Engine Controls - System/component Tests Toyota 4Runner II

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.

AIRFLOW METER

Turn ignition off. Unplug wiring connector from air- flow meter. Note terminal identification. (Scheme 118)and (Scheme 119). Use ohmmeter to measure resistance between specified terminals. See AIRFLOW METER RESISTANCE SPECIFICATIONS table. Replace airflow meter if not within specification.

Scheme 117

Scheme 118

Scheme 119

AIRFLOW METER RESISTANCE SPECIFICATIONS

COLD START INJECTOR TIME SWITCH

Turn ignition off. Remove connector from switch. (Scheme 120)and (Scheme 121) for Time Switch Location. Measure resistance across switch terminals at specified temperature. (Scheme 122) Replace switch if resistance is not within specification. See COLD START INJECTOR TIME SWITCH RESISTANCE SPECIFICATIONS table.

COLD START INJECTOR TIME SWITCH RESISTANCE SPECIFICATIONS

Scheme 120

Scheme 121

Scheme 122

COOLANT TEMPERATURE SENSOR

1. Ensure ignition is off. Unplug connector from sensor. For sensor location (Scheme 120)and (Scheme 121).
2. Using ohmmeter, check resistance between sensor terminals. Replace sensor if resistance is not within specification at specified temperature. (Scheme 123)

Scheme 123

EGR GAS TEMPERATURE SENSOR

1. Remove sensor from side of EGR valve. Place threaded end of sensor and thermometer in container of oil. (Scheme 124)
2. Attach ohmmeter to sensor terminals. Heat oil and note resistance at specified temperature. See «EGR TEMPERATURE SENSOR SPECIFICATIONS»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Replace sensor if not within specification.

EGR TEMPERATURE SENSOR SPECIFICATIONS

Scheme 124

KNOCK SENSOR

Probable causes of knock sensor problems include the following

1. Open or short in knock sensor circuit.
2. Knock sensor (looseness etc.).
3. Knock control in ECU is faulty.

Knock sensor problems can also set fault codes 52 and 53. For code charts, see TESTS W/CODES article in the ENGINE PERFORMANCE Section.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

See VACUUM SENSOR under ENGINE SENSORS & SWITCHES in this article.

NEUTRAL/START SWITCH

Unplug switch connector at transmission or transaxle. Note terminal identification. (Scheme 125)-11. Using ohmmeter, check for continuity at specified terminals with gearshift in correct range. See NEUTRAL/START SWITCH SPECIFICATIONS table.

NEUTRAL/START SWITCH SPECIFICATIONS

Scheme 125

Scheme 126

Scheme 127

OXYGEN (O2) SENSOR FEEDBACK VOLTAGE TEST

1. Warm engine to normal operating temperature. Connect analog-type voltmeter to engine check connector VF1 (or VF) and E1 terminals. (Scheme 128)and (Scheme 129). Perform procedures listed in (Scheme 130).
2. Vehicle is equipped with a main O2 sensor and an O2 sensor heater.

Note. Codes No. 21, 25, 26 and 27 are O2 sensor circuit codes. Also check for coolant temperature sensor Code No. 22. Faulty coolant temperature sensor could cause faulty O2 sensor readings.

Scheme 128

Scheme 129

Scheme 130

OXYGEN (O2) SENSOR HEATER

1. Unplug O2 sensor connector. Using ohmmeter, measure resistance between sensor terminals. +B and HT. (Scheme 131) Replace sensor if resistance is not 5.1-6.3 ohms.
2. A Code No. 21 is also an indicator of a problem in O2 sensor circuit. Code No. 21 will set if O2 sensor heater circuit opens or shorts to ground on HT wire from sensor to ECU.

Scheme 131

PICK-UP COILS

See PICK-UP AIR GAP and PICK-UP COIL RESISTANCE in BASIC TESTING article in the ENGINE PERFORMANCE Section.

