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Engine Controls - System & Component Testing: Diagnosis Lexus ES XV30 facelift

Testing & Diagnostics 10 illustrations ~2623 words

Circuit Description

When ignition switch is turned on, 9-14 volts is applied to the terminal IGSW at ECM main relay control circuit, sending a signal to terminal MREL at ECM, which then switches EFI main relay on. When ignition is turned off, ECM will keep EFI main relay on for 2 seconds or less in order to reset Idle Air Control (IAC) valve.

Diagnostic Procedure (ES300)

  1. Access ECM behind glove box. Turn ignition on. Backprobing connector, connect DVOM negative lead to terminal No. 28 (Brown wire) at ECM E10 connector and positive lead to terminal No. 1 (Black/Red wire) at ECM E6 connector. (Scheme 190) If 9-14 volts are present, ECM power circuit is okay. Diagnose by symptom. See «SYMPTOMS»(ref-151782-S30294375292003010800000) in TROUBLE SHOOTING - NO CODES article. If 9-14 volts are not present, go to next step.
  2. Check for an open circuit in Brown wire between ground and terminal No. 28 at ECM E10 connector. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, go to next step.
  3. Measure voltage between terminal No. 28 (Brown wire) at ECM E10 connector and terminal No. 9 (Black/Orange wire) at ECM E6 connector. If 9-14 volts is present, go to step 5. If 9-14 volts is not present, check AM2 fuse in engine compartment junction box.
  4. If fuse is blown, repair cause of blown fuse. If fuse is okay, check ignition switch. See «STEERING COLUMN SWITCHES»(ref-152427) article in ACCESSORIES & EQUIPMENT. Replace ignition switch as necessary and retest. If ignition switch is okay, repair open circuit between battery and ignition switch, or between ignition switch and ECM.
  5. Turn ignition on. Measure voltage between terminal No. 28 (Brown wire) at ECM E10 connector and terminal No. 8 (Black/White wire) at ECM E6 connector. If 9-14 volts are not present, replace ECM. If 9-14 volts are present, check EFI fuse located in engine compartment fuse/relay box. If fuse is okay, go to next step. If EFI fuse is blown, repair cause of blown fuse.
  6. Check EFI main relay located in engine compartment fuse/relay box. See «RELAYS»(ref-151786-S31514697312003010800000) under RELAYS & SOLENOIDS. If EFI main relay is okay, check circuit between terminal No. 28 (Brown wire) at ECM E10 connector and terminal No. 8 (Black/White wire) at ECM E6 connector. See appropriate WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, repair circuit between battery and EFI fuse.

Scheme 190

Scheme 190
Scheme 190

Diagnostic Procedure (RX300)

  1. Access ECM behind glove box. Turn ignition on. Backprobing connector, connect DVOM negative lead to terminal No. 17 (Brown wire) at ECM E8 connector and positive lead to terminal No. 16 (Black/Red wire) at ECM E5 connector. (Scheme 191) If 9-14 volts is present, ECM power circuit is okay. Diagnose by symptom. See «SYMPTOMS»(ref-151782-S30294375292003010800000) in TROUBLE SHOOTING - NO CODES article. If 9-14 volts is not present, go to next step.
  2. Check for an open circuit in Brown wire between ground and terminal 17 at ECM E8 connector. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, go to next step.
  3. Measure voltage between chassis ground and terminal No. 2 (Black/Orange wire) at ECM E5 connector. If 9-14 volts is present, go to step 5. If 9-14 volts is not present, check IGN fuse in instrument panel junction box under left side of instrument panel.
  4. If fuse is blown, repair cause of blown fuse. If fuse is okay, check ignition switch. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. Replace ignition switch as necessary and retest. If ignition switch is okay, repair open circuit between battery and ignition switch, or between ignition switch and ECM.
  5. Turn ignition on. Measure voltage between chassis ground and terminal No. 8 (Black/White wire) at ECM E5 connector. If 9-14 volts is not present, replace ECM. If 9-14 volts is present, check EFI fuse located in engine compartment fuse/relay box at left front of engine compartment. If fuse is okay, go to next step. If EFI fuse is blown, repair cause of blown fuse.
  6. Check EFI main relay located in engine compartment fuse/relay box at left front of engine compartment. See «RELAYS»(ref-151786-S31514697312003010800000) under RELAYS & SOLENOIDS. If EFI main relay is okay, check circuit between chassis ground and terminal No. 8 at ECM E5 connector. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If circuit is okay, repair circuit between battery and EFI fuse.

