Engine Controls - System/component Tests: Other Subaru SVX I

High Boost Pressure

If turbocharger controls fail, excessive boost pressures can cause engine knock and overheating. Check wastegate operation, electrical circuits between wastegate duty solenoid and ECU, and ECU.

Low Boost Pressure

Low boost pressure can cause lack of power, poor acceleration, and increased fuel consumption. Check for leaks in intake and exhaust system, incorrect ignition timing, electrical circuits between wastegate solenoid and ECU, and ECU problems.

Oil Leaks

1. Worn turbocharger oil seals can cause excessive oil consumption and White smoke from exhaust. Remove center exhaust pipe, and examine turbocharger from exhaust side. If excessive carbon deposits exist on turbine exhaust side, oil is leaking from turbine.
2. Turbocharger is not necessarily defective when oil is present on blower side. Oil most likely has come from oil vapors contained in blow-by gases present in intake system or defective PCV system.
3. If intake side contains oil and a rattle is present, remove turbocharger. Check end play and side play.

Boost Pressure

1. Unplug wastegate solenoid connector. Ensure engine is at normal operating temperature. Disconnect rubber hose from pressure switch. Using a "T" fitting, connect an air pressure gauge. Use enough hose so gauge may be observed from inside passenger compartment.
2. Measure boost pressure at 4600 RPM with wide open throttle. Normal pressure is 6.2-7.3 psi (0.43-0.51 kg/cm 2 ). Reconnect wastegate solenoid.
3. If boost pressure is too high, inspect rubber hose connecting intake manifold to wastegate valve. Replace hose if defective. If wastegate valve is not operating and remains closed, replace turbocharger. If boost pressure is too low, replace turbocharger.

Wastegate Valve

Disconnect and plug wastegate valve control vacuum hose from actuator. Connect test hose to wastegate valve actuator. Apply 9-10 psi (0.6-0.7 kg/cm 2 ) air pressure to test hose; wastegate valve linkage should operate. Replace wastegate valve if linkage does not operate.

End Play & Side Play

Maximum end play on turbine shaft should be 0.0035" (0.09 mm). Maximum side play should be 0.0067" (0.17 mm). Measure side play while moving intake and exhaust side of shaft simultaneously. Replace turbocharger assembly if measurements are not as specified.

Ground Circuits

1. Turn ignition off. Using DVOM in ohmmeter mode, backprobe each ECU ground terminal. See ECU GROUND TERMINAL IDENTIFICATION table. Resistance should be zero ohms. If resistance is not close to zero ohms, repair open to ground.
2. Start engine. With DVOM in voltmeter mode, backprobe each ground terminal. Voltage should be less than one volt. If voltage is greater than one volt, check for open, corrosion, or loose connection on ground lead.

ECU GROUND TERMINAL IDENTIFICATION

Power Circuits (Ignition Off)

Turn ignition off. Check for battery voltage between ECU power terminals and ground. See ECU POWER TERMINAL IDENTIFICATION table. If battery voltage does not exist, check fuse or fusible link. Fuses are located under instrument panel. On some models, an auxiliary fuse panel is located in engine compartment. Fusible links are in engine compartment. If fuse or fusible link is okay, check for an open in wire between fuse/fusible link and ECU. See WIRING DIAGRAMS article.

Power Circuits (Ignition On)

Turn ignition on. Check for battery voltage between ECU power terminals and ground. See ECU POWER TERMINAL IDENTIFICATION table. If battery voltage does not exist, check fuse. If fuse is okay, check for an open in wire or a defective ignition switch. See WIRING DIAGRAMS article.

Power Circuits (Cranking)

1. Using voltmeter, backprobe appropriate ECU terminal. See ECU POWER TERMINAL IDENTIFICATION table. Hold ignition switch in START position. Battery voltage should exist between ECU terminal and ground only when ignition switch is in START position.
2. If battery voltage does not exist, check fusible link. Fusible links are in engine compartment. If fusible link is okay, check for open wire between fusible link and ECU terminal, or for defective ignition switch. See WIRING DIAGRAMS article.

