Egi Control System Mazda MX-6 V

DESCRIPTION

The Mazda Electronic Gas Injection (EGI) computerized engine control system monitors various engine/vehicle functions to control engine operation and lower emissions while maintaining good fuel economy and driveability. (Scheme 25)and (Scheme 26).

The Electronic Control Unit (ECU), through various input sensors, monitors battery voltage, engine RPM, amount of intake air, cranking signal, crankshaft angle, intake temperature, radiator and engine coolant temperatures, oxygen concentration in exhaust gases, throttle opening, atmospheric pressure, gearshift lever position, clutch engagement, braking, power steering operation, and A/C compressor operation. The ECU uses all input information to control spark timing, fuel injection, and output devices.

The ECU has a built-in fail-safe mechanism. If a fault occurs while driving, the ECU will substitute pre-programmed values. Driving performance will be affected, but the vehicle may still be driven.

Scheme 25

Scheme 26

Air Conditioning Switch

Closes when A/C or blower is in the "ON" position.

Airflow Meter (Inlet Air Temperature)

Varies voltage signal to ECU in relation to inlet air temperature.

Airflow Meter (Vc)

Corrected airflow meter voltage.

Airflow Meter (Vs)

Airflow position signal.

Atmospheric Pressure Sensor

Varies voltage signal according to altitude.

Brake Light Switch

Signals ECU of vehicle braking condition.

Coolant Temperature Sensor

Varies input voltage signal according to engine coolant temperature.

Coolant Temperature Switch

Switch opens and closes according to radiator temperature.

Electrical Load Control

Signals ECU of additional electrical load.

Idle Switch

Indicates throttle closed position.

Ignition Coil

Signals engine speed.

Ignition Switch

Supplies battery voltage to ECU during engine cranking.

Inhibitor Switch (A/T)

Signals ECU of gear selection.

Knock Sensor

Signals ECU of knocking condition.

Main Relay

Provides battery voltage to ECU.

Neutral/Clutch Switch (M/T)

Signals ECU of clutch operation and transaxle gear selection.

Oxygen (O2) Sensor

Generates voltage signal depending on oxygen content of exhaust.

Power Steering Switch

Provides signal to ECU when vehicle is turning.

Speed Sensor

Signals ECU of vehicle speed. Located in speedometer.

Throttle Position Sensor (TPS)

Provides voltage signal in response to throttle position.

Air Conditioning Relay

ECU completes ground circuit for A/C operation.

"Check Engine" Light

Lights during engine start up and monitored component malfunction. Is also referred to as MIL or Malfunction Indicator Light. Is used to read trouble codes.

EGR Solenoid

ECU completes ground circuit to control vacuum to EGR valve.

Fuel Injectors

ECU completes ground circuit to control fuel injector pulse.

Idle Speed Control Valve

Is part of By-Pass Air Control (BAC) valve attached to throttle body. ECU intermittently completes ground to idle speed control valve for proper idle RPM.

Knock Control Unit

Retards timing during knock condition.

Pressure Regulator Control Solenoid

ECU completes ground circuit to control vacuum to fuel pressure regulator.

Purge Control Solenoid

ECU completes ground circuit to control vacuum to canister purge.

Voltage Reference

Provides 4.5-5.5 volts to TPS and atmospheric pressure sensor.

Hard Start or No Start (Cranks Okay)

Incorrect fuel injection or pressure. Poor connections at airflow meter or throttle body. Electronic Spark Advance (ESA) Control system (turbo only).

Engine Stalls Cold

Air valve or idle speed control valve malfunction. EGR control valve stuck open. Incorrect fuel injection or pressure. Poor connections at airflow meter or throttle body.

Engine Stalls Warm

PCV system clogged. Air valve or idle speed control valve malfunction. EGR control valve stuck open. Incorrect fuel injection or pressure. Poor connections at airflow meter or throttle body.

Rough Idle Cold

Air valve or idle speed control valve malfunction. PCV system clogged. EGR control valve stuck open. Incorrect fuel injection or pressure. Poor connections at airflow meter or throttle body.