THROTTLE POSITION SENSOR (TPS)

Turn ignition off. Unplug electrical connector at TPS on throttle body. Note terminal identification. (Scheme 132) Insert specified thickness feeler gauge between throttle stop screw and throttle lever. See TPS RESISTANCE SPECIFICATIONS table. Using an ohmmeter, check for resistance or continuity. Replace or adjust TPS if not within specification.

TPS RESISTANCE SPECIFICATIONS

Scheme 132

VEHICLE SPEED SENSOR

1. Remove combination meter from instrument cluster. Connect ohmmeter between terminals "A" and "B". (Scheme 133)
2. Rotate meter shaft and note reading. Ohmmeter should deflect from continuity to no continuity 4 times per revolution as shaft is rotated. If ohmmeter does not deflect as specified, replace speed sensor.

Scheme 133

4WD SWITCH

Switch is located on right side of transfer case. Remove switch from transfer case. With ohmmeter connected between switch terminal and switch body, there should be continuity when the switch pin is pushed inward.

CIRCUIT OPENING RELAY

Relay is located behind right kick panel. To check circuit opening relay (Scheme 134)and (Scheme 135). Replace relay if continuity is not as specified.

Note. During cranking, there should be 12 volts present at FP terminal of circuit opening relay. This is the fuel pump (or fuel pump relay) line. See WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section for wire color.

Scheme 134

Scheme 135

EFI MAIN RELAY

EFI main relay is located in relay bank, right front engine compartment on Pickup, behind left kick panel on 4Runner. To test EFI main relay (Scheme 136) Replace relay if defective.

FUEL PUMP RELAY

See FUEL DELIVERY under FUEL SYSTEM for testing.

Scheme 136

FUEL SYSTEM

Fuel Pressure Release

Disconnect negative battery terminal. Place container under fitting to be loosened. Use a rag to cover fuel line/component. Slowly loosen fitting, allowing pressurized fuel to spill into container. After fuel system has depressurized, disconnect and plug fitting.

FUEL DELIVERY

For fuel pump pressure and fuel pressure regulator testing, see BASIC TESTING article in the ENGINE PERFORMANCE Section.

Fuel Injectors

1. Turn ignition off. Unplug each injector connector. Measure resistance across both terminals. If resistance is not 13.8 ohms measured at 68°F (20°C), replace fuel injector.
2. To check injector spray pattern and volume, relieve fuel system pressure. Remove injectors from engine. Disconnect fuel hose from fuel filter outlet. Use Fuel Pressure Gauge (09268-41045) to "T" fuel injector between fuel filter and fuel pressure regulator. (Scheme 137)and (Scheme 138).
3. Place injector into clean container. Place tube on end of injector to prevent fuel from spilling. Connect Fuel Injector Tester (09842-30070) or trigger box with appropriate resistor to fuel injector. Turn ignition on, with engine off.
4. Connect jumper wire to engine check connector terminals FP and +B to pressurize fuel system. For engine check connector locations (Scheme 128)and (Scheme 129). Connector terminals are marked on inside of check connector cover.
5. Trigger injector for 15 seconds. Measure volume and check spray pattern. Test each injector 2-3 times. Replace injector if volume is not 2.7-3.4 cu. in. (45-55 cc). Maximum difference between each injector is.3 cu in. (5 cc).
6. Disconnect injector trigger. Fuel leakage from end of injector should be one drop or less in one minute. Replace injector if leakage is more than specified.

Scheme 137

Scheme 138

Fuel Pressure-Up System

1. Ensure coolant temperature sensor, air temperature sensor (in airflow meter) and circuits are operating correctly. See «ENGINE SENSORS & SWITCHES»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests). NOTE: The ECU uses signal from coolant temperature sensor to control ground circuit for fuel pressure-up vacuum switching valve.
2. Fuel pressure-up system is controlled by ECU through a vacuum switching valve. The vacuum switching valve is fed current through the EFI main relay when the ignition is turned on. ECU controls the ground circuit. ECU will activate vacuum switching valve for 90-180 seconds when restarting engine at normal operating temperature.
3. Remove vacuum switching valve from vehicle. VSV is located on top of valve cover on 2.4L, on right fenderwell on 3.0L. Check for continuity across valve wiring terminals. Resistance should be about 33-50 ohms at room temperature. There should be no continuity between each terminal and body of valve. To check operation (Scheme 139)and (Scheme 140).

