Engine Controls - System/component Tests Mitsubishi Mirage IV

INTRODUCTION

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

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

CONTROL UNIT

Note. For Engine Control Module (ECM) location, see ENGINE CONTROL MODULE (ECM) LOCATION table. To identify ECM power and ground circuits, see WIRING DIAGRAMS article in this section.

Ground Circuits

1. Turn ignition off. Using an ohmmeter, check continuity between chassis ground and ECM ground terminals. See «GROUND TERMINAL ID»(/mitsubishi/mirage/iv-1991-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Ohmmeter should indicate zero ohms. If reading is not zero ohms, check and repair open circuit between ECM connector and ground.
2. Connect voltmeter negative lead to chassis ground. Connect positive lead to ECM ground terminals. See «GROUND TERMINAL ID»(/mitsubishi/mirage/iv-1991-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. (Scheme 34) With engine running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, corrosion or loose connection in ground circuit.

Power Circuits

Turn ignition on. Check for battery voltage on ECM power terminals. See POWER TERMINAL ID table. If battery voltage is not present, check operation of MPI control relay. See RELAYS under MOTORS, RELAYS & SOLENOIDS.

Scheme 34

GROUND TERMINAL ID

POWER TERMINAL ID

ENGINE CONTROL MODULE (ECM) LOCATION

BAROMETRIC PRESSURE SENSOR

Sensor is a part of airflow sensor assembly. See TESTS W/CODES article in this section.

CAMSHAFT POSITION SENSOR

See TESTS W/CODES article in this section.

CLOSED THROTTLE POSITION SWITCH

See THROTTLE POSITION SENSOR in TESTS W/CODES article in this section.

COOLANT TEMPERATURE SENSOR

See TESTS W/CODES article in this section.

CRANKSHAFT POSITION SENSOR

See TESTS W/CODES article in this section.

EGR TEMPERATURE SENSOR (CALIFORNIA)

See TESTS W/CODES article in this section.

IDLE POSITION SWITCH

See THROTTLE POSITION SENSOR in TESTS W/CODES article in this section.

INHIBITOR SWITCH (A/T MODELS)

1. Switch is mounted to automatic transaxle, near shift lever mechanism. Ensure switch is adjusted properly. Switch output can be affected by improper adjustment. Using DVOM, measure resistance between selected terminals to ensure continuity between ignition switch and ECM when shift selector lever is in Park or Neutral position. See «INHIBITOR SWITCH CONTINUITY CHECK»(/mitsubishi/mirage/iv-1991-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.
2. Using DVOM, measure power supply voltage of switch. Disconnect ECM connector. Disconnect inhibitor switch connector. Turn ignition switch to START position. Measure voltage between inhibitor switch and vehicle ground. On all models, inhibitor switch wire color is Black/Yellow. Supply voltage should be battery voltage. If voltage is within specification, go to step 3. If voltage is less than battery voltage, check and repair power supply circuit.
3. Using DVOM, measure inhibitor switch terminal input voltage. Connect ECM connector. Ensure inhibitor switch connector is disconnected. Turn ignition switch to ON position. Measure voltage between inhibitor switch and vehicle ground. Input voltage should be battery voltage. If voltage is within specification, go to step 4. If voltage is less than battery voltage, check and repair circuit.
4. Using DVOM, measure input voltage of ECM. Disconnect ECM connector. Connect inhibitor switch connector. Ensure shift selector lever is in "P" position. Turn ignition switch to ON position. Measure voltage between ECM connector and vehicle ground. See «ECM TERMINAL ID»(/mitsubishi/mirage/iv-1991-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. ECM input voltage should be 8 volts or greater. If voltage is within specification, system is okay. If voltage is less than 8 volts, replace ECM. INHIBITOR SWITCH CONTINUITY CHECK Application (1) Wire Color (2) Wire Color All Models Black/Yellow Black/Red (1) Ignition switch to inhibitor switch circuit. (2) Inhibitor switch to ECM circuit. ECM TERMINAL ID Application (1) Terminal Number All Models 71 (1) (Scheme 34)

INTAKE AIR TEMPERATURE SENSOR

See TESTS W/CODES article in this section.

