Engine Controls - System/component Tests Lexus ES V20

INTRODUCTION

Before testing separate components or systems, perform procedures in BASIC TESTING article. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in TESTS W/CODES article.

TESTING - PRELIMINARY INFORMATION

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

1. NEUTRAL START SWITCH CIRCUIT chart.
2. ECU POWER SOURCE CIRCUIT chart.
3. BACK-UP POWER SOURCE CIRCUIT chart.
4. INJECTOR CIRCUIT chart.
5. COLD START INJECTOR CIRCUIT chart.
6. IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart.
7. FUEL SYSTEM CIRCUIT chart.
8. FUEL PRESSURE CONTROL VACUUM SWITCHING VALVE (VSV) CIRCUIT chart.
9. TERMINAL TE1 & TE2 CIRCUIT DIAGNOSIS chart.
10. A/C COMPRESSOR CIRCUIT chart.

Refer to the following transmission diagnostic charts

1. MAIN THROTTLE POSITION SENSOR CIRCUIT chart.
2. NEUTRAL START SWITCH CIRCUIT chart.
3. STOPLIGHT CIRCUIT chart.
4. PATTERN SELECT SWITCH CIRCUIT chart.
5. O/D SWITCH & O/D OFF INDICATOR LIGHT CIRCUIT chart.
6. O/D CANCEL SIGNAL CIRCUIT chart.
7. DIAGNOSIS CIRCUIT chart.
8. CHECK CONNECTOR CIRCUIT chart.

COMPUTERIZED ENGINE CONTROLS

Scheme 44

Scheme 45

1. Ensure ignition is off. Disconnect connectors from ECU. Remove locks so ECU connector can be easily backprobed. (Scheme 45) Reconnect ECU connectors.
2. Turn ignition on. Using a DVOM, measure voltage between ECU terminals B1 and E1. (Scheme 44) Measure voltage between terminals B and E1. Battery voltage should be present.
3. If battery voltage is not present, ensure wire harness is not open or shorted. If wire harness is okay, replace ECU.

Scheme 46

1. Turn ignition off. Disconnect the airflow meter connector. Using a DVOM, measure resistance between the appropriate airflow meter terminals. (Scheme 46) For resistance specifications, refer to the «AIRFLOW METER RESISTANCE»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. AIRFLOW METER RESISTANCE Terminals Ohms °F (°C) VS & E2 200-600 N/A VC & E2 200-400 N/A THA & E2 10,000-20,000 -4 (-20) THA & E2 4000-7000 32 (0) THA & E2 2000-3000 68 (20) THA & E2 900-1300 104 (40) THA & E2 400-700 140 (60) FC & E1 Infinity N/A
2. Using a DVOM, measure resistance between airflow meter terminals while moving airflow measuring plate inside airflow meter. For specifications, see «AIRFLOW METER MEASURING PLATE RESISTANCE»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. (Scheme 46)

AIRFLOW METER MEASURING PLATE RESISTANCE

CLUTCH START SWITCH

1. Ensure clutch pedal height is correct. Pedal height is measured from floorboard (carpet removed) to face of pedal. Pedal height should be 7.52-7.91" (191-201 mm).
2. Clutch pedal free play should be .20-.59" (5.1-15 mm). Push rod play at top of clutch pedal should be .039-.197" (1-5 mm). Adjust pedal height, pedal free play and push rod play as necessary.
3. Disconnect clutch switch connector. Using a DVOM, check for continuity when switch is depressed. There should not be continuity when switch is released. If continuity is not as specified, replace clutch switch.

NEUTRAL START SWITCH

Neutral start switch is located on side of transaxle. Turn ignition off. Disconnect neutral start switch connector. (Scheme 47) Using a DVOM, check for continuity between terminals specified in the NEUTRAL START SWITCH CONTINUITY table. If continuity is not as specified, replace neutral start switch.

NEUTRAL START SWITCH CONTINUITY

Scheme 47

THROTTLE POSITION SENSOR (TPS)

Turn ignition off. Disconnect TPS connector. (Scheme 48) Using a DVOM, measure resistance between specified TPS terminals in the TPS SPECIFICATIONS table.

TPS SPECIFICATIONS

Scheme 48

Scheme 49

1. Turn ignition off. Remove relay from vehicle. Using a DVOM, check for continuity between relay terminals STA and E1. (Scheme 49) Check for continuity between terminals B and FC. Ensure there is no continuity between B and FP. If continuity is not as specified, replace relay.
2. Apply battery voltage between terminals STA and E1. Using a DVOM, ensure continuity is present between terminals B and FP. Apply battery voltage between terminals B and FC. Ensure continuity is present between terminals B and FP. If continuity is not as specified, replace relay.