Rough Idle Warm

PCV system clogged. Air valve or idle speed control valve malfunction. EGR control valve stuck open. No. 1 purge valve malfunction. Incorrect fuel injection or pressure. Poor connections at airflow meter or throttle body.

High Idle Speed

Air valve or idle speed control valve malfunction. Poor connection at airflow meter or throttle body.

Poor Acceleration, Hesitation or Lack of Power

EGR control valve stuck open. No. 1 purge valve malfunction. Poor connections at airflow meter or throttle body. Exhaust system clogged. Incorrect fuel injection or pressure. Turbo system malfunction.

Runs Rough on Deceleration

Fuel-cut system malfunction. Air valve or idle speed control valve malfunction.

High Fuel Consumption

Fuel-cut system malfunction. Incorrect fuel injection or pressure. EGR control valve stuck open. Exhaust system clogged.

Engine Stalls or Rough After Hot Start

Pressure regulator control system malfunction. Incorrect fuel injection or pressure.

Excessive Oil Consumption

Turbo system malfunction.

Knocking (Turbo Only)

ESA malfunction. Incorrect fuel injection or pressure.

Abnormal Noise or Vibration

Turbo system malfunction.

Fails Emission Test

Exhaust system clogged. EGR control valve stuck open. Fuel-cut system malfunction. Air valve or idle speed control valve malfunction. No. 1 purge valve malfunction. Poor connections at airflow meter or throttle body. Incorrect fuel injection or pressure.

Trouble Code Access

1. Connect Self-Diagnostic Checker (49 H018 9A1 ) to Green 6 pin connector and negative battery terminal. (Scheme 27) Connector is located at back of left front wheelwell. Select position "A" on checker.
2. Ground Green 1-pin connector with jumper wire. With ignition on and engine stopped, verify code 88 flashes and buzzer sounds for 3 seconds. If okay, go to step 3). If code 88 does not flash, check main relay, power circuit or harness connections. If code 88 does flash and buzzer sounds continuously for more than 20 seconds, replace ECU and retest.
3. Note codes. Check TROUBLE CODE IDENTIFICATION for possible cause. (Scheme 28)and (Scheme 29).

Scheme 27

Clearing Trouble Codes

1. Disconnect negative battery cable. Depress brake pedal for at least 5 seconds. Reconnect battery cable.
2. With Self-Diagnostic Checker (49 H018 9A1 ) connected, ground test connector with jumper wire. Turn ignition on, but do not start engine for 6 seconds.
3. Start engine and run at 2000 RPM for 2 minutes. Verify no codes are displayed.

1. Using jumper wire, ground Green 1-pin connector. Connector is located at back of left front wheelwell.
2. With ignition on and engine stopped, observe "Check Engine" or MIL light. Note trouble codes. Check TROUBLE CODE IDENTIFICATION for possible cause. (Scheme 28)and (Scheme 29). If light remains on continuously, ECU is defective.

1. Disconnect negative battery cable. Depress brake pedal for at least 5 seconds. Reconnect battery cable.
2. Ground test connector with jumper wire. Turn ignition on, but do not start engine for 6 seconds.
3. Start engine and run at 2000 RPM for 2 minutes. Verify no codes are displayed.

