses the throttle valve angle, and relays that information to the PCM. Knowledge of the throttle angle is needed by the PCM to generate the required injector control signals (pulse). For further information, refer to Information Sensors/Switches Description.

MASS AIR FLOW (MAF) SENSOR
The MAF sensor is mounted to the front of the throttle body, and is used to measure the amount of air entering the engine. The PCM uses this information to determine the operating condition of the engine and to control fuel delivery. For further information, refer to Information Sensors/Switches Description.

FUEL SYSTEM PRESSURE TEST
A fuel system pressure test is part of several of the diagnostic tables and symptom checks. To perform this test, refer to Fuel System Pressure Test. Fuel System Pressure Test