ECU POWER TERMINAL IDENTIFICATION

A/C SWITCH

See WIRING DIAGRAMS article. Test switch and circuits as necessary.

MASS AIRFLOW SENSOR (IMPREZA)

1. Turn ignition on. Using voltmeter, backprobe ECU connector terminal B5 (White wire). If voltage is greater than 0.3 volt, check White wire between MAF sensor and ECU terminal B5 for short to voltage. If wire is okay, temporarily substitute known good ECU. Retest system.
2. Using voltmeter, backprobe ECU connector terminal C1 (Black/Blue wire). If voltage is greater than zero volts, check Black/Blue wire between Mass Airflow (MAF) sensor and ECU terminal C1 for short to voltage. If wire is okay, temporarily substitute known good ECU. Retest system.
3. Start and idle engine. Using voltmeter, backprobe ECU connector terminal B5 (White wire). If voltage is not 0.8-1.2 volts, repair White wire between MAF sensor and ECU terminal B5.
4. Using voltmeter, backprobe ECU connector terminal C1 (Black/Blue wire). If voltage exists, check Black/Blue wire between MAF sensor and ECU terminal C1 for short to voltage. If wire is okay, temporarily substitute known good ECU. Retest system.
5. Turn ignition off. Unplug connector from MAF sensor. Turn ignition on. Check for battery voltage at MAF sensor connector terminal No. 1 (Yellow/Green wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair Yellow/Green wire from main relay. See WIRING DIAGRAMS article.
6. Turn ignition off. Unplug connectors from ECU. Check Black/Blue, White, and Black/Red wires between MAF sensor and ECU for shorts or opens. Repair as necessary.
7. If all wires are okay, temporarily substitute known good MAF sensor. Retest system. If system still malfunctions, temporarily substitute known good ECU. Retest system.

MASS AIRFLOW (MAF) SENSOR (EXCEPT IMPREZA)

Remove rubber cover from electrical connector on airflow sensor. Backprobe between terminals to make voltage measurements. Unplug connector to make resistance measurements. See MAF SENSOR TEST SPECIFICATIONS table. If readings are not as specified, check wiring. See WIRING DIAGRAMS article. If wiring is okay, replace airflow sensor.

MAF SENSOR TEST SPECIFICATIONS

BAROMETRIC PRESSURE (BARO) SENSOR (JUSTY & LEGACY)

See HIGH ALTITUDE COMPENSATOR under EMISSION SYSTEMS & SUB-SYSTEMS.

CLUTCH SWITCH (JUSTY)

See WIRING DIAGRAMS article. Test switch and circuits as necessary.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Disconnect coolant temperature sensor connector. Measure resistance between sensor terminals at temperatures specified. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE table.

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE

CRANKSHAFT POSITION (CKP) SENSOR

For testing information, see appropriate SELF-DIAGNOSTICS article.

EGR TEMPERATURE SENSOR (LOYALE CALIF.)

See appropriate SELF-DIAGNOSTICS and WIRING DIAGRAMS articles.

ELECTRICAL LOAD SENSORS (JUSTY)

See WIRING DIAGRAMS article. Test switch and circuits as necessary.

OXYGEN (O2) SENSOR

For testing procedures, see appropriate trouble codes for rich or lean running. See appropriate SELF-DIAGNOSTICS article. Also see WIRING DIAGRAMS article.

P/N SWITCH (EXCEPT JUSTY)

See appropriate SELF-DIAGNOSTICS and WIRING DIAGRAMS articles. Test switch and circuits as necessary.

THROTTLE POSITION SENSOR (OR SWITCH)

For testing and adjustments, see ADJUSTMENTS and appropriate SELF-DIAGNOSTICS articles.

PRESSURE SENSOR

For testing, see appropriate SELF-DIAGNOSTICS article. Also see WIRING DIAGRAMS article.

VEHICLE SPEED SENSOR (VSS)

For testing, see appropriate SELF-DIAGNOSTICS article. Also see WIRING DIAGRAMS article.

