Idle Speed/Throttle Actuator - Electronic: Testing and Inspection

Diagnostic Chart - Part 1 0f 2:

Diagnostic Chart - Part 2 Of 2:

Idle Air Control Valve:

Circuit Description:
The engine control module (ECM)/powertrain control module (PCM) controls engine idle speed with the idle air control (IAC) valve. To increase idle speed, the ECM/PCM grounds the OPEN solenoid within the IAC valve. This action opens a plate within the IAC valve, allowing air to bypass the throttle plate. The ECM/PCM regulates (fast) idle speed via the IAC valve by increasing the opening of the air bypass port. To decrease idle speed, the ECM/PCM grounds the CLOSE solenoid within the IAC valve, thus allowing less air to bypass the throttle plate. The ECM/PCM regulates (slow) idle speed via the IAC valve by decreasing the opening of the air bypass port.

Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. Checks for open in power feed to IAC valve.

2. Checks IAC valve CLOSE circuit.

3. Checks IAC valve OPEN circuit.

4. Checks for an open or start to ground in BLK/BLU wire, a faulty IAC valve or a faulty ECM/PCM.

5. Checks for an open or short to ground in BLK/WHT wire, a faulty IAC valve or a faulty ECM/PCM.

6. Checks that IAC valve closes.

7. Checks that IAC valve opens.

Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Inspect the harness connector for backed out terminals, improper mating, broken lock, improperly formed or damaged terminals and for poor terminal-to-wire connection before component replacement.