OXYGEN (O2) SENSOR

See TESTS W/CODES article in this section.

POWER STEERING OIL PRESSURE SWITCH

1. Disconnect switch connector at pump. Using DVOM, check continuity between switch and vehicle ground. Continuity should not exist with wheels straight ahead and engine idling. Continuity should be present when wheels are turned.
2. Check continuity of circuit between switch and ECM. Disconnect power steering oil pressure switch connector and ECM connector. Connect jumper wire between ECM terminal and vehicle ground. See «POWER STEERING PRESSURE SWITCH ECM TERMINAL NUMBER»(/mitsubishi/mirage/iv-1991-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Using DVOM, check for continuity between switch harness connector and vehicle ground. Check and repair circuit if no continuity exists. Go to step 3 if continuity exists.
3. Connect ECM connector. Turn ignition on. Using DVOM, measure voltage at switch harness connector. System is okay if battery voltage exists. Replace ECM if voltage does not exist. POWER STEERING PRESSURE SWITCH ECM TERMINAL NUMBER Application (1) Terminal Number All Models 37 (1) (Scheme 34)

THROTTLE POSITION SENSOR

See TESTS W/CODES article in this section.

VEHICLE SPEED SENSOR

See TESTS W/CODES article in this section.

IAC Motor

See IDLE CONTROL SYSTEM .

RELAYS

For MPI control relay location, see MPI CONTROL RELAY LOCATION table.

MPI CONTROL RELAY LOCATION

Scheme 35

1. This step checks ignition switch supply voltage of control relay. Disconnect control relay connector. Turn ignition on. Using DVOM, measure voltage between terminal No. 8 of relay harness connector and vehicle ground. (Scheme 35) If voltage is battery voltage, go to step 2. If voltage is not battery voltage, check and repair circuit between ignition switch and control relay.
2. This step checks continuity of control relay ground circuit. Turn ignition off. Using DVOM, check continuity between control relay harness connector terminal No. 6 and vehicle ground. If continuity exists, go to step 3. If continuity does not exist, check and repair circuit between control relay and vehicle ground.
3. This step checks battery supply voltage of control relay. Using DVOM, measure voltage between terminal No. 4 of relay harness connector and vehicle ground. If voltage is battery voltage, go to step 4. If voltage is not battery voltage, check and repair circuit between battery and control relay.
4. This step checks continuity of circuit between control relay and ECM. Disconnect ECM connector. Using DVOM, check continuity between control relay harness connector terminal No. 3 and ECM connector terminals No. 12 and 25. (Scheme 34)and (Scheme 35). If continuity exists, go to step 5. If continuity does not exist, check and repair circuits between control relay harness connector and ECM.
5. This step checks supply voltage to control relay actuator. Connect ECM and MPI control relay connectors. Using DVOM, backprobe control relay terminal No. 2. With engine cranking, voltage should be 8 volts or greater. Start engine and run at 2500 RPM or greater. If voltage is battery voltage, harness is okay. If voltage is not battery voltage, go to step 6.
6. If control relay tests okay in steps 6 through 8, replace ECM. Removal of relay may assist in testing. Continuity should exist between terminals No. 5 and 7. Measure resistance between terminals No. 6 and 8. Continuity should exist in only one direction. Replace control relay if continuity is not as specified.
7. Connect 12-volt power source between relay terminals No. 5 and 7. Connect positive lead to terminal No. 7. With relay energized, battery voltage should exist between terminals No. 1 and 5. With power source removed, voltage should not exist.
8. Move 12-volt power source to relay terminals No. 6 and 8. Connect positive lead to terminal No. 8. With relay energized, continuity should exist between terminals No. 2 and 4 and between terminals No. 3and 4. With power source removed, continuity should not exist. Replace control relay if measurements are not as specified.

