Engine Controls - System/component Tests Toyota Tercel L40

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.

Note. When testing some systems, tachometer may be required. Tachometer must be connected to proper terminals. For tachometer connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS article in the ENGINE PERFORMANCE Section.

ENGINE SENSORS & SWITCHES

Note. Air temperature sensor may be referred to as intake air temperature sensor.

Air Temperature Sensor

1. Ensure ignition is off. Disconnect electrical connector from air temperature sensor. Air temperature sensor is located in the air intake, near the air filter.
2. Using ohmmeter, measure resistance between air temperature sensor electrical terminals. Replace air temperature sensor if resistance is not within specification in relation to the temperature. (Scheme 76)

Scheme 76

Coolant Temperature Sensor (CTS)

1. Ensure ignition is off. Disconnect electrical connector from CTS. The CTS is located in engine coolant passage near cylinder head or thermostat housing. It may be necessary to verify wire colors for proper identification. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. NOTE: The CTS may be also identified by appropriate illustration in THEORY/OPERATION article in the ENGINE PERFORMANCE Section.
2. Using ohmmeter, check resistance between CTS electrical terminals. Resistance should be within specification at designated temperature. (Scheme 77) On all models, replace CTS if resistance is not within specification.

Scheme 77

EGR Gas Temperature Sensor (Calif. Only)

1. Remove EGR gas temperature sensor from side of EGR valve. Place threaded end of sensor and thermometer in container of oil. (Scheme 78)
2. Attach ohmmeter to electrical terminals. Heat oil and note resistance at specified temperature. See EGR GAS TEMPERATURE SENSOR SPECIFICATIONS table. Replace EGR gas temperature sensor if resistance is not within specification.

EGR GAS TEMPERATURE SENSOR SPECIFICATIONS

Scheme 78

Manifold Absolute Pressure (MAP) Sensor

See VACUUM SENSOR under ENGINE SENSORS & SWITCHES.

Neutral/Start Switch

Note. Information for Tercel neutral/start switch is not available from manufacturer.

Oxygen Sensor Feedback Voltage Test

1. Warm engine to normal operating temperature. Connect analog voltmeter to engine check connector VF1 or VF2 and E1 terminals. (Scheme 79) Perform procedures listed in (Scheme 80) and (Scheme 81).
2. Depending on model application, some vehicles may be equipped with a main oxygen sensor, sub-oxygen sensor and a sensor heater. See OXYGEN SENSOR APPLICATION table.

Note. Codes 21, 25, 26, 27 and 28 are oxygen sensor circuit codes. For code charts, see TESTS W/CODES article in the ENGINE PERFORMANCE Section.

OXYGEN SENSOR APPLICATION

Scheme 79

Scheme 80

Scheme 81

Note. For oxygen sensor heater or sub-oxygen sensor heater application, see OXYGEN SENSOR APPLICATION table.

Note. A Code 21 is also an indicator of a problem in oxygen sensor circuit. Code 21 will set if sensor heater circuit opens or shorts to ground on HT wire from sensor to Electronic Control Unit (ECU).

Pick-Up Coils

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

Throttle Position Sensor (TPS)

1. Turn ignition off. Disconnect electrical connector from TPS on throttle body. Note terminal identification. (Scheme 82)
2. Insert specified thickness feeler gauge between throttle stop screw and throttle lever, and check resistance or continuity. See appropriate TPS RESISTANCE SPECIFICATIONS table. Replace or adjust TPS if not within specification.

Note. Some models require that vacuum be applied to throttle opener before checking TPS. See appropriate TPS RESISTANCE SPECIFICATIONS table.

Scheme 82

TPS RESISTANCE SPECIFICATIONS

Note. Vacuum sensor may also be referred to as Manifold Absolute Pressure (MAP) sensor.