Scheme 139

Scheme 140

Deceleration Fuel-Cut System

1. Connect a tachometer to engine (to monitor needle fluctuations). See ADJUSTMENTS article in the ENGINE PERFORMANCE Section for tachometer attaching points. Start engine and warm to operating temperature. Ensure A/C and other accessories are off.
2. Unplug throttle position sensor connector from throttle position sensor. Short terminals IDL and E2 on wire side of connector. (Scheme 141)
3. Gradually raise engine RPM. Fuel-cut operation can be checked by noting the fluctuation of tachometer needle. Fluctuation indicates fuel-cut system is being turned on and off. (Scheme 142) Check that fuel-cut points and fuel return points are within specifications. See «DECELERATION FUEL-CUT & FUEL RETURN RPM»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.

DECELERATION FUEL-CUT & FUEL RETURN RPM

Scheme 141

Scheme 142

Cold Start Injector

1. Disconnect negative battery cable. Disconnect cold start injector wiring harness connector. Check resistance between terminals of injector. Replace injector if resistance is not 2-4 ohms. If resistance is okay, relieve fuel system pressure.
2. Remove cold start injector from vehicle. Install fuel hose to injector. Install system Union Adapters (9268-41045) to delivery pipe and cold start injector. Connect fuel hose to union adapters. (Scheme 143) Connect Jumper Harness (9842-30050) to cold start injector.
3. Place container under cold start injector. Connect jumper wire to engine check connector terminals FP and B+ to pressurize fuel system. For engine check connector locations (Scheme 128)and (Scheme 129). Turn ignition on, with engine off. CAUTION: Perform cold start injector connector test in shortest possible time.
4. Connect probes of Fuel Injection Tester (09842-30070) to battery. Connect other end of tester to cold start injector. (Scheme 143) Ensure fuel spray is an even cone shape.
5. Disconnect fuel injector tester harness and observe cold start injector. Maximum leakage should be one drop per minute with fuel pressure applied. Clean or replace cold start injector if defective.

Scheme 143

Note. Cold start injector is controlled by cold start injector time switch when ignition switch is turned on.

For test procedures, see ENGINE SENSORS & SWITCHES .

AUXILIARY AIR VALVE SYSTEM (2.4L)

1. With engine coolant less than 176°F (80°C), install tachometer. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section for tachometer attaching points.
2. Start engine. With engine idling, turn idle speed adjusting screw to bottom of bore while counting number of revolutions. Engine speed should drop noticeably.
3. Return idle adjusting screw to original position. Warm engine to normal operating temperature. Repeat step 2). Engine speed should not change or should drop slightly.
4. If engine RPM does not respond as indicated, check for vacuum leaks after the valve or restricted chamber in auxiliary air valve circuit. If no defects are found, replace auxiliary air valve.

IGNITION SYSTEM

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

Probable causes of knock sensor problems include the following

1. Open or short in knock sensor circuit.
2. Knock sensor (looseness etc.).
3. Knock control in ECU is faulty.

On models equipped with knock sensor, diagnosis is in Code 52 and Code 53 charts. For code charts, see TESTS W/CODES article in the ENGINE PERFORMANCE Section.