FUEL DELIVERY

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

Fuel Injectors

See TESTS W/CODES article in this section.

IDLE AIR CONTROL (IAC) MOTOR

Note. For diagnosis and testing information concerning IAC motor position sensor, see TESTS W/CODES article in this section.

Scheme 36

1. Using a stethoscope, listen for operating sound of IAC motor when ignition switch is placed in ON position. If no operating sound can be heard, proceed with following tests.
2. This step checks for continuity between IAC motor and ECM. Disconnect IAC motor harness connector and ECM harness connector. Connect a jumper wire between ECM harness connector terminal No. 4 and vehicle ground. (Scheme 34) Using DVOM, check continuity between IAC harness connector No. 5 and vehicle ground. (Scheme 36)
3. Move jumper wire to ECM harness connector terminal No. 17 and vehicle ground. Using DVOM, check continuity between IAC harness connector No. 6 and vehicle ground. If continuity does not exist, check and repair appropriate circuit. If continuity exists, go to step 4.
4. If preceding tests do not show any system or component malfunction and ECM is suspected, replace ECM and retest system.

IDLE SPEED CONTROL MOTOR

Note. For diagnosis and testing information concerning ISC motor position sensor, see TESTS W/CODES article in this section.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article in this section.

See TESTS W/CODES article in this section.

See TESTS W/CODES article in this section.

Knock Sensor

See TESTS W/CODES article in this section.

EXHAUST GAS RECIRCULATION (EGR)

See TESTS W/CODES article in this section.

Purge Control Solenoid Valve

1. Label and disconnect both vacuum hoses from solenoid valve. Disconnect electrical connector. Connect hand vacuum pump to solenoid valve nipple where Red-striped hose was connected. Apply vacuum to solenoid valve. Vacuum should hold.
2. Apply battery voltage to terminals of solenoid valve. Vacuum should bleed down when voltage is applied to terminals. Using an ohmmeter, check resistance across solenoid valve terminals. Reading should be 36-44 ohms at 68°F (20°C). If reading is not within specification, replace valve.
3. This step checks voltage at purge solenoid. Disconnect purge solenoid harness connector. Turn ignition on. Using DVOM, measure voltage at harness connector terminal No. 2 (vertical terminal). If voltage is battery voltage, go to step 4. If voltage is not battery voltage, check and repair circuit between purge solenoid and MPI control relay.
4. This step checks continuity between ECM and purge solenoid. Disconnect ECM harness connector. Connect jumper wire between ECM terminal and vehicle ground. See «ECM TERMINAL ID»(/mitsubishi/mirage/iv-1991-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.
5. Using DVOM, check for continuity between purge solenoid harness connector terminal No. 1 (horizontal terminal) and vehicle ground. If continuity exists, harness is good. If continuity does not exist, check and repair circuit.
6. If preceding tests do not show any system or component malfunction and ECM is suspected, replace ECM and retest system. ECM TERMINAL ID Application Terminal Number All Models 9

PCV Valve

Remove PCV valve. Shake valve by hand. Valve should rattle if moving freely. Apply air pressure to valve. Air should flow in one direction only. Connect PCV valve to vacuum hose and start engine. Ensure vacuum is flowing through valve.

MISCELLANEOUS CONTROLS

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

A/C Switch & Compressor Clutch Relay

Using DVOM, measure power supply voltage of ECM. Disconnect ECM connector. Turn A/C switch and ignition switch to ON positions. Measure voltage between specified ECM terminals and vehicle ground. See A/C POWER ECM TERMINAL LOCATION table. Voltage should be 6 volts or greater. If voltage is not battery voltage, check and repair circuit.

A/C POWER ECM TERMINAL LOCATION

See also:
• BASIC TESTING
• TESTS W/CODES
• WIRING DIAGRAMS
• ENGINE CONTROL MODULE (ECM) LOCATION
• RELAYS