Vacuum Sensor

1. Ensure ignition is off. To check vacuum sensor supply voltage, disconnect electrical connector from vacuum sensor.
2. Vacuum sensor is located on center of firewall. NOTE: Vacuum sensor has a vacuum hose connected to it and may be identified by wire colors. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.
3. Turn ignition on. Using voltmeter, measure voltage between terminals VCC and E2 of harness connector. (Scheme 83) Voltage should be within specification. See VACUUM SENSOR SUPPLY VOLTAGE SPECIFICATIONS table. VACUUM SENSOR SUPPLY VOLTAGE SPECIFICATIONS Application Voltage Tercel 4.00-6.00
4. If supply voltage is not within specification, check wiring circuit. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. If supply voltage is correct, turn ignition off and reinstall electrical connector on vacuum sensor.
5. To check vacuum sensor output voltage, turn ignition on. Disconnect vacuum sensor vacuum hose from intake manifold. Connect voltmeter to terminals PIM and E2 of Electronic Control Unit (ECU). (Scheme 84) See ECU LOCATION table. ECU LOCATION Application Location Tercel Bottom Center Of Dash, In Front Of Console
6. Measure and record output voltage under ambient atmospheric pressure. Attach vacuum pump to vacuum sensor.
7. Apply vacuum in specified increments and measure output voltage drop at each increment. See VACUUM SENSOR OUTPUT VOLTAGE DROP SPECIFICATIONS table. Replace vacuum sensor if output voltage drop is not within specification.

VACUUM SENSOR OUTPUT VOLTAGE DROP SPECIFICATIONS

Scheme 83

Scheme 84

Vehicle Speed Sensor

1. Vehicle speed sensor is located on rear of combination meter in instrument cluster. Connect ohmmeter between terminals "A" and "B". Terminals are located near vehicle speed sensor. (Scheme 85)
2. Rotate speedometer cable shaft and note reading. Ohmmeter should deflect from continuity to no continuity 4 times per speedometer cable shaft revolution. Replace vehicle speed sensor if reading does not deflect as specified.

Scheme 85

CIRCUIT OPENING RELAY

1. Ensure ignition is off. Remove circuit opening relay. See CIRCUIT OPENING RELAY LOCATION table. Using ohmmeter, check continuity between specified terminals. (Scheme 86)- (Scheme 88).
2. Check circuit opening relay operation by applying battery voltage and checking continuity between specified terminals. (Scheme 86)- (Scheme 88). Replace circuit opening relay if defective.

Note. Circuit opening relay may also be identified by appropriate illustration in THEORY/OPERATION article in the ENGINE PERFORMANCE Section or wire color. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

CIRCUIT OPENING RELAY LOCATION

Scheme 86

Scheme 87

Scheme 88

EFI MAIN RELAY

1. Ensure ignition is off. Remove EFI main relay. See EFI MAIN RELAY LOCATION table. Using ohmmeter, check continuity between specified terminals. (Scheme 89)
2. Check EFI main relay operation by applying battery voltage and checking continuity between specified terminals. (Scheme 89) Replace EFI main relay if defective.

Note. The EFI main relay may also be identified by appropriate illustration in THEORY/OPERATION article in the ENGINE PERFORMANCE Section or wire color. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

EFI MAIN RELAY LOCATION

Scheme 89

FUEL CONTROL

Note. Fuel injector solenoid resistor may also be referred to as solenoid resistor.