System Test (2.4L)

1. Check hoses and tubes for cracks, kinks, damage, or loose connections. Check Pulse Air System (PAS) cold operating condition. (Scheme 144)
2. Ensure coolant temperature is less than 86°F (30°C). Start engine and set idle. Disconnect PAS vacuum hose from air cleaner. (Scheme 145) Check for air bubbling noise from PAS vacuum hose.
3. When engine temperature is greater than 104°F (40°C), air bubbling noise from PAS vacuum hose should not be heard. Race engine and quickly close throttle. Air bubbling noise from PAS vacuum hose should be heard and then momentarily stop.

Scheme 144

Scheme 145

System Test (3.0L)

1. Check hoses and tubes for cracks, kinks, damage, or loose connections. Check Pulse Air (PAS) system cold operation. (Scheme 146)
2. Ensure coolant temperature is less than 77°F (25°C). Start engine and allow to idle. Disconnect pulse air hose from air pipe. (Scheme 147) Check for air bubbling noise from air pipe.
3. Check hot system operation. When engine temperature is at normal operating temperature, bubbling noise should not be heard from air pipe. Race engine to 2000 RPM. Ensure bubbling noise stops momentarily.

Pulse Air System (Reed) Valve (3.0L)

Apply vacuum to reed valve diaphragm. Blow air into reed valve pipe and ensure reed valve is open. Release vacuum and ensure reed valve is closed.

Vacuum Switching Valve (VSV)

1. Connect battery voltage to vacuum control valve. (Scheme 148) Blow into port "E" and ensure air comes out of port "G". Disconnect battery voltage and blow into port "E". Air should come out of air filter. If VSV does not function as described, replace VSV.
2. Check for short. Using an ohmmeter, ensure no continuity is present between VSV terminals and VSV body. Check for open. Measure resistance between VSV terminals. Resistance should be 30-50 ohms at 68°F (20°C). If VSV valve resistance is not within specification, replace VSV valve.

Vacuum Check Valve

Ensure air flows from Orange port to Black port. Air should not flow from Black port to Orange port.

Scheme 146

Scheme 147

Scheme 148

Scheme 149

Scheme 150

Scheme 151

1. Ensure modulator filter is clean and in good condition prior to performing test. Clean filter with compressed air. Disconnect vacuum hose from EGR valve.
2. Using a "T" connector, connect a vacuum gauge in EGR valve vacuum line. Ensure engine starts and runs smoothly at idle. This ensures proper seating of EGR valve.
3. Different vacuum switching valves are used depending on model. (Scheme 149)-35. The Bimetallic Vacuum Switching Valve (BVSV), Vacuum Switching Valve (VSV) and EGR modulator can be checked with engine coolant temperature less than minimum temperature and specified engine RPM in accordance with application. See «EGR SPECIFICATIONS»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.
4. Operate engine with engine coolant temperature less than minimum temperature and specified RPM. No vacuum reading should be obtained when operated with engine coolant temperature less than minimum temperature.
5. Operate engine at normal operating temperature and specified RPM. See «EGR SPECIFICATIONS»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. A low vacuum reading should be obtained.
6. Disconnect hose from the "R" port of EGR vacuum modulator. (Scheme 152)
7. Using additional hose, connect "R" port directly to intake manifold. High vacuum reading should be obtained at specified engine RPM. See «EGR SPECIFICATIONS»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. NOTE: Engine should misfire due to large amounts of exhaust gas being injected into intake manifold.
8. To check EGR valve, apply vacuum directly to EGR valve with engine idling. Engine should run rough or stall. If system did not operate as described, each component should be tested.

EGR SPECIFICATIONS

EGR Vacuum Modulator

1. Disconnect all hoses. Block ports "P" and "R". Apply air pressure to port "Q". (Scheme 152) Air should pass through the air filter side of modulator freely.
2. Operate engine at 3500 RPM. Repeat test procedures in step 1). Strong resistance of airflow should be felt. Replace EGR vacuum modulator if resistance is not felt. Reconnect vacuum hoses to proper locations

Scheme 152

Bimetallic Vacuum Switching Valve (BVSV) (2.4L)

1. Drain cooling system and remove BVSV. (Scheme 150) Cool BVSV to 86°F (30°C) using cool water.
2. Apply air to the lower port. Air should pass through air filter located on top of valve assembly. Heat BVSV valve to 111°F (44°C).
3. Apply air to the lower port. Air should pass through from the upper port but not through the air filter. Replace assembly if defective.