EFI MAIN RELAY

1. Using a DVOM, check for continuity between relay terminals No. 1 and 3. (Scheme 60) Ensure continuity is not present between terminals No. 2 and 4. If continuity is not as specified, replace relay.
2. Apply battery voltage between relay terminals No. 1 and 3. Using a DVOM, check for continuity between terminals No. 2 and 4. If continuity is not as specified, replace relay.

Scheme 50

1. Starter relay is located in relay block No. 1 in driver kick panel area. Remove starter relay. Using a DVOM, check for continuity between starter relay terminals No. 1 and 3. (Scheme 50)
2. Ensure no continuity is present between relay terminals No. 2 and 4. If continuity is not as specified, replace relay.
3. Apply battery voltage between relay terminals No. 1 and 3. Using a DVOM, check for continuity between relay terminals No. 2 and 4. If continuity is not present, replace relay.

FUEL PUMP & FUEL PRESSURE REGULATOR

1. Turn ignition on. DO NOT start engine. Using a jumper wire, connect terminals FP and +B of check connector. (Scheme 56)
2. Using fingers, ensure fuel pressure is felt in hose from fuel filter. When fuel system is pressurized, a fuel return noise will also be heard. Turn ignition off.
3. If no fuel pressure was felt, check fusible links, fuses (EFI 15-amp and IGN 7.5-amp), EFI main relay, fuel pump, ECU and wiring connections. CAUTION: SLOWLY loosen cold start injector fuel line to avoid fuel spraying onto skin, eyes and vehicle finish.
4. Connect a fuel pressure gauge to cold start injector fuel line. Using a jumper wire, connect terminals FP and +B of check connector. (Scheme 56) Turn ignition on. Check fuel pressure.
5. See «FUEL PRESSURE SPECIFICATIONS»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If fuel pressure is more than specification, replace fuel pressure regulator. If fuel pressure is less than specification, check fuel hoses, hose connections, fuel pump, fuel filter and fuel pressure regulator. FUEL PRESSURE SPECIFICATIONS Application psi (kg/cm 2 ) Ignition On, Engine Off 38-44 (2.7-3.1) Engine Idling (1) 38-44 (2.7-3.1) Engine Idling (2) 33-37 (2.3-2.6) Ignition Off, Engine Off 21 (1.5) (1) With fuel pressure regulator vacuum hose disconnected. (2) With fuel pressure regulator vacuum hose connected.
6. Start engine. Disconnect and plug vacuum hose from fuel pressure regulator. Check fuel pressure. See «FUEL PRESSURE SPECIFICATIONS»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Unplug and connect vacuum hose to fuel pressure regulator.
7. Check fuel pressure. See «FUEL PRESSURE SPECIFICATIONS»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If fuel pressure is not within specification, check fuel pressure regulator and vacuum hose.
8. Turn engine off. Ensure fuel pressure does not drop less than specified value for 5 minutes after engine is turned off. See the «FUEL PRESSURE SPECIFICATIONS»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If fuel pressure is not as specified, check fuel pump, fuel pressure regulator and fuel injectors. Remove fuel pressure gauge.

Scheme 51

1. Start and warm engine to operating temperature. Ensure A/C is off. Connect a tachometer to engine. Disconnect Throttle Position Sensor (TPS) connector. Using a jumper wire, connect terminals IDL and E2 of harness connector. (Scheme 51)
2. Gradually raise engine speed. Observe tachometer as engine RPM is raised. RPM will fluctuate between fuel cut and fuel return points. See «FUEL CUT RPM SPECIFICATIONS»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. FUEL CUT RPM SPECIFICATIONS Application RPM Fuel Cut 1800 Fuel Return 1200
3. If fuel cut system does not function properly, ensure a clearance of.028" (.71 mm) is present between screw and lever on TPS. Ensure wiring harness is okay between TPS connector and ECU connector.

