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

System Check (2.5L)

Connect tachometer to IG terminal of diagnostic connector. (Scheme 77) Start engine, and operate at idle. Manually open throttle valve. Ensure shutter valve actuator rods No. 1 and 2 retract at specified RPM. See VRIS RPM SPECIFICATIONS table. (Scheme 78) If necessary, check Variable Resonance Induction System (VRIS) components.

Scheme 77

VRIS RPM SPECIFICATIONS

Scheme 78

Check Valve

Remove check valve. Blow air through port "A" and verify flow through port "B". Ensure air does not flow in reverse direction. Replace as necessary.

Shutter Valve Actuators (2.5L)

Disconnect vacuum hose from shutter valve actuators No. 1 and 2. (Scheme 78) Connect vacuum pump to actuator. (Scheme 79) Apply vacuum to each actuator separately and verify shutter valve rod retracts. Replace actuator as necessary.

Solenoid Valve

Disconnect vacuum hose from solenoid valve port "A". Blow air through port "B". (Scheme 79) Ensure air flows from valve air filter. Disconnect solenoid valve connector, and connect 12 volts and a ground to solenoid valve terminals. Blow air through valve port "B", and ensure air flows from port "A". Replace solenoid valve as necessary.

Scheme 79

Vacuum Chamber

Remove vacuum chamber. Visually inspect chamber for clogging, cracks and damage. Replace as necessary.

Scheme 80

POWERTRAIN CONTROL MODULE

1. Locate Electronic Control Unit (ECU) or Powertrain Control Module (PCME). See ECU/PCME LOCATION table. Connect Engine Signal Monitor (49-9200-162) to ECU/PCME. (Scheme 81) Check voltage at each terminal of ECU/PCME. If input and output component voltage readings are not as specified, check faulty component. See «PIN VOLTAGE CHARTS»(ref-18368) article, appropriate G - TESTS W/ CODES article below, and testing for appropriate component in this article. «TESTS W/CODES - 2.0L A/T»(ref-18325) (for MX-6) «TESTS W/CODES - 2.5L»(ref-18326) (for MX-6) «TESTS W/CODES - 2.0L A/T»(ref-18327) (for 626) «TESTS W/CODES - 2.5L»(ref-18328) (for 626)
2. If input and output component voltages are as specified and ECU/PCME voltage is incorrect, replace ECU/PCME.

ECU/PCME LOCATION

Scheme 81

A/C SWITCH

See A/C CUT-OFF CONTROL SYSTEM under A/C CLUTCH under MISCELLANEOUS CONTROLS.

2.0L

Remove sensor from air cleaner housing. With sensor disconnected, measure resistance between sensor terminals. See ACT SENSOR RESISTANCE table. Replace sensor as necessary.

ACT SENSOR RESISTANCE

1. Pull rubber boot back from airflow sensor connector. Backprobe sensor connector, and check terminal voltages. (Scheme 82) See «AIRFLOW SENSOR TERMINAL VOLTAGES»(ref-18357-S14523479022000123000000) table.
2. If voltages are not correct, check wiring for open or short.

Note. Airflow sensors on 2.0L models do not have burn-off operation.

AIRFLOW SENSOR TERMINAL VOLTAGES

Scheme 82

2.5L

Inspect airflow meter for damage, and ensure measuring plate or cone moves smoothly. (Scheme 83) Disconnect airflow meter electrical connector. Move measuring plate or cone, and measure resistance between terminals. See appropriate AIRFLOW METER TERMINAL RESISTANCE table. Replace sensor as necessary.

AIRFLOW METER TERMINAL RESISTANCE

Scheme 83

ATMOSPHERIC PRESSURE SENSOR

See PIN VOLTAGE CHARTS article in the ENGINE PERFORMANCE section. On 2.0L A/T, see TROUBLE CODE CHART 14 in appropriate G - 2.0L A/T TESTS W/ CODES article in the ENGINE PERFORMANCE section below.

1. «TESTS W/CODES - 2.0L A/T»(ref-18325) (for MX-6)
2. «TESTS W/CODES - 2.0L A/T»(ref-18327) (for 626)

BRAKELIGHT SWITCH

Disconnect brakelight switch connector. Measure resistance between terminals of brakelight switch. With brake pedal released, continuity should not exist. With brake pedal depressed, continuity should be present. Replace switch as necessary.

CLUTCH SWITCH (M/T)

Disconnect clutch switch electrical connector. Using ohmmeter, check continuity between switch terminals. With clutch pedal depressed, continuity should be present. With clutch pedal released, continuity should not exist. Replace switch as necessary.

