Engine Controls - System/component Tests: Other Mazda 626 GD

TURBOCHARGER AIR BY-PASS VALVE

Remove air by-pass valve. Connect vacuum pump to port "A" of valve. Apply vacuum to port "A" and compressed air to port "B". (Scheme 53) Verify air flows through valve with prescribed vacuum applied to port "A". See AIR BY-PASS VALVE VACUUM SPECIFICATION table. Replace air by-pass valve if it does not operate as indicated.

AIR BY-PASS VALVE VACUUM SPECIFICATIONS

Scheme 53

TURBOCHARGER BOOST PRESSURE

Engine must be cool. Disconnect hose "A" from solenoid valve and connect pressure gauge. (Scheme 54) Warm engine to normal operating temperature. Increase engine speed to 4000 RPM and verify boost pressure is more than zero psi. If boost pressure is not to specification, proceed to following tests as necessary.

Scheme 54

TURBOCHARGER COMPRESSOR & TURBINE WHEEL DEFLECTION

Allow engine to cool. Disconnect negative battery cable. Remove air funnel. Turn compressor and turbine wheel. Replace turbocharger if wheel does not turn freely or if wheel touches housing.

INTERCOOLER

Remove intercooler. Inspect for cracks, restriction or damage and replace if necessary.

TURBOCHARGER OVERBOOST WARNING

Start engine and run at 2000 RPM. Lift air cleaner upper case and push measuring plate completely open. Warning buzzer should sound and engine speed should drop or engine should stall.

TURBOCHARGER SOLENOID VALVE

Disconnect small air tube from air hose. Disconnect solenoid valve connector. (Scheme 55) Blow through air tube and verify air does not flow. If air does flow, replace solenoid valve and turbocharger as an assembly. Apply 12 volts and ground to solenoid valve connector. Blow through air tube and verify air does pass. If air does not pass with 12 volts applied, replace solenoid valve and turbocharger as an assembly.

Scheme 55

TURBOCHARGER WASTEGATE

1. Engine must be cool. Remove exhaust manifold insulator and side insulator. Remove hose connected to actuator and connect compressed air source with pressure gauge. (Scheme 56)
2. Apply compressed air to actuator. Apply 8.5 psi (0.6 kg/cm 2 ) on MX-6 and 626. Verify actuator rod moves when connecting and disconnecting hose supplying compressed air.

Scheme 56

A/C SWITCH

See A/C CUT-OUT SYSTEM under FUEL CONTROL.

BRAKE LIGHT SWITCH

Disconnect brake light switch connector. Measure resistance between terminals of brake light switch. With brake pedal released, resistance should be infinite. With brake pedal depressed, resistance should be zero ohms.

CLUTCH SWITCH (M/T)

Remove connector from switch. Connect ohmmeter to switch terminals. Check continuity exists with clutch pedal depressed and no continuity exists with pedal released. Replace switch if continuity is not correct.

COOLANT TEMPERATURE SWITCH

1. Remove both switches from radiator hose flange. (Scheme 57) Place each switch individually in container of engine oil with thermometer. Heat engine oil slowly and check for continuity of switch with an ohmmeter.
2. Continuity should be present in switch No. 1 at temperatures greater than 207°F (97°C). Continuity should be present in switch No. 2 at temperatures greater than 226°F (108°C). Replace switch(s) if not operating as described.

Note. DO NOT heat engine oil above 248°F (120°C).

Scheme 57

COOLANT THERMOSENSOR

1. Remove thermosensor. Place thermosensor in container of heated coolant with thermometer.
2. Connect ohmmeter to thermosensor terminals. Note resistance at specified temperatures. See appropriate «COOLANT THERMOSENSOR RESISTANCE»(ref-18174-S12150367642000123000000) table. Replace if not within specification.

COOLANT THERMOSENSOR RESISTANCE

CRANK ANGLE SENSOR

See IGNITION TESTING in BASIC TESTING article.

EGR POSITION SENSOR

For testing procedures, see EGR SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

IDLE SWITCH

Unplug idle switch connector. Check continuity between switch and ground. See IDLE SWITCH CONTINUITY table. (Scheme 58) If switch does not pass test, check harness for open or short circuits. Replace idle switch if necessary. On MX-6 and 626, if idle switch needs replacing, entire throttle body must be replaced.

IDLE SWITCH CONTINUITY

Scheme 58

KNOCK SENSOR

See KNOCK CONTROL under IGNITION SYSTEM.

THROTTLE POSITION SENSOR

See ADJUSTMENTS article for checking and adjustment procedures.