Vacuum Switching Valve (VSV) (3.0L)

1. Unplug VSV connector. (Scheme 151) Connect battery to VSV terminals. (Scheme 149) Apply air pressure to port "E". Air should pass through air filter. Disconnect battery terminals.
2. Apply air pressure to port "E". Air should now pass through port "G". Using ohmmeter, check for continuity between terminals and VSV body. Replace unit if incorrect airflow or continuity exists.
3. Using ohmmeter, measure resistance between both terminals of valve assembly. Replace valve if resistance is not

FUEL EVAPORATION

Note. (Scheme 153)and (Scheme 154) to identify evaporative emission control systems and operating parameters.

Fuel Odor Or Gas Leaks

Check for disconnected or cracked fuel vapor line or defective components in system. Check all lines and fittings. Check operation of system.

Fuel Tank Or Expansion Tank Deformed

Check for clogged canister, defective vacuum relief filler cap or restricted hoses.

Rough Engine Operation

Check vacuum hose between vacuum solenoid valve (if equipped) and intake manifold for damage or loose connections. Check for malfunctions in all valves. Ensure all vacuum hoses are tight and in good condition.

Bimetallic Vacuum Switching Valve (BVSV)

1. Drain engine coolant. Remove BVSV. Connect hose to top port. Place valve in water that is less than 95°F (35°C). Blow air into hose. Ensure valve is closed.
2. Heat water to 129°F (54°C). Blow air into hose. Ensure valve is open. If valve is not open, replace valve. Apply liquid sealer to threads of valve before installing. Fill cooling system. If BVSV does not operate as described, replace valve.

Charcoal Canister

1. On all models, check for clogged filter and/or stuck check valve by blowing low pressure compressed air into canister tank port. Ensure air flows freely out of other canister ports.
2. Blow air into canister purge port. Ensure air does not flow out of any other port.

Maintenance

1. Inspect fuel tank, canister, vacuum relief filler cap, lines and hoses for damage, leaks and deterioration every 60,000 miles or every 6 years. Replace gasket in vacuum relief filler cap.
2. To clean charcoal canister filter, remove hoses from canister and apply 43 psi (3 kg/cm 2 ) air pressure to fuel tank port. Hold other top ports closed. Ensure that no carbon comes out of bottom port of canister.

Scheme 153

Scheme 154

Fixed Orifice

Visually inspect hose and connections for cracks, leaks or other damage. Clean deposits from orifice with solvent and blow out with compressed air

PCV Valve

Remove PCV valve. Attach hose to PCV valve. Blow air from cylinder head side of valve. Ensure air passes through easily. Blow air from intake manifold side. Ensure air passes through with some restriction. If PCV valve does not function as described, replace PCV valve.

DASHPOT CONTROL SYSTEM

1. Engine must be at normal operating temperature. Check idle speed and adjust if necessary. Remove cap, filter and separator from dashpot. (Scheme 155)
2. Start engine. Maintain engine speed at 2500 RPM. Plug Vacuum Transmitting Valve (VTV) hole with your finger. (Scheme 155)
3. Release throttle. Dashpot should be extended and dashpot setting RPM should be 2000 RPM. If idle speed is incorrect, adjust dashpot. (Scheme 156)
4. To check VTV operation, run engine at dashpot testing RPM for a few seconds. Plug the VTV hole with your finger. Release throttle. Uncover plugged hole. Engine should return to idle in about one second.
5. Install dashpot separator, filter and cap. Install filter with coarser surface facing outward.

Scheme 155

Scheme 156

See also:
• AIRFLOW METER RESISTANCE SPECIFICATIONS
• FUEL DELIVERY