Fuel Injectors

1. Ensure ignition is off. Disconnect electrical connector at fuel injector. Using ohmmeter, measure resistance between fuel injector electrical terminals. Replace fuel injector if resistance is not within specification. See FUEL INJECTOR RESISTANCE SPECIFICATIONS table.
2. To check fuel injector spray pattern and volume, remove fuel injectors. See N - REMOVE/INSTALL/OHAUL article in the ENGINE PERFORMANCE Section. Disconnect fuel hose from fuel filter outlet. Use Delivery Hose (09268-41045) to install fuel injector between fuel filter and fuel pressure regulator. (Scheme 90)
3. Place fuel injector into a clean graduated container. Place vinyl tube on end of fuel injector to prevent fuel spillage. Connect jumper wire between terminals FP and +B of engine check connector. Turn ignition on, with engine off to pressurize fuel system. NOTE: For proper location of engine check connector and terminal identification, see TESTS W/CODES article in the ENGINE PERFORMANCE Section. Jumper wire is installed in engine check connector when checking fuel operation and fuel pressure.
4. Connect fuel injector tester to fuel injector for 15 seconds. Use Fuel Injector Tester (09842-30070).
5. Measure fuel injector volume and check spray pattern. Test each fuel injector 2-3 times. Replace fuel injector if volume is not as specified. See FUEL INJECTOR VOLUME SPECIFICATIONS table. NOTE: Ensure the difference between fuel injector volume on all fuel injectors is within specification. See FUEL INJECTOR VOLUME SPECIFICATIONS table.
6. Disconnect fuel injector tester. Ensure fuel leakage from end of fuel injector is one drop or less in one minute. Replace fuel injector if leakage exceeds specified amount. Turn ignition off and remove test equipment.

FUEL INJECTOR RESISTANCE SPECIFICATIONS

FUEL INJECTOR VOLUME SPECIFICATIONS

Scheme 90

Note. Fuel pressure control system may also be referred to as fuel-pressure up system.

Fuel Pressure Control System

1. Ensure coolant temperature sensor operates correctly. See ENGINE SENSORS & SWITCHES. NOTE: ECU uses signal from coolant temperature sensor to control ground circuit for fuel pressure control VSV.
2. VSV is supplied voltage through EFI main relay. The ECU will activate VSV for approximately 90 seconds when restarting engine at normal operating temperature. Locate and remove fuel pressure control VSV. See FUEL PRESSURE CONTROL VSV LOCATION table. NOTE: Fuel pressure control VSV may also be identified by appropriate illustration in THEORY/OPERATION article in the ENGINE PERFORMANCE Section or wire color. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. FUEL PRESSURE CONTROL VSV LOCATION Application Location Tercel Near Front Of Valve Cover, On Passenger's Side
3. Use ohmmeter to check continuity between VSV electrical terminals. Ensure resistance is within specification. See FUEL PRESSURE CONTROL VSV RESISTANCE SPECIFICATIONS table.
4. Check that no continuity exists between each electrical terminal and VSV body. Replace VSV if resistance is not within specification or continuity exists between electrical connector and VSV body.
5. Test VSV by applying air pressure to designated area and checking air passage, and then applying battery voltage and retesting. (Scheme 91) Replace VSV if defective.

FUEL PRESSURE CONTROL VSV RESISTANCE SPECS

Scheme 91

Scheme 92

Fuel Cut System

1. Install tachometer. Tachometer must be connected to proper terminals. See IDLE SPEED & MIXTURE in ADJUSTMENTS article in the ENGINE PERFORMANCE Section. CAUTION: Some tachometers may not be compatible with ignition system. Consult tachometer manufacturer before connecting tachometer to system. To avoid possible damage to ignitor and/or coil, DO NOT allow tachometer terminal to become grounded.
2. Start engine and warm to normal operating temperature. Ensure all accessories are off. Gradually increase engine RPM to at least 2500 RPM.
3. Using stethoscope, check for fuel injector operating sound. Ensure when throttle lever is released, fuel injector stops operating momentarily (fuel cut RPM) and then resumes operating (fuel return RPM).
4. Ensure fuel return RPM is within specification. See FUEL CUT SYSTEM SPECIFICATIONS table. Shut engine off and disconnect tachometer.

FUEL CUT SYSTEM SPECIFICATIONS

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

Cold Start Injector Time Switch

For test procedures, see ENGINE SENSORS & SWITCHES.

Scheme 93

AUXILIARY AIR VALVE SYSTEM

Note. Tachometer must be installed when checking auxiliary air valve system. Tachometer must be connected to proper terminals. See IDLE SPEED & MIXTURE in ADJUSTMENTS article in the ENGINE PERFORMANCE Section for tachometer connections.

