Description and Diagnostic Procedure

SYSTEM: Fuel Pressure Control Vacuum Switching Valve Circuit

CIRCUIT DESCRIPTION





The Engine Control Module turns on a Vacuum Switching Valve (Vacuum Switching Valve) to draw the air into the diaphragm chamber of the pressure regulator if it detects that the temperature of the engine coolant is too high during engine starting. The air drawn into the chamber increases the fuel pressure to prevent fuel vapor lock at high engine temperature in order to help the engine start when it is warm. Fuel pressure control ends approximately 1 - 20 seconds after the engine is started.





DIAGNOSTIC PROCEDURE USING LEXUS HANDHELD TESTER
1. Connect the LEXUS hand-held tester and check operation of Fuel Pressure Control Vacuum Switching Valve.
- If Not OK proceed to step 2.
- If OK check and repair Fuel Pressure Regulator.
2. Check Fuel Pressure Control Vacuum Switching Valve.
- If OK proceed to step 3.
- If not OK replace Fuel Pressure 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 Fuel Pressure Control Vacuum Switching Valve.
- If OK proceed to step 2.
- If not OK replace Fuel Pressure Control Vacuum Switching Valve.
2. Check voltage between terminal FPU and body ground.
- If OK proceed to step 3.
- If not OK check and repair harness or connector.
3. Check Fuel Pressure Regulator.
- If OK check and replace Engine Control Module.
- If not OK repair or replace.