Engine Controls - System & Component Testing: Diagnosis Lexus LX J100

Circuit Description

When ignition switch is turned on, 9-14 volts is applied to the terminal IGSW at ECM and the main relay control circuit in the ECM sends a signal to terminal M-REL at ECM switching EFI main relay on.

Diagnosis & Repair

1. Access ECM behind glove box. Turn ignition on. Backprobing connector, connect DVOM negative lead to terminal No. 17 (Brown wire) at ECM E7 connector and positive lead to terminal No. 16 (Black/Yellow wire) at ECM E10 connector. (Scheme 44) If 9-14 volts is present, ECM power circuit is okay. Diagnose by symptom. See 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 E7 connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, go to next step.
3. Measure voltage between chassis ground and terminal No. 9 (Black/Red wire) at ECM E10 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 on driver's side of vehicle, behind left kick panel.
4. If fuse is blown, repair cause of blown fuse. If fuse is okay, check ignition switch. See 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 10 (Black/White wire) at ECM E10 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-2786-S21698068102000041300000) under MOTORS & RELAYS. If EFI main relay is okay, check circuit between chassis ground and terminal No. 10 at ECM E10 connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, repair circuit between battery and EFI fuse.

Scheme 44

When engine is being cranked, intake air flow is slow, so fuel vaporization is poor. A rich mixture is necessary to achieve good startability. 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 45) 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 TROUBLE SHOOTING - NO CODES article.
3. Check for open in wiring harness between ECM and starter relay. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.

Scheme 45

Diagnosis & Repair (Using OBD-II Scan Tool)

1. Access ECM behind glove box. Backprobing ECM connector, measure voltage between ground and terminal No. 17 (Black/Red wire) at ECM E9 connector. (Scheme 44)
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 TROUBLE SHOOTING - NO CODES article.
3. Check for open in wiring harness between ECM and starter relay. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.

Fuel EVAP System Test

Note. Manufacturer provides testing information for testing airtightness of fuel tank and components along with testing of charcoal canister and fuel EVAP system.

Scheme 46

Scheme 47

1. Inspect all lines and connections for sharp bends or damage. Inspect fuel tank for damage, cracks 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 purge vacuum hose for EVAP system near charcoal canister in engine compartment. see scheme 21
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 No. 3. (Scheme 45) 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 electrical connector. EVAP VSV is located on driver's side center of intake manifold below intake manifold cover on top of engine and contains Black 2-Pin electrical connector with Blue/Black and Black/Yellow wires. see scheme 21 Using jumper wires, connect battery voltage and ground to electrical terminals on EVAP VSV to operate EVAP VSV. Start engine. Go to next step.
6. Check vacuum reading on vacuum gauge with engine idling. Vacuum should be.368-19.713 in Hg. for more than 5 seconds. If vacuum is within specification, go to next step. If vacuum reading 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-2786-S38487815052000041300000).
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. Install hose crimper on air drain hose near charcoal canister. (Scheme 46) Charcoal canister is located in driver's side of engine compartment. see scheme 21
9. Apply 13.5-15.5 in. H 2 O of pressure to EVAP service port. After 2 minutes of applying the pressure, the pressure should be 7.7-8.8 in. H 2 O. 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-2786-S38487815052000041300000).
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. 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.
12. Apply.26 psi (.018 kg/cm 2 ) air pressure to port "A" while holding port "B" closed. (Scheme 47) Ensure air flows freely from port "D".
13. Apply.26 psi (.018 kg/cm 2 ) air pressure to port "A" while holding ports "B" and "D" closed. (Scheme 47) Ensure no air flows from port "C".
14. Using vacuum pump, apply 1.01 in. Hg of vacuum to port "B". Ensure vacuum does not decrease when port "C" is closed, and that vacuum decreases when port "C" is opened.
15. While holding port "C" closed, use vacuum pump to apply.39 in. Hg of vacuum to port "A". Ensure air flows into port "B". Replace charcoal canister if defective.
16. 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 and vapor pressure sensor Vacuum Switching Valve (VSV). See «EVAP VACUUM SWITCHING VALVE»(ref-2786-S38487815052000041300000), «VAPOR PRESSURE SENSOR»(ref-2786-S31709732522000041300000) and «VAPOR PRESSURE SENSOR VACUUM SWITCHING VALVE»(ref-2786-S32049558492000041300000).