EGR Solenoid

See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS. See appropriate SELF-DIAGNOSTICS article for appropriate trouble codes.

Fuel Injector(s)

1. Connect tachometer to engine. Start and idle engine. Unplug harness connector from injectors one at a time. Engine idle speed should drop 100-300 RPM as each injector is disconnected. If engine idle speed does not drop, check wiring connector, injector resistance, and injection signal from computer.
2. Turn ignition off. Unplug connector from each injector. Measure injector resistance. See INJECTOR RESISTANCE SPECIFICATIONS table. If resistance is not to specification, replace injector.

INJECTOR RESISTANCE SPECIFICATIONS

Kickdown Relay Control (TBI)

For testing procedures, see appropriate SELF-DIAGNOSTICS article.

Fuel Pump Relay

For testing procedures, see BASIC TESTING article. Also see WIRING DIAGRAMS article.

Main Relay

For testing procedures, see BASIC TESTING article. Also see WIRING DIAGRAMS article.

Purge Control Solenoid Valve

See FUEL EVAPORATIVE SYSTEM (EVAP) under EMISSION SYSTEMS & SUB-SYSTEMS. See appropriate SELF-DIAGNOSTICS article for appropriate trouble codes.

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC TESTING article.

Feedback System

Manufacturer recommends performing complete inspection of self-diagnostic system. This includes checking mechanical condition of engine, available fuel to injectors, and ignition. Repair or replace components as required, and test drive vehicle.

AUXILIARY AIR VALVE (JUSTY)

1. With engine running, pinch hose between Auxiliary Air Valve (AAV) and intake manifold. AAV is located near throttle body. Engine speed should drop about 100 RPM with engine warm, and more with engine cold. Release hose. Check that engine returns to previous speed.
2. If RPM is not as specified, turn ignition off. Check AAV resistance. If resistance is either zero or infinity, replace AAV. Check AAV solenoid for short to ground. If short exists, replace solenoid.
3. Check for battery voltage at harness connector at Blue wire of AAV electrical connector. If battery voltage does not exist, check main relay, fuses, and power source.

BY-PASS AIR CONTROL VALVE (LOYALE)

1. With engine running, unplug electrical connector from by-pass air control valve. By-pass air control valve is located near throttle body. Engine speed should drop slightly with engine warm, and significantly with engine cold. Reconnect wiring. Engine speed should return to previous value.
2. If engine speed does not return to previous value, turn engine off. Turn ignition on. Check for battery voltage at Black/White wire of Air Control Valve (ACV) electrical connector. See WIRING DIAGRAMS article.
3. Turn ignition off. Measure resistance between ACV terminals. If resistance is not 7.3-13.0 ohms, replace ACV. Check ACV solenoid for short to ground. If short exists, replace ACV.
4. Reconnect wiring to ACV. Unplug connector at ECU. Turn ignition on. Check for battery voltage at terminal C45 (Green/Red wire) of ECU connector. If voltage is not as specified, check harness between ACV and ECU.
5. Turn ignition off. Reconnect wiring to ECU. Turn ignition on. Backprobe terminal C45 (Green/Red wire) of ECU. Voltage should be one volt or less for about one minute after ignition is turned on. After one minute, voltage should be at least 10 volts. If voltage is not as specified, check for a bad ground, problem with ECU circuits (sensors) or faulty ECU.

BY-PASS AIR CONTROL VALVE (LEGACY & SVX)

Turn ignition off. Unplug by-pass air control valve harness connector. By-pass air control valve is located near throttle body. Measure resistance between valve terminals No. 1 (White wire on mating connector) and No. 2 (Yellow/Red wire on mating connector). Resistance should be 9 ohms. Measure resistance between terminals No. 2 (Yellow/Red wire on mating connector) and No. 3 (Black wire on mating connector). Resistance should be 9 ohms. If resistance is not as specified, replace by-pass air control valve. See appropriate SELF-DIAGNOSTICS article for more detailed test procedures.

DASHPOT (JUSTY PFI)

To check and adjust dashpot, see ADJUSTMENTS article.

