Engine Controls - Basic Testing: Overview

Engine Controls - Basic Testing: Overview Lexus GS II

Checking Fuel Pump Operation (Using Lexus Scan Tool)

Connect Lexus scan tool to Data Link Connector (DLC) No. 3. (Scheme 1) Turn ignition on. Turn scan tool on. DO NOT start engine.
Select ACTIVE TEST mode on scan tool. Using Lexus scan tool manufacturer's instructions, activate electric fuel pump. On all models except GS300 and SC300, fuel pump is operating if fuel pump operating sound can be heard or pulsations can be felt in fuel line near fuel filter. On GS300 and SC300, check that fuel pressure pulsation damper screw rises when fuel pump operates. (Scheme 2)
If fuel pump operates, check fuel pressure. See «FUEL PRESSURE»(ref-22506-S17436168932001010300000). If fuel pump does not operate, check for a defective EFI main relay, fuel pump, fusible link, ECM or poor wiring connections. Check for a defective AM2 (30-amp) fuse located in engine compartment fuel relay box, left side of engine compartment. Check for a defective IGN (5-amp) fuse located in instrument panel fuel/relay box, at bottom left of steering column.
If all components are okay and fuel pump still does not operate, check for defective fuel pump or fuel pump ground. See appropriate wiring diagram in WIRING DIAGRAMS article.

On ES300, GS300 and GS400, remove rear seat cushion. Remove fuel pump access cover. Remove floor service hole cover. Disconnect 5-pin connector from fuel pump and sending unit assembly. Connect a fused jumper wire between fuel pump connector terminal No. 4 and battery voltage. (Scheme 3)
Connect one end of second fused jumper wire to fuel pump connector terminal No. 5 first and then connect other end of fused jumper wire to ground. Ensure not to apply battery voltage to fuel pump for more than 10 seconds.
On LS400, SC300 and SC400, remove trunk floor mat. Remove trunk trim cover from behind rear seat in luggage compartment. Disconnect 2-pin fuel pump connector (NOT the sending unit connector) located behind rear speaker. Connect a fused jumper wire between fuel pump connector terminal No. 1 and battery voltage. (Scheme 4)
Connect one end of second jumper wire to fuel pump connector terminal No. 2 first and then connect other end of fused jumper wire to ground. Ensure not to apply battery voltage to fuel pump for more than 10 seconds.
On all models except GS300, fuel pump is operating if fuel pump operating sound can be heard or pulsations can be felt in fuel line near fuel filter. On GS300, check that fuel pressure pulsation damper screw rises when fuel pump operates. (Scheme 2)