Description and Diagnostic Procedure

SYSTEM: Idle Air Control Valve Control Vacuum Switching Valve Circuit

CIRCUIT DESCRIPTION





This Circuit opens and closes the Intake Air Control Valve in response to the engine load in order to increase the intake efficiency (Acoustic Control Induction System). When the engine speed is 3,700 rpm or less and the throttle valve opening angle is 60° or more, the Engine Control Module turns the Vacuum Switching Valve ON and closes the Idle Air control Valve. At all other times, the Vacuum Switching Valve is OFF, so the Idle Air control Valve is open.





DIAGNOSTIC PROCEDURE USING LEXUS HAND HELD TESTER
1. Connect the LEXUS hand-held tester and check operation of Idle Air control Valve control Vacuum Switching Valve.
- If not OK proceed to step 2.
- If OK check for vacuum tank.
2. Check Idle Air control Valve control Vacuum Switching Valve.
- If OK proceed to step 3.
- If not OK replace Idle Air control Valve control Vacuum Switching Valve.
3. Check for open and short in harness and connector between EFI Main Relay and Engine Control Module.
- If OK check and replace Engine Control Module.
- If not OK repair or replace harness or connector.

DIAGNOSTIC PROCEDURE USING OBDII SCAN TOOL
1. Check Idle Air control Valve control Vacuum Switching Valve.
- If OK proceed to step 2.
- If not OK replace Idle Air control Valve control Vacuum Switching Valve.
2. Check voltage between terminal Acoustic Control Induction System and body ground.
- If OK proceed to step 3.
- If not OK check and repair harness or connector.
3. Check vacuum tank.
- If OK check and replace Engine Control Module.
- If not OK repair or replace.