FAST IDLE & IDLE-UP CONTROL DEVICE (JUSTY)

Using a hand vacuum pump, check to see if control device, located at top center of firewall, will hold vacuum. On models equipped with A/C, idle speed should increase when A/C is turned on. On models without A/C, idle speed should increase when headlights, rear defogger, or heater blower is turned on. (Scheme 4)

Scheme 4

IGNITION SYSTEM

Note. For basic ignition checks (coil, wires, crankshaft position sensor), see appropriate SELF-DIAGNOSTICS article.

Electronic Advance

For testing, see ADJUSTMENTS article.

Knock Sensor (Legacy & Loyale)

For testing, see appropriate SELF-DIAGNOSTICS article. Also see WIRING DIAGRAMS article.

Suction Valve

1. Blow air through suction valve air inlet. Valve is located in line between air cleaner and catalytic converter. Air should flow smoothly through valve outlet. If air does not flow through smoothly, reed valve is stuck closed. Replace reed valve.
2. Blow air through valve outlet. If air flows out inlet, reed valve is broken or stuck open. Replace reed valve.
3. Open suction valve. Inspect gasket, inlet case, and outlet case for damage (cracks). Clean reed valve with gasoline and inspect for waves, cracks, or dents in reed valve seat. Inspect for broken or cracked point of reed valve, or rusted stopper. Replace as necessary.

EGR System (Impreza)

See appropriate SELF-DIAGNOSTICS and WIRING DIAGRAMS articles.

EGR System (Loyale & SVX)

1. Apply about 8 in. Hg vacuum to EGR valve with hand vacuum pump. EGR valve is located between intake and exhaust manifolds. With engine warmed up, engine should stall or idle rough.
2. If engine idle does not change, check EGR pipe and gas passages for clogging and leaks. Clean or replace if necessary. When cleaning, inspect exhaust gas inlet to intake manifold for presence of deposits. Inspect EGR inlet pipe for exhaust deposits.

EGR Valve

1. Look through opening in EGR valve body. Warm engine to normal operating temperature. Increase engine speed and check whether valve shaft moves when engine reaches 3500-4000 RPM under no-load condition.
2. If shaft does not move, remove valve and manually check valve movement. If valve appears okay, check vacuum lines for leaks. Clean or replace valve if it does not operate properly. NOTE: When cleaning EGR valve, DO NOT wash in solvent or degreaser, or permanent damage to valve diaphragm will result.
3. Press valve diaphragm and inspect valve seat area. Inspect valve inlet and outlet for deposits. Clean as necessary. Blow clean with compressed air. Recheck valve operation by applying 8 in. Hg vacuum with hand vacuum pump.

FUEL EVAPORATIVE SYSTEM (EVAP)

Charcoal Canister

1. Disconnect vacuum hose from canister purge vent port (main purge vent on turbo). (Scheme 5) Blow air into canister purge vent port. Airflow will be blocked if valve is operating properly.
2. Disconnect hoses from fuel tank and carburetor ports on canister. Blow air into each port. Air should flow into canister.
3. On turbo models, remove secondary purge hose. Blow into hose. Air should flow with a slight resistance.

Scheme 5

2-Way Valve

Remove valve. Valve is located near fuel tank. Mark hoses for reinstallation. Blow air into each valve port. Air should flow through valve with light resistance. Visually inspect valve for cracks.

1. Measure resistance between terminals of solenoid. See PURGE CONTROL SOLENOID VALVE RESISTANCE table. If resistance is not as specified, replace solenoid valve.
2. Check valve winding for short to ground. Apply battery voltage to valve terminals. Verify passage opens and closes as voltage is applied and removed. Replace valve if winding is shorted, or if operation is not as specified. (Scheme 6)

PURGE CONTROL SOLENOID VALVE RESISTANCE

Scheme 6

BARO sensor is located in ECU. If appropriate trouble code appears, replace ECU.

POSITIVE CRANKCASE VENTILATION (PCV)

Information is not available from manufacturer.