1. Install tachometer. With engine coolant less than 176°F (80°C), remove air intake hose from throttle body.
2. Start engine. Place finger over air valve port to block airflow. (Scheme 94) Engine speed should decrease noticeably.
3. Allow engine to warm to normal operating temperature. Place finger over air valve port to block airflow. Engine speed should not decrease more than 100 RPM for Tercel, or 50 RPM for all others.
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.

Scheme 94

IDLE-UP SYSTEM

Note. Ensure coolant temperature sensor is operating properly before checking idle-up system. For sensor testing, see ENGINE SENSORS & SWITCHES.

1. Remove idle-up system Vacuum Switching Valve (VSV), located near end of valve cover (Tercel) on passenger's side. NOTE: The VSV may also be identified by appropriate illustration in THEORY/OPERATION article in the ENGINE PERFORMANCE Section or wire color. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.
2. Using ohmmeter, measure resistance between VSV electrical terminals. Replace VSV if resistance is not 37-44 for Tercel. Check that no continuity exists between each electrical terminal and VSV body.
3. Test VSV by applying air pressure to designated area and checking air passage, and then applying battery voltage and retesting. (Scheme 95) Replace VSV if defective.

Scheme 95

IGNITION SYSTEM

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

Knock Sensor

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

System Test

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 97)and (Scheme 98). 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 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 table. On all other models, a low vacuum reading should be obtained.
6. On all models, disconnect hose from port "R" of EGR vacuum modulator. (Scheme 96)
7. Using additional hose, connect port "R" directly to intake manifold. High vacuum reading should be obtained at specified engine RPM. See EGR SPECIFICATIONS 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. EGR vacuum modulator is a 3-port type.
2. Disconnect all hoses. Block ports "P" and "R". Apply air pressure to port "Q". (Scheme 96) Air should pass through the air filter side of modulator freely.
3. Operate engine at specified RPM. See EGR VACUUM MODULATOR SPECIFICATIONS table. Repeat test procedures in steps 1) and 2). Strong resistance of airflow should be felt. Replace EGR vacuum modulator if resistance is not felt. Reconnect vacuum hoses to proper locations.

EGR VACUUM MODULATOR SPECIFICATIONS

Scheme 96

VACUUM SWITCHING VALVE (VSV) SPECIFICATIONS

Vacuum Switching Valve (VSV)

1. Unplug VSV connector. (Scheme 98) Connect battery to VSV terminals. (Scheme 97) Apply air pressure to port "E". Air should pass through port "F".
2. Disconnect battery terminals. Apply air pressure to port "E". Air should not pass through port "F". 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 within specification. See VACUUM SWITCHING VALVE (VSV) SPECIFICATIONS table.

Scheme 97

Scheme 98

EGR System Components & Operating Parameters ID (California). Scheme 99

FUEL EVAPORATION

Note. (Scheme 100)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. 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 no carbon comes out of bottom port of canister.

Scheme 100

Evaporative Emission Control System & Operating Parameters ID. Scheme 101

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 102)
2. Start engine. Maintain engine speed at specified testing RPM. See DASHPOT TESTING RPM table. Plug Vacuum Transmitting Valve (VTV) hole with your finger. (Scheme 102)
3. Release throttle. Dashpot should be extended and dashpot setting RPM should be as specified. See DASHPOT TESTING RPM table. If idle speed is incorrect, adjust dashpot. (Scheme 103)
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. Install dashpot separator, filter and cap. Install filter with coarser surface facing outward.

DASHPOT TESTING RPM

Scheme 102

Scheme 103

Throttle Valve Opener

1. Engine must be at normal operating temperature. Ensure idle speed is correct. Disconnect vacuum hose from throttle valve opener and plug hose. (Scheme 104) Raise engine speed to 2500 RPM.
2. Release throttle valve. Check throttle valve opener RPM. See THROTTLE VALVE OPENER RPM table. If throttle valve opener RPM is not as specified, replace throttle body.

THROTTLE VALVE OPENER RPM

Scheme 104