Scheme 191

Scheme 191
Scheme 191

When engine is being cranked, intake air flow is slow, so fuel vaporization is poor. A rich mixture is necessary to achieve good starting performance. While engine is being cranked, 9-14 volts is supplied to ECM terminal STA. Starter signal is mainly used to increase fuel injection pulse for starting injection control and after-start injection control.

Note. The following test assumes starter cranks normally with ignition in START position. If starter does not crank normally, check and repair starter circuit before continuing with this test.

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. (Scheme 192)and (Scheme 193). Turn scan tool on. Turn ignition on. Using scan tool, read STA signal with ignition on and then while cranking starter.
  2. With ignition on, STA signal should be off. With ignition switch in START position, STA signal should be on. If STA signal is not as specified, go to next step. If STA signal is as specified, no problem is indicated at this time. Diagnose by symptom. See «SYMPTOMS»(ref-151782-S30294375292003010800000) in TROUBLE SHOOTING - NO CODES article.
  3. Check for open in wiring harness between ECM and starter relay. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, replace ECM and retest.

Scheme 192

Scheme 192
Scheme 192

Scheme 193

Scheme 193
Scheme 193

Diagnosis & Repair (Using OBD-II Scan Tool) - ES300

  1. Access ECM harness connectors behind glove box. Backprobing ECM harness connector, measure voltage between ground and terminal No. 7 (Gray wire) STA at ECM E7 connector. (Scheme 190)
  2. Turn ignition switch to START position. With starter being cranked, voltage should be 6 volts or more. If voltage is not as specified, go to next step. If voltage is as specified, no problem is indicated at this time. Diagnose by symptom. See «SYMPTOMS»(ref-151782-S30294375292003010800000) in TROUBLE SHOOTING - NO CODES article.
  3. Check for open in wiring harness between ECM and starter relay. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, replace ECM and retest.

Diagnosis & Repair (Using OBD-II Scan Tool) - RX300

  1. Access ECM harness connectors behind glove box. Backprobing ECM harness connector, measure voltage between ground and terminal No. 9 (Black/Yellow wire) STA at ECM E9 connector. (Scheme 191)
  2. Turn ignition switch to START position. With starter being cranked, voltage should be 6 volts or more. If voltage is not as specified, go to next step. If voltage is as specified, no problem is indicated at this time. Diagnose by symptom. See «SYMPTOMS»(ref-151782-S30294375292003010800000) in TROUBLE SHOOTING - NO CODES article.
  3. Check for open in wiring harness between ECM and starter relay. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, replace ECM and retest.

Testing Air/Fuel (A/F) HTR Relay, Circuit Opening Relay, EFI Main Relay Or Starter Relay

  1. Remove relay to be tested. On RX300, circuit opening relay (CIR OPN) may be located in fuse/relay box on left side of engine compartment or relay box under left side of instrument panel. On ES300, circuit opening relay is located in fuse/relay box on left side of engine compartment. On all models, A/F HTR relay, EFI main relay and starter relay are located in the main fuse/relay box on left side of engine compartment.
  2. Check for continuity between relay terminals No. 1 and 2. (Scheme 194)or (Scheme 195). Continuity should exist. Check for continuity between relay terminals No. 3 and 5. Continuity should not exist.
  3. Using jumper wires, apply battery voltage across relay terminals No. 1 and 2. Check for continuity between relay terminals No. 3 and 5 with relay energized. Continuity should exist. If continuity is not as specified, replace relay.

