Description and Diagnosis Procedure

SYSTEM: A/C Idle Up Circuit

CIRCUIT DESCRIPTION
When the air conditioning operates (increased engine load), this circuit switch is on the Vacuum Switching Valve and increases the amount of bypass air to increase the idle speed, thus maintaining driveability.

DIAGNOSTIC PROCEDURE USING LEXUS HAND HELD TESTER
1. Connect the LEXUS hand-held tester and check operation of A/C idle-up Vacuum Switching Valve.
- If not OK proceed to step 2.
- If OK check and repair air hose and air pipe.
2. Check A/C idle-up Vacuum Switching Valve.
- If OK proceed to step 3.
- If not OK replace A/C idle-up 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 A/C idle-up Vacuum Switching Valve.
- If OK proceed to step 2.
- If not OK replace A/C idle-up Vacuum Switching Valve.
2. Check voltage between terminal ACV and body ground.
- If OK proceed to step 3.
- If not OK check and repair harness or connector.
3. Check air hose and air pipe.
- If OK check and replace Engine Control Module.
- If not OK repair or replace.