Ford Mustang Service Manual: Idle Air Control (IAC) Valve - 3.8L

Electronic Engine Controls (Description and Operation)

The electronic engine controls consist of the following:

  • powertrain control module (PCM)
  • throttle position (TP) sensor
  • idle air control (IAC) valve
  • engine coolant temperature (ECT) sensor
  • cylinder head temperature sensor
  • camshaft position (CMP) sensor
  • crankshaft position (CKP) sensor
  • mass air flow (MAF) sensor
  • intake air temperature (IAT) sensor
  • heated oxygen sensor (HO2S) - front
  • catalyst monitor sensor - rear
  • wheel speed sensor

The powertrain control module needs the following inputs to calibrate the engine correctly:

  • crankshaft position
  • engine rpm
  • engine load (manifold pressure)
  • atmospheric (barometric) pressure
  • engine coolant temperature

The throttle position sensor:

  • sends the powertrain control module a signal indicating the throttle plate angle.
  • is the main input to the powertrain control module from the driver.

The idle air control valve:

  • controls bypass air around the throttle plate at low speeds.
  • is controlled by the powertrain control module.

The cylinder head temperature sensor:

  • provides a gauge signal for coolant temperature.
  • is mounted on rear of LH cylinder head.
  • sends the powertrain control module a signal indicating engine temperature.
  • resistance decreases as coolant temperature increases.

The camshaft position sensor:

  • sends the powertrain control module a signal indicating camshaft position, used for fuel synchronization.

The crankshaft position sensor:

  • sends the powertrain control module a signal indicating crankshaft position.
  • is essential for calculating spark timing.

The mass air flow sensor:

  • sends the powertrain control module a signal indicating mass air flow rate of air entering the engine.

The intake air temperature sensor:

  • sends the powertrain control module a signal indicating the temperature of the air entering the engine.

The heated oxygen sensor:

  • has the ability to create a voltage signal depending on exhaust oxygen content.
  • provides feedback information to the powertrain control module used to calculate fuel delivery.

The rear catalyst monitor sensor:

  • monitors oxygen content after the oxygen flows through the catalytic converter.
  • provides a voltage to the powertrain control module used to calculate catalytic converter integrity.

The wheel speed sensor:

  • sends a signal to the powertrain control module indicating wheel speed.
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