Engine Controls - Basic Diagnostic Procedures: Overview Lexus SC II

FUEL PUMP OPERATION

Note. Information for ES300 is not available from manufacturer.

Note. Electric fuel pump is located in fuel tank. Electric fuel pump operation may be checked by using scan tool or by applying battery voltage to electric fuel pump with electric fuel pump installed in fuel tank.

Scheme 1

1. Connect scan tool to Data Link Connector (DLC) No. 3, located under left side of instrument panel. Turn ignition on. DO NOT start engine.
2. Turn scan tool on. Select ACTIVE TEST mode on scan tool. Using scan tool manufacturer's instructions, activate fuel pump. On GS300, GX470 and IS300, listen for fuel pump operating sound and check that screw at center of fuel pressure pulsation damper moves upward due to fuel pressure. (Scheme 1) Fuel pulsation damper is located at firewall end of fuel rail. On all other models, listen for fuel pump operating sound and feel for fuel pressure in fuel inlet hose.
3. On all models, turn ignition off. Remove scan tool. If fuel pump operates, check fuel pressure. See «FUEL PRESSURE». If fuel pump does not operate, check for defective fusible links/fuses. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If fusible links/fuses are okay, go to next step.
4. Check for defective fuel pump. See «CHECKING FUEL PUMP OPERATION BY APPLYING BATTERY VOLTAGE TO FUEL PUMP». Replace fuel pump as necessary and retest. If fuel pump operates, check fuel pump control circuit. See FUEL DELIVERY under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

Checking Fuel Pump Operation Using Scan Tool (LX470)

1. Connect scan tool to Data Link Connector (DLC) No. 3, located under left side of instrument panel. Turn ignition on. DO NOT start engine. Turn scan tool on. Select ACTIVE TEST MODE on scan tool. Using scan tool manufacturer's instructions, activate fuel pump.
2. Remove engine cover, above intake manifold. Engine cover must be removed for access to fuel pressure pulsation damper located at firewall end of driver's side fuel rail. (Scheme 2)
3. Listen for operating sound at fuel pump and check that screw at center of fuel pressure pulsation damper moves upward due to fuel pressure. (Scheme 2) If fuel pump operates, check fuel pressure. See «FUEL PRESSURE». If fuel pump does not operate, go to next step.
4. Check for defective fuses/fusible links. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If fuses/fusible links are okay, check for defective fuel pump. See «CHECKING FUEL PUMP OPERATION BY APPLYING BATTERY VOLTAGE TO FUEL PUMP». Replace fuel pump as necessary. If fuel pump operates, go to next step.
5. EFI main relay, fuel pump Electronic Control Unit (ECU) or fuel pump switch may be defective, or fuel pump switch may need to be reset. If problem exists with fuel pump ECU or wiring circuit, a Diagnostic Trouble Code (DTC) P1200 should be stored in Engine Control Module (ECM). Retrieve DTCs and perform appropriate diagnostic test. See «SELF-DIAGNOSTICS - LX470» article. For testing of EFI main relay or fuel pump switch, see «SYSTEM & COMPONENT TESTING - LX470» article.

Scheme 2

Checking Fuel Pump Operation Using Scan Tool (RX300)

1. Connect scan tool to Data Link Connector (DLC) No. 3, located under left side of instrument panel. Turn ignition on. DO NOT start engine. Turn scan tool on. Select ACTIVE TEST mode on scan tool. Using scan tool manufacturer's instructions, activate fuel pump.
2. Listen for fuel pump operating sound and feel for fuel pressure in inlet line from fuel filter. Turn ignition off. Remove scan tool. If fuel pump operates, check fuel pressure. See «FUEL PRESSURE». If fuel pump does not operate, check for defective fusible links/fuses, wiring or EFI main relay. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If fusible links/fuses, wiring and EFI main relay are okay, go to next step.
3. Check for defective fuel pump. See «CHECKING FUEL PUMP OPERATION BY APPLYING BATTERY VOLTAGE TO FUEL PUMP». Replace fuel pump as necessary and retest. If fuel pump operates, check fuel pump control circuit. See FUEL DELIVERY under FUEL SYSTEM in «SYSTEM & COMPONENT TESTING - ES300 & RX300» article.

Checking Fuel Pump Operation By Applying Battery Voltage To Fuel Pump

1. On all models except LX470 and RX300, remove rear seat cushion. Remove cover plate on floor panel for access to electrical connector for fuel pump. Disconnect electrical connector for fuel pump. This is electrical connector for fuel pump and fuel gauge sending unit and is located on top of fuel tank, near fuel pump. Go to step 4.
2. On LX470, remove second seats, rear door scuff plates, step plates, second seat lock covers, rear carpet and cover plate on floor panel for access to electrical connector for fuel pump. Disconnect electrical connector for fuel pump. This is electrical connector for fuel pump and fuel gauge sending unit and is located on top of fuel tank, near fuel pump. Go to step 4.
3. On RX300, remove driver's side rear seat. Remove carpet and cover plate on floor panel for access to electrical connector for fuel pump. Disconnect electrical connector for fuel pump. This is electrical connector for fuel pump and fuel gauge sending unit and is located on top of fuel tank, near fuel pump. Go to next step.
4. Connect battery voltage to terminal No. 4, and ground to terminal No. 5 on fuel pump to activate fuel pump. (Scheme 3) DO NOT apply battery voltage to fuel pump for more than 10 seconds.
5. Listen for fuel pump operating sound. Disconnect battery voltage from fuel pump. If fuel pump operates, check fuel pressure after reinstalling components. See «FUEL PRESSURE».
6. If fuel pump fails to operate, replace fuel pump and/or lead wire to fuel pump (if equipped). On all models except GX470, see «FUEL SYSTEM» in REMOVAL & INSTALLATION - EXCEPT GX470 article. On GX470, see «FUEL SYSTEM» in REMOVAL & INSTALLATION - GX470 article. If fuel pump will not operate while trying to start engine, see appropriate CHECKING FUEL PUMP OPERATION USING SCAN TOOL under «FUEL PUMP OPERATION» for additional testing information.

Scheme 3

Scheme 4

1. On all models except RX300 and LX470, remove rear seat cushion and cover plate on floor panel for access to electrical connector for fuel pump. Disconnect electrical connector for fuel pump. This is electrical connector for fuel pump and fuel gauge sending unit. Go to step 4.
2. On LX470, disconnect electrical connector for fuel pump. (Scheme 4) This is electrical connector for fuel pump and fuel gauge sending unit. Go to step 4.
3. On RX300, remove driver's side rear seat. Remove carpet and cover plate on floor panel for access to electrical connector for fuel pump. Disconnect electrical connector for fuel pump. This is electrical connector for fuel pump and fuel gauge sending unit and is located on top of fuel tank, near fuel pump. Go to next step.
4. On all models, start engine and allow engine to idle until engine stalls. Turn ignition off. Reinstall electrical connector for fuel pump and any removed components.
5. Disconnect negative battery cable. Place suitable container under fuel line connection. Cover fuel line connection with shop towel. Slowly loosen fuel line connection, allowing any fuel pressure to be released. Once fuel pressure is released, fuel system components may be serviced.

See also:
• COMPUTER RELEARN PROCEDURES - LEXUS
• THEORY & OPERATION