FUEL INJECTORS

1. Start engine. Using a stethoscope, ensure each injector is making a "clicking" noise during operation. If "clicking" noise is not heard, ensure wiring connector is securely fastened.
2. Ensure an injector signal is present on injector harness connector. Turn engine off. Disconnect injector electrical connector. Using a DVOM, measure resistance across injector terminals.
3. Resistance should be approximately 13.8 ohms. If resistance is not as specified, replace fuel injector. Disconnect negative battery cable. Remove injector from engine.
4. Place injector into a container to catch fuel spray. Turn ignition on. DO NOT start engine. Using a jumper wire, connect terminals FP and +B of check connector. (Scheme 56)
5. Connect battery voltage to injector terminals for 15 seconds. Ensure an even cone shaped fuel spray is observed from injector. If fuel spray is not satisfactory, replace injector. If fuel spray is satisfactory, check volume of fuel delivered by fuel injector.
6. Fuel volume should be 2.7-3.4 cu. in. (45-55 cc) for 15 seconds of operation. Check each injector 2-3 times for volume. Maximum volume difference between injectors is.3 cu. in. (5 cc). If volume is not satisfactory, replace injector.
7. Remove battery voltage from injector. With injector still placed in container, observe injector tip. If injector drips more than one drop of fuel within one minute, replace fuel injector.

FUEL PRESSURE CONTROL SYSTEM

1. Ensure water temperature sensor is functioning properly before diagnosing fuel pressure control system. See CODE 22 test in the «TESTS W/CODES»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-tests-wcodes) article. Ensure airflow meter is functioning properly before diagnosing fuel pressure control system. See airflow meter in «ENGINE SENSORS & SWITCHES»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) in this article.
2. Disconnect electrical connector from fuel pressure Vacuum Switching Valve (VSV). Using a DVOM, measure resistance between VSV terminals. Resistance should be 33-39 ohms (cold). If resistance is not within specification, replace VSV.
3. Using a DVOM, check for continuity between each VSV terminal and ground (outside of VSV). If continuity is present, replace VSV. With electrical connector disconnected, ensure air flows between VSV ports.
4. Apply battery voltage between VSV terminals. Apply air to port E. (Scheme 52) Air should flow from port E to filter. If air does not flow as outlined, replace VSV.

Scheme 52

Scheme 53

1. Start engine. Idle engine for approximately 2 minutes. Turn engine off. Ensure a "clicking" sound is heard from ISC immediately after stopping engine.
2. Disconnect ISC valve connector. Using a DVOM, check resistance between terminals specified in «ISC VALVE RESISTANCE»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. (Scheme 53) If resistance is not as specified, replace ISC valve. ISC VALVE RESISTANCE Terminals Ohms B1 & S1 Or S3 10-30 B2 & S2 Or S4 10-30 NOTE: Wait approximately 20 seconds or longer before disconnecting negative battery cable after ignition is turned off.
3. Disconnect negative battery cable. Drain engine coolant. Disconnect ISC valve connector. Disconnect air hose and 2 water by-pass hoses from ISC valve.
4. Apply battery voltage between ISC valve terminals B1 and B2. Repeatedly ground ISC valve terminals S1, S2, S3, S4, S1 in sequence. (Scheme 53) Check that ISC valve moves toward closed position.
5. With battery voltage applied to the ISC valve, repeatedly ground ISC valve terminals S4, S3, S2, S1, S4 in sequence. (Scheme 53) Check that ISC valve moves toward open position. If operation is not as outlined, replace ISC valve.

Scheme 54

1. Remove filters from EGR vacuum modulator. (Scheme 54) Using compressed air, clean filters. Install filters with coarse side facing outside.
2. Using a vacuum tee, connect a vacuum gauge between EGR vacuum hose and EGR valve. To ensure EGR valve is seating, start engine and check idle quality. If EGR valve is not seating, replace EGR valve.
3. With coolant temperature less than 104°F (40°C), vacuum gauge should indicate zero vacuum at 2500 RPM. Warm engine to operating temperature. Raise engine speed to 2500 RPM. Vacuum gauge should indicate low vacuum.
4. Disconnect vacuum hose from port "R" of EGR vacuum modulator. (Scheme 54) Connect port "R" directly to intake manifold using another vacuum hose. Vacuum gauge should indicate high vacuum with engine at 3500 RPM.
5. Engine may misfire slightly. Let engine idle. Remove vacuum gauge and reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. Engine should run rough or stall.
6. Turn engine off. Identify and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger. (Scheme 54) Blow air into port "Q". Air should flow freely out of filter.
7. Start engine and run engine at 3500 RPM. Block ports "P" and "R" with finger. Blow air into port "Q". Air should not flow out of filter. If air flows out of filter, replace EGR vacuum modulator.
8. Turn engine off. Drain coolant from radiator. Remove Bimetallic Vacuum Switching Valve (BVSV). (Scheme 54) With BVSV less than 104°F (40°C), blow air into top port. Air should not pass through BVSV.
9. Heat BVSV to 129°F (54°C). Blow air into top port. Air should pass through BVSV. If BVSV does not operate as outlined, replace BVSV.