Trouble Code I.D. (1 of 2). Scheme 28

Trouble Code I.D. (2 of 2). Scheme 29

Code 01, Ignition Pulse. Scheme 30

Code 08, Air Flow Meter. Scheme 31

Code 09, Water Thermo Sensor. Scheme 32

Code 10, Intake Air Thermo Sensor. Scheme 33

Code 12, Throttle Sensor. Scheme 34

Code 14, Atmospheric Pressure Sensor. Scheme 35

Code 15, Oxygen Sensor. Scheme 36

Code 17, Feedback System. Scheme 37

Code 25, Solenoid Valve - Pressure Regulator. Scheme 38

Code 26, Solenoid Valve - Purge. Scheme 39

Code 28, Solenoid Valve - EGR. Scheme 40

Code 34, Solenoid Valve - Idle Speed Control Valve (ISC). Scheme 41

Code 01, Ignition Pulse. Scheme 42

Code 02, Ne Signal. Scheme 43

Code 03, G1 Signal. Scheme 44

Code 04, G2 Signal. Scheme 45

Code 05, Knock Sensor & Knock Control Unit. Scheme 46

Code 08, Air Flow Meter. Scheme 47

Code 09, Water Thermo Sensor. Scheme 48

Code 10, Intake Air Thermo Sensor. Scheme 49

Code 12, Throttle Sensor. Scheme 50

Code 14, Atmospheric Pressure Sensor. Scheme 51

Code 15, Oxygen Sensor. Scheme 52

Code 16, EGR Position Sensor. Scheme 53

Code 17, Feedback System. Scheme 54

Code 25, Solenoid Valve - Pressure Regulator. Scheme 55

Code 26, Solenoid Valve - Purge. Scheme 56

Code 28, Solenoid Valve - EGR, Vacuum Side. Scheme 57

Code 29, Solenoid Valve - EGR, Vent Side. Scheme 58

Code 34, Solenoid Valve - Idle Speed Control Valve (ISC). Scheme 59

Code 42, Solenoid Valve - Waste Gate. Scheme 60

With Engine Signal Monitor

1. Connect Engine Signal Monitor (49 9200 162 ) with Adapter Harness (49 9200 163 ). (Scheme 61) Check voltage by selecting terminal number on monitor.
2. Compare readings with ECU TERMINAL VOLTAGE charts. If voltage is not correct, inspect harness connections and components.

Scheme 61

With Analog Voltmeter

1. Ground negative lead. Backprobe each specific ECU connector terminal to monitor voltage.
2. Compare readings with ECU TERMINAL VOLTAGE charts. If voltage is not correct, inspect harness connections and components.

Non-Turbo ECU Terminal Voltage (1 of 3). Scheme 62

Non-Turbo ECU Terminal Voltage (2 of 3). Scheme 63

Non-Turbo ECU Terminal Voltage (3 of 3). Scheme 64

Non-Turbo ECU Terminal Identification. Scheme 65

Turbo ECU Terminal Voltage (1 of 3). Scheme 66

Turbo ECU Terminal Voltage (2 of 3). Scheme 67

Turbo ECU Terminal Voltage (3 of 3). Scheme 68

Turbo ECU Terminal Identification. Scheme 69

DECELERATION CONTROL SYSTEM

Deceleration control system is a function of ECU. It provides fuel cut during deceleration.

1. Connect Engine Signal Monitor (49 9200 162) or backprobe ECU connector terminals No. 3C or 3E. Start engine. Voltage should pulsate.
2. Increase engine speed to 4000 RPM. Suddenly decrease engine speed. Voltage should become constant during deceleration. If not, check idle switch, coolant temperature switch and all ECU connections.

Airflow Meter

Inspect airflow meter for damage and ensure measuring plate moves smoothly. Disconnect airflow meter connector. (Scheme 70) Measure resistance using AIRFLOW METER TERMINAL RESISTANCE table.

Scheme 70

AIRFLOW METER TERMINAL RESISTANCE

1. Connect voltmeter to terminal D. Turn ignition on and note voltage. (Scheme 71)
2. Voltage at sea level should be 3.5-4.5 volts. Voltage at 6500 feet should be 2.5-3.5 volts. Replace if not to specification.

Scheme 71

1. Disconnect brake light switch connector. Measure resistance between Green/White wire and White/Green wire terminals of brake light switch.
2. With brake pedal released, resistance should be infinite. With brake pedal depressed, resistance should be zero ohms.

By-Pass Air Control (BAC) Valve

1. Remove BAC valve from throttle body. (Scheme 72) Blow air through port "A". Ensure air exhausts through port "B" when valve is cold. If not, replace BAC valve.
2. Measure resistance of Idle Speed Control (ISC) valve at 2 wire connector of BAC valve. Resistance should be between 6.3-9.9 ohms, at normal operating temperature. If not, replace BAC valve.

