Home ReviewsRefund
Home/Lexus/IS/Lexus IS I (1999-2005)/Repair manual/Testing & Diagnostics/Engine Controls - Basic Diagnostic Procedures: Overview
Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Controls - Basic Diagnostic Procedures: Overview Lexus IS I

Testing & Diagnostics 11 illustrations ~2461 words

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

Scheme 1: Checking Fuel Pump Operation Using Scan Tool (GS300, GS430, IS300 & LS430)
Scheme 1: Checking Fuel Pump Operation Using Scan Tool (GS300, GS430, IS300 & LS430)
  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 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»(ref-134934-S28287544322002022100000). If fuel pump does not operate, check for defective fusible links/fuses. See «WIRING DIAGRAMS»(/lexus/is/i-1999-2005/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. 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»(ref-134934-S39429593102002022100000). 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»(ref-134934-S28287544322002022100000). If fuel pump does not operate, go to next step.
  4. Check for defective fuses/fusible links. See «WIRING DIAGRAMS»(/lexus/is/i-1999-2005/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. If fuses/fusible links are okay, check for defective fuel pump. See «CHECKING FUEL PUMP OPERATION BY APPLYING BATTERY VOLTAGE TO FUEL PUMP»(ref-134934-S39429593102002022100000). 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»(ref-134941) article. For testing of EFI main relay or fuel pump switch, see «SYSTEM & COMPONENT TESTING - LX470»(ref-134945) article.

Scheme 2

Scheme 2
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»(ref-134934-S28287544322002022100000) . If fuel pump does not operate, check for defective fusible links/fuses, wiring or EFI main relay. See «WIRING DIAGRAMS»(/lexus/is/i-1999-2005/remont/wiring-diagrams-engine-performance/#wiring-diagrams) article. 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»(ref-134934-S39429593102002022100000) . 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»(ref-134944) article.

Checking Fuel Pump Operation By Applying Battery Voltage To Fuel Pump

  1. On all models except RX300 and LX470, 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 5.
  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 5.
  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, using DVOM, measure resistance between fuel pump terminals No. 4 and 5. (Scheme 3) If resistance is.2-3 ohms, go to next step. If resistance is not.2-3 ohms, replace fuel pump. CAUTION: When applying battery voltage to fuel pump, DO NOT apply battery voltage for more than 10 seconds, or fuel pump may be damaged.
  5. Connect battery voltage to terminal No. 4, and ground to terminal No. 5 on fuel pump to activate fuel pump. (Scheme 4) DO NOT apply battery voltage to fuel pump for more than 10 seconds.
  6. 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»(ref-134934-S28287544322002022100000).
  7. If fuel pump fails to operate, replace fuel pump and/or lead wire to fuel pump (if equipped). See «FUEL SYSTEM»(ref-134951-S16927871712002022100000) in REMOVAL, OVERHAUL & INSTALLATION 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»(ref-134934-S36940904812002022100000) for additional testing information.

Scheme 3

Scheme 3
Scheme 3

Scheme 4

Scheme 4
Scheme 4

Scheme 5

Scheme 5: FUEL PRESSURE RELEASE
Scheme 5: FUEL PRESSURE RELEASE
  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 5) 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.

Scheme 6

Scheme 6: ES300 & RX300
Scheme 6: ES300 & RX300
  1. Ensure battery is fully charged. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-134934-S35033301942002022100000). Disconnect negative battery cable.
  2. Purchase a No. 1 fuel pipe Part No. (23801-20150) from parts department. No. 1 fuel pipe fits between fuel rails and fuel inlet pipe. (Scheme 6) Remove fuel pipe connector from end of NEW No. 1 fuel pipe. (Scheme 9)
  3. Remove fuel pipe clamp from No. 1 fuel pipe at fuel inlet pipe. (Scheme 6) Ensure area around No. 1 fuel pipe and fuel inlet pipe is clean.
  4. Depress both sides of retainer and pull No. 1 fuel pipe with disconnect fitting from fuel inlet pipe. (Scheme 7)
  5. Install Adapter (SST 09268-41250), hose and fuel pressure gauge from Fuel Pressure Gauge Set (SST 09268-41250) with fuel pipe connector between No. 1 fuel pipe and fuel inlet pipe. (Scheme 8) Ensure hose, No. 1 fuel pipe and fuel pipe connector are properly connected.
  6. Install negative battery cable. Connect scan tool to Data Link Connector (DLC) No. 3, located under left side of instrument panel. Turn ignition on. DO NOT start engine.
  7. Turn scan tool on. Select ACTIVE TEST MODE on scan tool. Using scan tool manufacturer's instructions, activate fuel pump and note fuel pressure. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ). NOTE: Fuel pump may also be activated by connecting battery voltage to specified terminals on fuel pump. (Scheme 4)
  8. If fuel pressure is within specification, go to next step. If fuel pressure exceeds specification, replace fuel pressure regulator mounted on fuel pump in fuel tank. See «FUEL SYSTEM»(ref-134951-S16927871712002022100000) in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is less than specified, check for leaking fuel hoses or connections, restricted fuel filter, defective fuel pump or defective fuel pressure regulator.
  9. Remove scan tool from DLC No. 3. Start engine and note fuel pressure with engine idling. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ). Shut engine off and note fuel pressure. Fuel pressure should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes. If fuel pressure is within specification and holds as specified, go to next step. If fuel pressure is not within specification or does not hold as specified, check for defective fuel pump, fuel injector or fuel pressure regulator.
  10. Release fuel pressure. Disconnect negative battery cable. Remove adapter, hose, fuel pressure gauge and fuel pipe connector.
  11. Install No. 1 fuel pipe on fuel inlet pipe. Pull on No. 1 fuel pipe to ensure fuel pipe is properly locked on fuel inlet pipe. Reinstall fuel pipe clamp until "click" sound is heard. Pull upward on fuel pipe clamp to ensure fuel pipe clamp is securely locked on fuel inlet pipe. Install negative battery cable. Check for fuel leaks by using scan tool to energize fuel pump.