DASHPOT

1. Start and warm engine to operating temperature. Ensure idle speed is 700 RPM. Remove cap, filter and separator from dashpot. Raise and hold engine speed to 2500 RPM.
2. Plug small hole in back of dashpot with finger. Release throttle. When throttle is released, engine speed should be 2000 RPM with cooling fan off. After a few seconds, engine should return to idle.
3. If dashpot does not function properly, try adjusting using a Hexagon wrench. If dashpot still will not function properly, replace dashpot. When installing separator, filter and cap, install filter with coarse side facing outside.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Scheme 55

Scheme 56

1. Turn ignition off. Disconnect cold start injector electrical connector. (Scheme 55) Using a DVOM, measure resistance between cold start injector terminals. Resistance should be 2-4 ohms. If resistance is not as specified, replace cold start injector.
2. Disconnect negative battery cable. Remove cold start injector from engine. Place cold start injector into a container to catch fuel spray. Turn ignition on. DO NOT start engine.
3. Using a jumper wire, connect terminals FP and +B of check connector. (Scheme 56) Connect battery voltage to cold start injector terminals. CAUTION: Apply battery voltage to cold start injector and observe fuel spray as quickly as possible.
4. Ensure an even cone shaped fuel spray is observed from cold start injector. If fuel spray is not satisfactory, replace cold start injector. If fuel spray is satisfactory, remove battery voltage from cold start injector.
5. With cold start injector still placed in container, observe cold start injector tip. If injector drips more than one drop of fuel within one minute, replace cold start injector.
6. Using a DVOM, measure resistance of cold start injector time switch. See the «COLD START INJECTOR TIME SWITCH RESISTANCE»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. (Scheme 57) If resistance is not as specified, replace cold start injector time switch.

COLD START INJECTOR TIME SWITCH RESISTANCE

Scheme 57

Scheme 58

Scheme 59

Scheme 60

Scheme 61

Scheme 62

Scheme 63

1. With coolant temperature less than 185°F (85°C), turn ignition on. Cooling fans should not rotate. If cooling fans rotate, check cooling fan relays and water temperature sensor. Check for damaged connectors or an open circuit between cooling fan relay and water temperature sensor.
2. Disconnect water temperature sensor connector. (Scheme 58) With ignition on, cooling fans should operate. If cooling fans do not operate, check cooling fan relays and water temperature sensor. Check for damaged connectors or an open circuit between cooling fan relay and water temperature sensor.
3. Start engine. Warm engine to operating temperature. Cooling fans should operate at low speed. If cooling fans do not operate at low speed, replace water temperature sensor.
4. Warm engine to more than 194°F (90°C). Cooling fans should operate at high speed. If cooling fans do not operate at high speed, replace water temperature sensor.
5. Turn ignition off. Disconnect the cooling fan ECU. (Scheme 58) Using a DVOM, measure resistance and voltage as indicated in the «COOLING FAN ECU SPECIFICATIONS»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Make all measurements from harness side of connector. (Scheme 59) Repair harness as necessary. COOLING FAN ECU SPECIFICATIONS Terminals Condition Value 2 & Ground N/A Continuity 3 & Ground Ignition On Battery Voltage 4 & Ground Ignition On Battery Voltage 5 & 7 (1) 176°F (80°C) Approx. 1530 Ohms 5 & 7 (1) 194°F (90°C) Approx. 1180 Ohms 5 & 7 (1) 203°F (95°C) Approx. 1030 Ohms 6 & Ground N/A Continuity (1) Coolant temperature.
6. Using a DVOM, measure resistance between water temperature sensor terminals. For water temperature sensor location (Scheme 58) See «WATER TEMPERATURE SENSOR RESISTANCE»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If water temperature sensor is not within specification, replace sensor. WATER TEMPERATURE SENSOR RESISTANCE Temperature Ohms 176°F (80°C) 1530 194°F (90°C) 1180 203°F (95°C) 1030
7. Disconnect engine main relay. (Scheme 58) Using a DVOM, check for continuity between relay terminals No. 1 and 3. (Scheme 60) Check for continuity between relay terminals No. 2 and 4. Ensure continuity is not present between relay terminals No. 4 and 5. If DVOM readings are not as specified, replace relay.
8. Apply battery voltage between relay terminals No. 1 and 3. Using a DVOM, check for continuity between relay terminals No. 4 and 5. Ensure continuity is not present between relay terminals No. 2 and 4. If DVOM readings are not as specified, replace relay.
9. Disconnect cooling fan relay No. 1. (Scheme 61) Using a DVOM, check for continuity between relay terminals No. 1 and 2. (Scheme 61) Check for continuity between relay terminals No. 3 and 4. If continuity is not as specified, replace cooling fan relay No. 1.
10. Apply battery voltage between relay terminals No. 1 and 2. Using a DVOM, ensure continuity is not present between relay terminals No. 3 and 4. If continuity is present, replace relay.
11. Disconnect cooling fan relay No. 2. (Scheme 58) Using a DVOM, check for continuity between relay terminals No. 2 and 6. (Scheme 62) Check for continuity between relay terminals No. 1 and 3. Ensure continuity is not present between relay terminals No. 1 and 4. If continuity reading are not as specified, replace relay.
12. Apply battery voltage between relay terminals No. 2 and 6. Using a DVOM, check for continuity between relay terminals No. 1 and 3. Check for continuity between terminals No. 1 and 4. If continuity is not as specified, replace relay.
13. Remove cooling fan relay No. 3. (Scheme 58) Using a DVOM, check for continuity between relay terminals No. 1 and 3. (Scheme 63) Ensure continuity is not present between terminals No. 2 and 4. If continuity is not as specified, replace relay.
14. Apply battery voltage between relay terminals No. 1 and 3. Using a DVOM, check for continuity between terminals No. 2 and 4. If continuity is not as specified, replace relay.
15. Disconnect cooling fan electrical connector. Connect vehicle battery with an ammeter in series to cooling fan connector. (Scheme 64) Ensure cooling fans operate smoothly. Ammeter reading should not exceed specifications in «COOLING FAN AMPERAGE»(/lexus/es/v20-1989-1991/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.

