Vacuum Switch: Testing and Inspection

Chart C2-A:

Idle Up Circuit:

CIRCUIT DESCRIPTION:

The ECM receives a battery voltage signal if the vehicle's headlights and/or rear defogger are "ON." When the ECM sees this signal, it grounds the Idle-up VSV, allowing more air to enter the intake manifold, thus increasing engine idle speed.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if idle-up vacuum switching valve is operating normally.

2. Checks for an open or short to ground in BLK wire to ECM "ELS" terminal.

3. Checks for an open or short to ground in BLK wire to ECM "VISC" terminal.

DIAGNOSTIC AIDS:

Cracked or plugged hoses to idle-up VSV may cause improper idle conditions.