Scheme 194

Scheme 194
Scheme 194

Scheme 195

Scheme 195
Scheme 195

Fuel EVAP System Test

  1. Inspect all EVAP system lines and connections for sharp bends or damage. see scheme 37or see scheme 38. Fuel inlet pipe may also be referred to as fuel filler pipe. Inspect fuel inlet pipe for cracks, damage or fuel leakage. Inspect fuel tank cap for cracks or deformed gasket. Replace components if defective or damaged.
  2. Start engine and warm engine to normal operating temperature. Shut engine off. Connect vacuum gauge from EVAP system test kit to EVAP service port. EVAP service port is located in engine compartment (under air filter housing), in the purge vacuum hose for EVAP system. see scheme 37or see scheme 38.
  3. EVAP Vacuum Switching Valve (VSV) must be operated. If scan tool is available, go to next step. If scan tool is not available, go to step 5.
  4. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 192)or (Scheme 193). Start engine. Turn scan tool on. Select ACTIVE TEST MODE on scan tool. Using scan tool manufacturer's instructions, activate EVAP VSV. Go to step 6.
  5. Disconnect EVAP VSV connector. EVAP VSV is mounted on air intake chamber and contains a Blue 2-pin electrical connector. see scheme 11 Using jumper wires, connect battery voltage and ground to EVAP VSV terminals. Start engine. Go to next step.
  6. Check vacuum reading on vacuum gauge with engine idling. Vacuum should be.368-19.713 in. Hg (1.24-66.4 kPa) for more than 5 seconds. If vacuum is within specification, go to next step. If vacuum is not within specification, check for loose or restricted vacuum hose to EVAP service port, or for malfunctioning EVAP VSV. To check EVAP VSV operation, see «EVAP VACUUM SWITCHING VALVE»(ref-151786-S33307779722003010800000).
  7. Shut engine off. If using scan tool to operate EVAP VSV, stop operation of EVAP VSV. Remove scan tool. Go to next step. If connecting battery voltage to EVAP VSV to operate EVAP VSV, disconnect jumper wires and reconnect electrical connector on EVAP VSV. Go to next step.
  8. Disconnect vacuum gauge from EVAP service port. Connect pressure gauge to EVAP service port. Locate charcoal canister under rear of vehicle, near fuel tank. (Scheme 196)or (Scheme 197). Install hose crimper on charcoal canister air drain hose. Air hose may be marked with a Yellow line indicating area to be crimped at.
  9. Apply 13.5-15.5 in.H2O of pressure to EVAP service port. After 2 minutes of applying the pressure, the pressure should be 7.7-8.8 in.H20. If pressure is within specification, remove hose crimper and go to next step. If pressure cannot be maintained, remove hose crimper and check for disconnected vacuum hose between EVAP VSV, charcoal canister and fuel tank. If vacuum hose is properly installed on EVAP VSV, charcoal canister and fuel tank, check for stuck open EVAP VSV. To check EVAP VSV operation, see «EVAP VACUUM SWITCHING VALVE»(ref-151786-S33307779722003010800000).
  10. With pressure still applied at EVAP service port, remove fuel tank cap and note pressure reading. Pressure should decrease when fuel tank cap is removed. If pressure decreases when fuel tank cap is removed, remove pressure gauge and go to next step. If pressure does not decrease when fuel tank cap is removed, remove pressure gauge and check for restricted vacuum hose between EVAP service port, charcoal canister and fuel tank. Repair or replace vacuum hose as necessary.
  11. To check airtightness of fuel tank and fuel inlet pipe, disconnect EVAP line hose from charcoal canister. (Scheme 196)or (Scheme 197). Apply.58 psi (.040 kg/cm 2 ) air pressure to EVAP line hose so pressure inside the fuel tank is.58 psi (.040 kg/cm 2 ). Check that pressure inside fuel tank holds steady for one minute.