CRANK ANGLE SENSOR

See IGNITION CHECKS in BASIC TESTING article in the ENGINE PERFORMANCE section.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Remove engine coolant temperature sensor. Place sensor and thermometer in container of coolant. Connect ohmmeter to sensor terminals. Slowly heat coolant. Note resistance at specified temperatures. See appropriate ECT SENSOR RESISTANCE table. Replace sensor as necessary.

ECT SENSOR RESISTANCE

EGR POSITION SENSOR

See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS.

HEATED OXYGEN SENSOR (HO2S)

With engine at room temperature, disconnect HO2S connector. Measure resistance across terminals "A" and "B" on 2.0L, or "C" and "D" on 2.5L. (Scheme 84) See HO2S RESISTANCE table. Replace HO2S as necessary. Also see PIN VOLTAGE CHARTS article in the ENGINE PERFORMANCE section.

HO2S RESISTANCE

Scheme 84

1. Disconnect idle switch electrical connector. (Scheme 85) Check continuity between switch and ground. Continuity should be present with throttle valve fully closed. Continuity should not exist with throttle valve open.
2. If continuity is not as specified, check wiring harness for open or short circuits. On 2.0L, replace idle switch and throttle body as an assembly if wiring harness is okay.

Idle switch is part of throttle position sensor. See ADJUSTMENTS article in the ENGINE PERFORMANCE section.

Scheme 85

INHIBITOR SWITCH (A/T)

Disconnect inhibitor switch electrical connector. Connect ohmmeter to indicated switch terminals. (Scheme 86)and (Scheme 87). Continuity should be present with gearshift in Park and Neutral positions. Continuity should not exist in any other gear positions. Replace switch as necessary.

Scheme 86

Scheme 87

KNOCK SENSOR

See PIN VOLTAGE CHARTS article in the ENGINE PERFORMANCE section.

NEUTRAL SWITCH

Disconnect neutral switch electrical connector. Using ohmmeter, check continuity between switch terminals. Ensure continuity exists with transmission in Neutral. Continuity should not exist with transmission in any other gear. Replace switch as necessary.

OXYGEN (O2S) SENSOR

1. Warm engine to operating temperature. Operate engine at idle. Disconnect O2S sensor electrical connector. Connect voltmeter between O2S sensor connector terminals "C" and "D" on 2.5L, or terminals "A" and "B" on 2.0L. (Scheme 88)
2. Observe voltmeter while rapidly accelerating and decelerating engine speed. Voltage should be 0.5-1.0 volt during acceleration and 0.0-0.4 volt during deceleration. Replace O2S sensor as necessary.

Scheme 88

POWER STEERING PRESSURE SWITCH (PSPS)

Disconnect power steering pressure switch electrical connector. Connect ohmmeter to PSPS terminals. Start engine, and operate it at idle. Turn steering wheel from side to side, and observe ohmmeter. Ohmmeter should indicate continuity when front wheels are turned. Continuity should not exist when wheels are not turned. Replace switch as necessary.

THROTTLE POSITION SENSOR

See ADJUSTMENTS article in the ENGINE PERFORMANCE section for checking and adjustment procedures.

VEHICLE SPEED SENSOR (VSS)

See PIN VOLTAGE CHARTS article in the ENGINE PERFORMANCE section.

Circuit Opening Relay

See FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article in the ENGINE PERFORMANCE section.

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 89)
3. Using ohmmeter, check continuity between terminals "C" and "D". Continuity should be present with 12 volts applied. Continuity should not exist with no voltage applied. Replace main relay as necessary.

Scheme 89

EGR Solenoid

See EXHAUST GAS RECIRCULATION (EGR) 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

Disconnect fuel injector electrical connector. Using ohmmeter, measure resistance between injector terminals. Resistance should be 12-16 ohms. Replace injector as necessary.

Pressure Regulator Control Solenoid

Disconnect vacuum hose from pressure regulator control solenoid. Blow air through solenoid port "A". (Scheme 90) Ensure air flows through port "B". Disconnect solenoid valve electrical connector. Connect 12 volts and ground to solenoid terminals. Blow air through solenoid port "A". Air should flow through valve air filter. Replace solenoid as necessary.

Scheme 90

Purge Control Solenoid

See FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS.

VRIS Solenoid (2.5L)

See VARIABLE RESONANCE INDUCTION SYSTEM (2.5L) under AIR INDUCTION SYSTEMS.

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC TESTING article in the ENGINE PERFORMANCE section.

See FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article in the ENGINE PERFORMANCE section.

Fuel Pump Circuit

See FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article in the ENGINE PERFORMANCE section.

Fuel Pressure Regulator

See FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article in the ENGINE PERFORMANCE section.

Pressure Regulator Control

1. Engine must be at or near operating temperature. Turn engine off. Disconnect vacuum hose at fuel pressure regulator and connect a vacuum gauge to hose.
2. Without touching throttle, start engine. Observe vacuum gauge. Vacuum should not exist. If vacuum is present, check pressure regulator control solenoid and related circuits. If no vacuum exists, count seconds until vacuum gauge shows intake manifold vacuum. See «PRESSURE REGULATOR SPECIFICATION»(ref-18357-S35970215922000123000000) table.
3. If vacuum gauge shows intake manifold vacuum after specified amount of time, system is okay. (Scheme 91) If intake manifold vacuum is not present, check vacuum source, pressure regulator control solenoid and related circuits.

See PRESSURE REGULATOR CONTROL SOLENOID under SOLENOIDS under RELAYS & SOLENOIDS.

Scheme 91

PRESSURE REGULATOR SPECIFICATION

See FUEL INJECTORS under SOLENOIDS under RELAYS & SOLENOIDS.

Injector Fuel Leakage

1. Relieve fuel system pressure. See «BASIC TESTING»(ref-18324) article in the ENGINE PERFORMANCE section. Remove air valve or dynamic chamber as 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 injectors are not properly secured to delivery pipe, fuel may spray from loose connections.
2. Connect a jumper wire between terminals F/P and GND of diagnostic connector located near battery. (Scheme 92)
3. Turn ignition on for 10 seconds. Turn ignition off, and clean injector nozzles. On 4-cylinder models, tilt injectors about 60 degrees. On all models, turn ignition on. Ensure no fuel leakage exists at injectors. After one minute, a single drop of fuel is acceptable. If fuel leakage is present, replace faulty injector.

Scheme 92

Air Valve (2.0L)

1. Remove air valve from throttle body. Blow air through valve from port "A" and ensure air comes out of port "B" when valve is cold. (Scheme 93)
2. Place air valve in water at temperature greater than 176°F (80°C) for one minute. Blow air through valve from port "A". No air should come out of port "B". Replace valve as necessary.

Air Valve System

Connect jumper wire between diagnostic connector terminals TEN and GND. Connect tachometer to diagnostic connector terminal IG. (Scheme 94) Start engine. Idle speed should decrease as engine reaches normal operating temperature. Replace valve as necessary.

ISC Valve

Disconnect ISC valve electrical connector. Connect ohmmeter to ISC valve 2-wire connector. Measure resistance. See ISC RESISTANCE SPECIFICATIONS table. If resistance is not within specification, replace ISC valve.

ISC RESISTANCE SPECIFICATIONS

Scheme 93

Scheme 94

IGNITION SYSTEM

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

DECELERATION CONTROL SYSTEM

Note. Deceleration control system is a function of dashpot and ECU. Dashpot prevents sudden closure of throttle valve. ECU controls fuel cut during deceleration. For adjustment and testing, see ADJUSTMENTS article in the ENGINE PERFORMANCE section.

1. Connect Engine Signal Monitor (49-9200-162) and Test Harness (49 G018 903) to ECU. Start engine. Increase engine speed, and check voltage at ECU terminals 3O and 3P while engine is cold. See «PIN VOLTAGE CHARTS»(ref-18368) article in the ENGINE PERFORMANCE section. Voltage should be 12 volts.
2. Warm engine to operating temperature, and operate it at idle. Increase engine speed, and ensure engine signal monitor Green and Red lights flash at ECU terminals 3O and 3P.
3. Disconnect EGR solenoid valve (vacuum side) electrical connector. Apply 12 volts and a ground to solenoid valve. Ensure engine runs rough or stalls at idle. Test EGR components as necessary. (Scheme 95)

System Check (2.0L)

Check all connectors and hose routings. Check for cracks, leakage and restrictions, and repair as necessary. Start engine, and ensure diaphragm of EGR control valve does not move while engine is cold. Warm engine to operating temperature and operate at idle. Increase engine speed to about 2000 RPM, and ensure diaphragm of EGR control valve moves. If no movement is detected, test EGR components as necessary. (Scheme 96)

Scheme 95

Scheme 96

EGR Control Valve

Bring engine to normal operating temperature and operate at idle. Disconnect and plug vacuum hose at EGR control valve. Engine should run smoothly. Connect vacuum pump to EGR control valve, and apply vacuum. See EGR CONTROL VALVE OPERATING VACUUM table. Engine should run rough or stall. If engine does not operate as specified, clean or replace EGR control valve.