Scheme 7

Scheme 7
Scheme 7

Scheme 8

Scheme 8
Scheme 8

Scheme 9

Scheme 9
Scheme 9

Scheme 10

Scheme 10: GS300 & IS300
Scheme 10: GS300 & IS300
  1. Ensure battery is fully charged. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-134934-S35033301942002022100000). Disconnect negative battery cable.
  2. Note location of fuel inlet hose on fuel pipe support. (Scheme 10) Remove union bolt with gaskets, and disconnect fuel inlet hose from fuel pipe support.
  3. Using Adapter (SST 09268-41190), Union (SST 90405-06167) and fuel pressure gauge from Fuel Pressure Gauge Set (SST 09268-45014) with gaskets, install fuel pressure gauge and fuel inlet hose. (Scheme 10) Tighten adapter to 21 ft. lbs. (29 N.m). Install negative battery cable.
  4. 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 and note fuel pressure. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ). NOTE: Fuel pump may also be activated by connecting battery voltage to specified terminals on fuel pump. (Scheme 4)
  5. If fuel pressure is within specification, go to next step. If fuel pressure exceeds specification, replace fuel pressure regulator mounted on fuel pump in fuel tank. See «FUEL SYSTEM»(ref-134951-S16927871712002022100000) in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is less than specified, check for leaking fuel hoses or connections, restricted fuel filter, defective fuel pump or fuel pressure regulator.
  6. Remove scan tool from DLC No. 3. Start engine and note fuel pressure with engine idling. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ).
  7. Shut engine off and note fuel pressure. Fuel pressure should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes. If fuel pressure holds as specified, go to next step. If fuel pressure does not hold as specified, check for defective fuel pump, fuel injector or fuel pressure regulator.
  8. Release fuel pressure. Disconnect negative battery cable. Remove adapter, union and fuel pressure gauge. Reinstall fuel inlet hose on fuel pipe support using NEW gasket. Tighten union bolt to 21 ft. lbs. (29 N.m). Install negative battery cable. Check for fuel leaks by using scan tool to energize fuel pump.

Scheme 11

Scheme 11: GS430, LS430 & SC430
Scheme 11: GS430, LS430 & SC430
  1. Ensure battery is fully charged. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-134934-S35033301942002022100000). Disconnect negative battery cable.
  2. Remove cover located on top of engine to gain access to fuel pressure pulsation dampers. Fuel pressure pulsation dampers are located at firewall end of each fuel rail. (Scheme 11) Remove necessary components for access to fuel pressure pulsation damper on passenger's side fuel rail.
  3. Remove fuel pressure pulsation damper with gaskets from rear of passenger's side fuel rail. Using Adapter (SST 09268-41190), Union (SST 90405-06167) and fuel pressure gauge from Fuel Pressure Gauge Set (SST 09268-45014) with gaskets, install fuel pressure gauge and rear fuel pipe on rear of passenger's side fuel rail. (Scheme 11) Tighten adapter to 29 ft. lbs. (39 N.m). Install negative battery cable.
  4. 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 and note fuel pressure. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ). NOTE: Fuel pump may also be activated by connecting battery voltage to specified terminals on fuel pump. (Scheme 4)
  5. If fuel pressure is within specification, go to next step. If fuel pressure exceeds specification, replace fuel pressure regulator mounted on fuel pump in fuel tank. See «FUEL SYSTEM»(ref-134951-S16927871712002022100000) in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is less than specified, check for leaking fuel hoses or connections, restricted fuel filter, defective fuel pump or fuel pressure regulator.
  6. Remove scan tool from DLC No. 3. Start engine and note fuel pressure with engine idling. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm 2 ).
  7. Shut engine off and note fuel pressure. Fuel pressure should remain at least 21 psi (1.5 kg/cm 2 ) for a minimum of 5 minutes. If fuel pressure holds as specified, go to next step. If fuel pressure does not hold as specified, check for defective fuel pump, fuel injector or fuel pressure regulator.
  8. Release fuel pressure. Disconnect negative battery cable. Remove adapter, union and fuel pressure gauge. Using NEW gaskets, install rear fuel pipe and fuel pressure pulsation damper on passenger's side fuel rail. Tighten fuel pressure pulsation damper to 29 ft. lbs. (39 N.m). Install negative battery cable. Check for fuel leaks by using scan tool to energize fuel pump.

More articles — Engine Controls - Basic Diagnostic Procedures