  12. If pressure inside fuel tank holds steady for one minute, reinstall EVAP line hose on charcoal canister. Go to next step. If pressure inside fuel tank will not hold steady for one minute, check for leaking hoses or pipes at fuel tank and fuel inlet pipe, or for leaks at fuel tank or installed components on fuel tank. If no leaks exist, replace fuel tank and fuel inlet pipe. Reinstall EVAP line hose on charcoal canister. Go to next step. NOTE: Overfill check valve may also be referred to as fill check valve. Cut-off valve may also be referred to as fuel cut-off valve.
  13. To check overfill check valve and cut-off valve, disconnect purge line hose, air drain hose and EVAP line hose from charcoal canister. Install cap on air drain hose port. (Scheme 196)or (Scheme 197).
  14. Apply.58 psi (.040 kg/cm 2 ) air pressure to purge line hose fitting on charcoal canister. (Scheme 196)or (Scheme 197). Ensure air flows from EVAP line hose when air pressure is applied to purge line hose fitting on charcoal canister. If fuel tank is full of fuel, air may not flow from EVAP line hose, as overfill check valve may be closed. Ensure fuel tank is not full of fuel when checking for airflow at EVAP line hose.
  15. If air flows from EVAP line hose, go to next step. If air does not flow from EVAP line hose, check for restrictions in EVAP line hose and vent line hose. If any hose is restricted, replace hose and recheck operation. If hoses are not restricted, replace overfill check valve and cut-off valve located on top of fuel tank. (Scheme 196)or (Scheme 197).
  16. Reinstall purge line hose, air drain hose and EVAP line hose on charcoal canister. To check air inlet line, disconnect air inlet line hose from charcoal canister. (Scheme 196)or (Scheme 197). Apply air pressure to air inlet line hose. Air should flow through air inlet line hose. If air flows through air inlet line hose, go to next step. If air does not flow through air inlet line hose, check for restricted air inlet line hose or air inlet line.
  17. Disconnect necessary electrical connectors and components for removal of charcoal canister. Disconnect purge line hose, EVAP line hose and air inlet line hose from charcoal canister.
  18. Push connector on vent line hose toward charcoal canister and pinch both sides of retainer on connector, and then disconnect vent line hose with connector from charcoal canister. (Scheme 198)
  19. Remove charcoal canister and vapor pressure sensor retaining bolts. Remove charcoal canister. Inspect charcoal canister for cracks or damage at all hose fittings. If charcoal canister is okay, go to next step. If charcoal canister is defective, replace charcoal canister.
  20. To check charcoal canister, install cap on vent port on charcoal canister. (Scheme 199) Apply.26 psi (.018 kg/cm 2 ) air pressure to EVAP port while holding purge port closed. Ensure air flows freely from air drain port.
  21. Apply.26 psi (.018 kg/cm 2 ) air pressure to EVAP port while holding air drain hose and purge port closed. (Scheme 199) Ensure no air flows from air inlet port.
  22. Using vacuum pump, apply 1.01 in. Hg of vacuum to purge port. (Scheme 199) Ensure vacuum does not decrease when air inlet port is closed, and that vacuum decreases when air inlet port is opened.
  23. While holding air inlet port closed, use vacuum pump to apply 1.01 in. Hg of vacuum to EVAP port. (Scheme 199) Ensure air flows into purge port. Remove cap from vent port. Replace charcoal canister if defective.
  24. Reinstall charcoal canister. If fuel EVAP system operates properly, it may be necessary to check operation of EVAP Vacuum Switching Valve (VSV), vapor pressure sensor, pressure switching valve and canister closed valve VSV. See «EVAP VACUUM SWITCHING VALVE»(ref-151786-S33307779722003010800000), «VAPOR PRESSURE SENSOR CIRCUIT»(ref-151786-S18611215822003010800000), «PRESSURE SWITCHING VALVE VACUUM SWITCHING VALVE»(ref-151786-S22646217142003010800000) and «CANISTER CLOSED VALVE VACUUM SWITCHING VALVE»(ref-151786-S31982637932003010800000).

Scheme 196

Scheme 196
Scheme 196

Scheme 197

Scheme 197
Scheme 197

Scheme 198

Scheme 198
Scheme 198

Scheme 199

Scheme 199
Scheme 199

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