COOLING FAN AMPERAGE

Scheme 64

THEFT DETERRENT SYSTEM IGNITION SWITCH CIRCUIT TEST

1. Turn ignition off. Check ECU-IG fuse. ECU-IG fuse is located in junction block No. 1 in driver kick panel area. If fuse is okay, repair short in wire harness between ECU-IG fuse and theft deterrent ECU terminal No. 2 of 18-pin connector. (Scheme 65) If fuse is okay, go to next step.
2. Disconnect theft deterrent ECU connectors. Theft deterrent ECU is located under dashboard, above glove box. Turn ignition switch to ACC or ON position. Using a DVOM, check for battery voltage on theft deterrent ECU terminal No. 2 of 18-pin connector. If battery voltage is not present, repair open circuit in wire harness between ECU-IG fuse and terminal No. 2 of 18-pin connector. If battery voltage is present, replace theft deterrent ECU and retest system. Theft deterrent ECU is located under dashboard, above glove box.

THEFT DETERRENT SYSTEM KEY UNLOCK WARNING SWITCH CIRCUIT

1. Turn ignition off. Disconnect theft deterrent ECU connectors. Ensure ignition key is in ignition switch.
2. Using a DVOM, check for continuity between theft deterrent ECU terminal No. 6 of 18-pin connector and ground. (Scheme 65) If continuity is not present, check for short or open circuit in key unlock warning switch circuit. If continuity is present, replace theft deterrent ECU and retest system.

THEFT DETERRENT SYSTEM STARTER CUT SYSTEM CIRCUIT

1. If starter does not operate even after theft system has been deactivated, use key to turn front door lock to unlock position. Check starter for operation. If starter still does not operate, go to next step. Theft deterrent ECU is located under dashboard, above glove box.
2. Disconnect theft deterrent ECU connectors. Turn ignition switch to START position. Ensure shift lever is in N or P, or clutch pedal is depressed. Using a DVOM, check for battery voltage between theft deterrent ECU connector terminal No. 1 of 18-pin connector and ground. (Scheme 65)
3. If battery voltage is not present, repair short or open in starter relay circuit. If battery voltage is present, replace theft deterrent ECU and retest system.

Scheme 65

TRANSMISSION

Note. For transmission diagnostic information, refer to the TESTS W/CODES article.

See also:
• BASIC TESTING
• TESTS W/CODES
• AIRFLOW METER RESISTANCE