VEHICLE SPEED SENSOR

See PIN VOLTAGE CHART S and SENSOR RANGE CHARTS articles.

CIRCUIT OPENING RELAY

See FUEL CONTROL CIRCUIT in BASIC TESTING article for test procedures.

MAIN RELAY

1. Ensure main relay clicks when ignition is turned on and off.
2. If no sound is heard, unplug relay. Apply 12 volts to terminal "A" and ground terminal "B". (Scheme 59)
3. Use ohmmeter to check terminal continuity. Terminals "C" and "D" should have continuity with 12 volts applied. There should be no continuity with no voltage applied. If relay does not respond as described, replace main relay.

Scheme 59

AIR INDUCTION CONTROL SOLENOID

For all related control solenoids, see AIR INDUCTION SYSTEMS.

AIR INJECTION SOLENOIDS

For all related control solenoids, see AIR INJECTION under EMISSION SYSTEMS & SUB-SYSTEMS.

EGR SOLENOID

For testing procedures, see EGR SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

FUEL INJECTORS

Using stethoscope, listen for normal clicking sound at each injector during idle and acceleration. If clicking sound is not heard, check injector wiring circuit or main relay and circuit.

FUEL INJECTOR RESISTANCE

Remove electrical connector from injector. Using ohmmeter, measure resistance between injector terminals. Replace injector if resistance is not within specifications.

FUEL INJECTOR RESISTANCE

PRESSURE REGULATOR CONTROL SOLENOID

1. Unplug vacuum hose from pressure regulator control solenoid. Blow through solenoid from port "A". Ensure air flows through port "B". (Scheme 60)
2. Unplug solenoid valve connector. Connect 12 volts and ground to solenoid terminals. Blow through solenoid from port "A". Air should exhaust through valve air filter. Replace solenoid valve if it does not pass test.

Scheme 60

PURGE CONTROL SOLENOID

For testing procedures, see FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS.

WASTEGATE SOLENOID

See AIR INDUCTION SYSTEMS.

FUEL DELIVERY

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

Fuel Pump Relay Control

See FUEL SYSTEM in BASIC TESTING article.

INJECTOR FUEL LEAKAGE

1. Relieve fuel system pressure. See BASIC TESTING article. Remove air valve or dynamic chamber, if necessary. Remove delivery pipe with hoses still connected. Remove fuel injectors. Using wire, secure injectors tightly onto delivery pipe. CAUTION: Ensure injectors are securely tied to delivery pipe. If not properly secured, fuel may spray from loose connections.
2. Install a jumper wire between terminals of Yellow fuel pump check connector. Fuel pump check connector is located on firewall, under windshield wiper motor.
3. Turn ignition on for 10 seconds. Turn ignition off and clean injector nozzles. On 4-cylinder models, tilt injectors approximately 60 degrees. On all models, turn ignition on. Check that no fuel leakage exists at injectors. After one minute, a drop of fuel leakage is acceptable. If fuel leakage is excessive, replace faulty injector.

INJECTOR DELIVERY VOLUME

1. With delivery pipe and injectors removed, secure injectors tightly onto delivery pipe with wire. Install hose on injector. Install Injector Checker (49 B092 953) on injector. (Scheme 61)
2. Install jumper between 2 terminals of fuel pump test circuit connector. See BASIC TESTING article for test connector location. Turn ignition on. Connect injector checker to battery voltage. Note injector volume after 15 seconds.
3. Replace injectors which do not meet volume specifications. See INJECTOR VOLUME SPECIFICATIONS table. Check primary and secondary injectors in the same manner.

INJECTOR VOLUME SPECIFICATIONS

Scheme 61

PULSATION DAMPER

Start engine and run at idle. Pulsation damper is located at end of fuel rail. Place finger over pulsation damper and ensure damper pulsates. Replace pulsation damper if pulsations are not felt.

AIR VALVE

1. Remove air valve from throttle body. Blow air through valve from port "A" and ensure air comes out port "B" when valve is cold. (Scheme 62)
2. Place air valve in hot water (greater than 176°F or 80°C) for one minute. Blow air through valve from port "A". No air should come out of port "B". Replace valve if not functioning as specified.

ISC VALVE

Measure resistance of Idle Speed Control (ISC) valve at 2-wire connector. See ISC RESISTANCE SPECIFICATIONS table. If not to specification, replace ISC valve.

ISC RESISTANCE SPECIFICATIONS

Scheme 62

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article.

