Powertrain Controls - ECM/PCM

Diagnostic Chart:

Diagnostic Chart (Cont'd):

Circuit Schematic:

IDLE AIR CONTROL (IAC) - RPM OUT OF RANGE
The idle air control (IAC) consists of a two coil stepper motor controlling a valve. The motor is used to move the IAC valve pintle in and out of a seat to control the amount of air that enters the intake manifold at idle.

DTC PARAMETERS

DTC 35 will set if:
^ Idle speed is greater than desired after PCM commanding the IAC motor closed.
^ Idle speed is less than desired after PCM commanding the IAC motor wide open.

DIAGNOSTIC AIDS
When attempting to diagnose an intermittent problem use the Scan tool[1] to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.

Intermittents or opens suspected to be at the connector can be detected by using Diagnostic Service Probe. Voltage can be read on both wires without disconnecting any connectors.

Check the tightness of the female terminal grip with a spare male terminal.

^ Desired idle is based on a look-up table but anything that requires an idle speed boost will affect desired idle.
^ The desired idle speed can be found in either the Scan tool or the service stall system.
^ IAC is controlled by the PCM with four pulse width modulated (PWM) outputs.
^ Cruise cable misadjustment may cause a high idle due to throttle plates being held open.
^ Inspect PCV valve and system.
^ Incorrect minimum idle air will cause a DTC 35.
^ Check wires for damage (contacting engine, brackets etc.) causing a short.

[1] Select Malfunction History from Scan tool Engine Control (EC) menu.