Engine Controls - System/component Tests Lexus ES XV10

INTRODUCTION

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

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.

COMPUTERIZED ENGINE CONTROLS

Power Circuits

1. Ensure ignition is off. Disconnect connectors from ECU. Remove connector locks so ECU connector can be easily backprobed. (Scheme 45) Reconnect ECU connectors.
2. Turn ignition on. Using a DVOM, measure voltage between ground and ECU terminals BATT, IG SW, M-REL, +B and +B1. (Scheme 46) Battery voltage should be present.
3. If battery voltage is not present, check MAIN fuse and EFI fuse. Also ensure wiring harness is not open or shorted. If fuses and wiring harness are okay and conditions indicate ECU may be faulty, substitute a known good ECU. If condition improves, replace original ECU.

Scheme 45

Scheme 46

Ground Circuits

1. Ensure ignition is off. Disconnect connectors from ECU. Remove connector locks so ECU connectors can be easily backprobed. (Scheme 45) Reconnect ECU connectors.
2. Using an ohmmeter, check for continuity to ground on ECU terminals ISC1, ISC2, E1, E01 and E02. (Scheme 46) Resistance should be zero ohms. If resistance is not zero ohms, repair open to ground.
3. Using a DVOM, touch negative lead of voltmeter to a good ground. Touch positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, corrosion and/or loose connection on ground lead.

Airflow Meter Air Temperature Sensor Resistance

Turn ignition off. Disconnect airflow meter connector. Using a DVOM, measure resistance between airflow meter terminals. (Scheme 47) For resistance specifications, see AIRFLOW METER AIR TEMPERATURE SENSOR RESISTANCE table.

AIRFLOW METER AIR TEMPERATURE SENSOR RESISTANCE

Scheme 47

Airflow Meter Measuring Plate Resistance

Using a DVOM, measure resistance between airflow meter terminals while moving airflow measuring plate inside airflow meter. For resistance specifications, see AIRFLOW METER MEASURING PLATE RESISTANCE table.

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 an ohmmeter, check for continuity across switch terminals when clutch pedal switch is depressed. Continuity should not exist when clutch pedal 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. Using a DVOM, check for continuity between terminals specified in appropriate NEUTRAL START SWITCH CONTINUITY table. (Scheme 48) If continuity is not as specified, replace neutral start switch.

NEUTRAL START SWITCH CONTINUITY

Scheme 48

THROTTLE POSITION SENSOR (TPS)

Turn ignition off. Disconnect TPS connector. Using a DVOM, measure resistance between specified TPS terminals in appropriate TPS SPECIFICATIONS table. (Scheme 49)

TPS SPECIFICATIONS

Scheme 49

CIRCUIT OPENING RELAY

1. Turn ignition off. Circuit opening relay is located under right side of instrument panel, above glove box. Remove relay from vehicle. Using an ohmmeter, check for continuity between relay terminals STA and E1. (Scheme 50) Check for continuity between terminals IG and FC. Ensure continuity does not exist between terminals "B" and FP. If continuity is not as specified, replace relay.
2. Apply battery voltage between terminals STA and E1. Using an ohmmeter, ensure continuity is present between terminals "B" and FP.

Scheme 50

EFI MAIN RELAY

1. EFI main relay is located in engine compartment. Using an ohmmeter, check for continuity between relay terminals No. 1 and 3. Ensure continuity is not present between terminals No. 2 and 4. If continuity is not as specified, replace relay. (Scheme 51)
2. Apply battery voltage between relay terminals No. 1 and 3. Using an ohmmeter, check for continuity between terminals No. 2 and 4. If continuity is not present, replace relay.

Scheme 51

STARTER RELAY

1. Remove starter relay. Starter relay is located under instrument panel, above glove box. Use an ohmmeter and check for continuity between starter relay terminals No. 1 and 3. (Scheme 52) Ensure no continuity is present between relay 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 an ohmmeter, check for continuity between relay terminals No. 2 and 4.

Scheme 52

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC TESTING article in the ENGINE PERFORMANCE Section.

Fuel Cut System

1. Start and warm engine to operating temperature. Turn A/C off. Connect tachometer test probe to check connector terminal IG. NOTE: DO NOT allow tachometer terminal to touch ground as it could result in damage to ignitor and/or ignition coil. Some tachometers may not be compatible with ignition system.
2. Increase engine speed to 2500 RPM and check for injector operating noise. See «FUEL CUT RPM SPECIFICATIONS»(/lexus/es/xv10-1991-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. When throttle lever is released, injector operating noise should stop momentarily, then resume. See «FUEL CUT RPM SPECIFICATIONS»(/lexus/es/xv10-1991-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Remove tachometer.

FUEL CUT RPM SPECIFICATIONS

Scheme 53

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 53)
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 1.8-2.16 ozs. (54-64 cc) for 15 seconds of operation. Check each injector 2-3 times for volume. Maximum volume difference between injectors is.16 ozs. (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 coolant temperature sensor is functioning properly before diagnosing fuel pressure control system. See CODE 22 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. Ensure airflow meter is functioning properly before diagnosing fuel pressure control system. See «AIRFLOW METER»(/lexus/es/xv10-1991-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) in ENGINE SENSORS & SWITCHES.
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 54) Air should flow from port "E" to filter. If air does not flow as indicated, replace VSV.

Scheme 54

Scheme 55

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. Connect battery voltage to cold start injector terminals. CAUTION: Immediately observe fuel spray after applying battery voltage to cold start injector.
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 «COLD START INJECTOR TIME SWITCH RESISTANCE»(/lexus/es/xv10-1991-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. (Scheme 56) If resistance is not as specified, replace cold start injector time switch.