KNOCK CONTROL (TURBO MODELS)

1. Connect Self-Diagnostic Checker (49 H018 9A1) and ground test connector lead. Turn ignition on.
2. Tap lightly on right engine hanger with plastic hammer. Ensure monitor lamp on checker flashes. If not, connect a known good sensor and recheck.
3. If test results remain the same, replace knock control unit.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For complete vacuum schematics, see VACUUM DIAGRAMS article.

DECELERATION CONTROL SYSTEM

Note. On all models, the deceleration control system is a function of dashpot and ECU. Dashpot prevents sudden closure of throttle valve. ECU controls fuel cut-off during deceleration. For adjustment and testing, see ADJUSTMENTS article.

EGR CONTROL VALVE

Bring engine to normal operating temperature and run at idle. Disconnect and plug vacuum hose at EGR control valve. Engine should run smoothly. Connect vacuum pump to EGR control valve and apply more than 2.36 in. Hg. Engine should run rough or stop. If not, clean or replace EGR control valve.

EGR MODULATOR VALVE (FEDERAL NON-TURBO)

Remove EGR modulator valve. Plug No. 1 port and connect a vacuum pump to No. 3 port. (Scheme 63) Blow into exhaust gas port. Operate vacuum pump and verify vacuum is held. Release exhaust port and verify vacuum is released.

Scheme 63

EGR POSITION SENSOR (EXCEPT FEDERAL NON-TURBO)

1. Backprobe EGR position sensor connector with voltmeter. (Scheme 64)
2. With EGR vacuum hose disconnected, connect vacuum pump to the EGR valve. Turn ignition on and check voltages at connector. Use EGR POSITION SENSOR VOLTAGE table to compare results.
3. If voltage is not correct at terminals A and B, check wiring harness and connection at ECU connector terminals 2A and 2C. If voltage is not correct at terminal C, check sensor resistance, harness and ECU connector terminal 2F.
4. Check sensor resistance according to «EGR POSITION SENSOR RESISTANCE»(ref-18174-S11177614482000123000000) table. If resistance is not within specifications, replace sensor.

EGR POSITION SENSOR VOLTAGE

EGR POSITION SENSOR RESISTANCE

Scheme 64

EGR SOLENOID (FEDERAL NON-TURBO)

1. Disconnect vacuum hose from solenoid. (Scheme 65) Blow through port "A". Ensure air exhausts through port "B".
2. Disconnect 2 wire connector from solenoid. Connect 12 volts to one terminal and ground other terminal of solenoid. Blow air through port "A". Ensure air exhausts through air filter.

Scheme 65

EGR SOLENOID (EXCEPT FEDERAL NON-TURBO)

1. Disconnect vacuum hoses and blow through vent hose. (Scheme 66) Ensure air flows. Disconnect solenoid connector.
2. Apply 12 volts to White/Blue wire ("B" terminal) of solenoid and ground both Red/Black wires ("A" and "C" terminals) of solenoid. Blow through vent hose and ensure air does not flow. Replace solenoid if not okay.
3. Blow through vacuum hose and ensure air does not flow. Apply 12 volts to Blue/White wire connector of solenoid and ground both Red/Black wire connectors of solenoid. Blow through vacuum hose and ensure air does flow. Replace solenoid if not okay.

Scheme 66

EVAPORATION LINE

Disconnect hose leading from charcoal canister to fuel tank and connect a vacuum pump to the hose. Apply vacuum and note if vacuum is held. No vacuum should be held. If vacuum is held, test check valve, cut-valve and evaporation hose for blockage.

CHECK VALVE

Note direction of valve installation. Remove check valve. Blow air into both ends of valve. Air should flow through valve from charcoal canister side, but should not flow from airflow meter side (beveled end). Replace valve if defective.

CHECK & CUT VALVE

1. Remove check and cut valve. Connect a pressure gauge with "T" fitting to check and cut valve nipple leading to fuel tank. Cap the opposite nipple. (Scheme 67)
2. Blow through passage "A". When pressure gauge reads.14-.71 psi (.01-.05 kg/cm 2 ), valve should open. Remove "T" fitting and pressure gauge. Connect "T" fitting to bottom of valve. Blow through passage "B". When pressure gauge reads.78-1.0 psi (.06-.07 kg/cm 2 ), valve should open. Replace assembly if valve did not open at specified pressure.

Scheme 67

PURGE CONTROL SOLENOID VALVE

To check purge control solenoid valve, remove hoses from charcoal canister. Attempt to blow through intake manifold port. Air should not pass. If air can be blown through solenoid valve, disconnect the solenoid valve connector and connect 12 volts and a ground to solenoid valve terminals. Blow through check valve, air should flow through valve. If not, replace valve. (Scheme 68)

Scheme 68