EGR CONTROL VALVE OPERATING VACUUM

EGR Modulator Valve (2.0L)

Remove EGR modulator valve. Plug port No. 3, and connect a vacuum pump to port No. 1. (Scheme 96)and (Scheme 97). Blow into exhaust gas port. Operate vacuum pump and verify vacuum is held. Release exhaust port and verify vacuum is released. Replace EGR modulator valve if it does not test as described.

Scheme 97

EGR Position Sensor (2.0L)

Disconnect EGR position sensor electrical connector. Check resistance across terminals. (Scheme 98) At room temperature, resistance should be 182-336 ohms. If resistance is not as specified, replace EGR control valve.

Scheme 98

EGR Position Sensor (2.5L)

1. Disconnect ECU electrical connector. Connect Engine Signal Monitor (49-9200-162) and Test Harness (49 G018 903) between ECU and wiring harness. Disconnect vacuum hose from EGR control valve. Connect vacuum pump to EGR control valve.
2. Turn ignition on. Check voltage at adapter harness connector terminals. (Scheme 99) See «EGR POSITION SENSOR VOLTAGE»(ref-18357-S17802907612000123000000) table.
3. If voltage is not correct at terminals "A" and "B", check wiring harness and connection at ECU connector terminals 2J and 3C. If voltage is not correct at terminal "C", check sensor resistance, wiring harness and ECU connector terminal 2I.
4. Disconnect EGR position sensor electrical connector. Disconnect vacuum hose from EGR control valve. Apply vacuum to EGR control valve.
5. Check sensor resistance between indicated terminals. See «EGR POSITION SENSOR RESISTANCE»(ref-18357-S24603618842000123000000) table. If resistance is not within specifications, replace sensor.

EGR POSITION SENSOR VOLTAGE

EGR POSITION SENSOR RESISTANCE

Scheme 99

EGR Solenoid Valve (2.5L)

1. Disconnect vacuum hoses. Blow air through vacuum hose (vacuum side). Ensure air does not flow. Disconnect EGR solenoid valve (vacuum side) electrical connector. Apply 12 volts and a ground to solenoid valve (vacuum side) terminals. (Scheme 100) Blow air through vacuum hose and ensure air flows.
2. Blow air through vacuum hose (vent side). Ensure air flows. Disconnect EGR solenoid valve (vent side) electrical connector. Apply 12 volts and a ground to solenoid valve (vent side) terminals. (Scheme 100) Blow air through vacuum hose and ensure air does not flow. Replace solenoid valves as necessary.

Scheme 100

Charcoal Canister

Check for loose, missing, cracked and broken connections and parts. Repair or replace as necessary. No liquid should exist in canister.

2-Way Check Valve

Remove check valve. Connect a vacuum pump to one end of check valve. Air should flow with about 1-1.7 in. Hg applied. Connect vacuum pump to other end of check valve. Air should also flow with about 1-1.7 in. Hg applied. Replace valve as necessary.

Fuel Vapor Valve

Remove fuel vapor valve. Blow air into upper port of valve. Air should flow through valve to lower port. Turn valve upside down. Blow air through lower port of valve. Air should not flow. Replace valve as necessary.

Purge Control Solenoid Valve

1. Warm engine to normal operating temperature and operate at idle. Disconnect vacuum hoses from solenoid valve. Ensure vacuum is not present at solenoid valve. Disconnect vacuum hoses from charcoal canister.
2. Ensure air does not flow through solenoid valve. If air flows through solenoid valve, disconnect solenoid valve connector. Connect 12 volts and a ground to solenoid valve terminals. (Scheme 101) Blow air through check valve. Air should flow through valve. Replace valve as necessary.

Separator

Check for loose, missing, cracked and broken connections and parts. Repair or replace as necessary. No liquid should exist in canister.

Scheme 101

A/C Cut-Off Control System

1. Turn A/C, blower and ignition on. DO NOT start engine. Shift transmission into a drive gear. Open throttle fully. Listen for A/C clutch disengaging and re-engaging after a few seconds. See «A/C CUT-OFF TIME SPECIFICATIONS»(ref-18357-S42937683632000123000000) table.
2. If system does not function as specified, check operation of related switches, sensors and relays. See «PIN VOLTAGE CHARTS»(ref-18368) article in the ENGINE PERFORMANCE section.

A/C CUT-OFF TIME SPECIFICATIONS