COLD START INJECTOR TIME SWITCH RESISTANCE

Scheme 56

Scheme 57

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 table. (Scheme 57) 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 and S4 in sequence. (Scheme 57) Ensure ISC valve moves toward closed position.
5. With battery voltage applied to ISC valve, repeatedly ground ISC valve terminals S4, S3, S2 and S1 in sequence. (Scheme 57) Ensure ISC valve moves toward open position. If operation is not as outlined, replace ISC valve.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article in the ENGINE PERFORMANCE Section.

IGNITION COILS

Turn ignition off. Disconnect wires from ignition coil. Using an ohmmeter, check primary coil resistance on ignition coil. (Scheme 58) For resistance specifications, see IGNITION COIL RESISTANCE table.

IGNITION COIL RESISTANCE

Scheme 58

Scheme 59

1. Remove filters from EGR vacuum modulator. (Scheme 59) Using compressed air, clean filters. Install filters with coarse side facing outward.
2. Using a vacuum "T", 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 approximately 2.76 in. Hg.
4. Disconnect vacuum hose from port "R" of EGR vacuum modulator (lower of 2 ports on side of modulator). (Scheme 59) 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. If results are as indicated, system is okay.

EGR Vacuum Modulator Check

1. Turn engine off. Label and disconnect all vacuum hoses from EGR vacuum modulator. Block ports "P" and "R" with finger (twin ports on side of modulator). (Scheme 59) Blow air into port "Q" (single port on side of modulator). Air should flow freely out of filter.
2. Start engine, and run it 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.

Bimetallic Vacuum Switching Valve

1. Turn engine off. Drain coolant from radiator. Remove Bimetallic Vacuum Switching Valve (BVSV). (Scheme 59) With BVSV less than 104°F (40°C), blow air into top port. Air should not pass through BVSV.
2. 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.

EVAP Canister

1. Visually inspect EVAP canister and hoses for cracks and damage. Disconnect hoses from canister, and blow into canister port from fuel tank. Air should flow from other ports. Blow air into canister purge port. Air should not flow from other ports.
2. Clean canister filter by blowing a maximum of 43 psi (3 kg/cm 2 ) of compressed air through fuel tank port while blocking purge port outlet. No charcoal should come out. DO NOT attempt to wash canister.

1. Drain coolant, and remove Bimetallic Vacuum Switching Valve (BVSV). BVSV is located on coolant outlet. Cool BVSV to less than 95°F (35° C). Blow air into upper BVSV vacuum port. Air should not flow through BVSV ports.
2. Heat BVSV in water to greater than 130°F (55°C). Blow air into upper BVSV vacuum port. Air should flow from upper BVSV vacuum port through lower BVSV vacuum port.

PCV Valve

1. Remove PCV valve from cylinder head cover. Attach a clean hose to cylinder head side of PCV valve. Blow into attached hose. Air should pass freely through PCV valve.
2. Reverse PCV valve, and place clean hose over intake manifold side of PCV valve. Blow air into attached hose. Air should not pass easily through PCV valve. If either condition is not met, replace PCV valve.
3. Inspect all PCV hoses, connections and gaskets for leaks and damage. Repair or replace PCV valve as necessary.

Dashpot

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

MISCELLANEOUS CONTROLS

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

Hydraulic Cooling Fan System

1. Cooling fan ECU controls hydraulic pressure acting on hydraulic motor, controlling speed of cooling fan in response to engine and air conditioner.
2. Hydraulic pump is driven by a drive belt. On some models, hydraulic pump may be integral with power steering pump. Solenoid valve adjusts volume of oil sent from hydraulic pump to hydraulic motor which drives fan directly, controlling fan speed. Oil is cooled by an oil cooler before returning to reservoir tank. Solenoid valve is controlled by cooling fan ECU in response to engine RPM, coolant temperature and A/C signals.

Cooling Fan ECU

1. Disconnect negative battery cable. Turn ignition off and wait 20 seconds. Remove cover under instrument panel. Remove lower instrument panel cover and glove box door assembly. Disconnect cooling fan ECU.
2. Reconnect negative battery cable. Using a DVOM, measure resistance and voltage as indicated in COOLING FAN ECU SPECIFICATIONS table. Make all measurements from harness side of connector. Repair harness as necessary.

COOLING FAN ECU SPECIFICATIONS

Coolant Temperature Sensor

Using a DVOM, measure resistance between coolant temperature sensor terminals. For coolant temperature sensor location (Scheme 60) See COOLANT TEMPERATURE SENSOR RESISTANCE table. If coolant temperature sensor is not within specification, replace sensor.

COOLANT TEMPERATURE SENSOR RESISTANCE

Scheme 60

Engine Main Relay

1. Disconnect engine main relay. (Scheme 61) Use an ohmmeter to check for continuity between relay terminals No. 1 and 3. (Scheme 61) Check for continuity between relay terminals No. 2 and 4. Ensure continuity is not present between relay terminals No. 4 and 5. If continuity is not as specified, replace relay.
2. Apply battery voltage between relay terminals No. 1 and 3. Using an ohmmeter, check for continuity between relay terminals No. 4 and 5. Ensure continuity is not present between relay terminals No. 2 and 4. If continuity readings are not as specified, replace relay.

Scheme 61

See also:
• AIRFLOW METER AIR TEMPERATURE SENSOR RESISTANCE