Scheme 72

Scheme 73

Scheme 74

1. Remove circuit opening relay from fuse block panel. (Scheme 73) Check circuit opening relay circuits with «CIRCUIT OPENING RELAY TERMINAL CIRCUITS»(/mazda/mx-6/v-1986-1991/remont/testing-diagnostics/#egi-control-system) table. CIRCUIT OPENING RELAY TERMINAL CIRCUITS Terminal Condition Specifications Fp Resistance to Ground 0.2-30 Ohms Fc Resistance to Ground (Cranking) Infinite B Voltage to Ground (Ign. On) Battery Voltage STA Voltage to Ground (Cranking) Approx. 9 Volts E1 Resistance to Ground Infinite
2. With circuit opening relay removed, apply 12 volts to terminal STA of relay. (Scheme 74) Ground terminal E1. Ensure continuity from relay terminals B to FP.
3. Apply 12 volts to terminal B of relay. Ground terminal Fc. Ensure battery voltage is at relay terminal Fp.
4. Ensure that relay has correct resistance between terminal with «CIRCUIT OPENING RELAY RESISTANCE»(/mazda/mx-6/v-1986-1991/remont/testing-diagnostics/#egi-control-system) table.

CIRCUIT OPENING RELAY RESISTANCE

Clutch Switch (M/T)

1. Disconnect clutch switch connector. Measure resistance across Red/Green wire and Light Green/Black wire terminals on switch.
2. With clutch pedal released, resistance should be zero ohms. With clutch pedal depressed, resistance should be infinite.

Disconnect and remove coolant temperature sensor. Check resistance using COOLANT TEMPERATURE SENSOR RESISTANCE table.

COOLANT TEMPERATURE SENSOR RESISTANCE

Remove switch from radiator. Switch should have continuity at temperatures greater than 63°F (17°C).

Scheme 75

1. If adapter is available, disconnect EGR position sensor connector and connect Adapter (49 G018 901 ) in harness. (Scheme 75) If adapter is not available, back probe connector with voltmeter.
2. With EGR vacuum hose disconnected, connect vacuum pump. Turn ignition on and check voltages at connector. Use «EGR POSITION SENSOR VOLTAGE»(/mazda/mx-6/v-1986-1991/remont/testing-diagnostics/#egi-control-system) table to compare results. EGR POSITION SENSOR VOLTAGE Terminal Voltage A 4.5-5.5 B Less Than 1.5 C (Without Vacuum).25-.95 C (With Vacuum) Approx. 4
3. If voltage is not correct at terminals A and B, check harness and connection at ECU connector terminals No. 2A and 2C. If voltage is not correct at terminal C, check sensor resistance, harness and ECU connector terminal No. 2F.
4. Check sensor resistance according to «EGR POSITION SENSOR RESISTANCE»(/mazda/mx-6/v-1986-1991/remont/testing-diagnostics/#egi-control-system) table. If resistance is not within specifications, replace sensor.

EGR POSITION SENSOR RESISTANCE

EGR Solenoid (Non-Turbo)

1. Disconnect vacuum hose from solenoid. (Scheme 76) 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 though port "A". Ensure air exhausts through air filter.

Scheme 76

EGR Solenoid (Turbo)

1. Disconnect vacuum hoses and blow through vent hose. (Scheme 77) Ensure air flows. Disconnect solenoid connector.
2. Apply 12 volts to White/Blue wire connector of solenoid and ground both Red/Black wire connectors 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 77

Electrical Load Control Unit

1. Connect a voltmeter between control unit and ground. Start engine. Check voltage at terminals using ELECTRONIC CONTROL UNIT VOLTAGE CHART. (Scheme 78)

Electronic Control Unit Voltage Chart. Scheme 78

1. Disconnect 1-pin connector at idle switch. Check for continuity between switch and ground.
2. With throttle fully closed, there should be continuity. With throttle open, there should be no continuity. If switch is not correct, replace throttle body.

1. Disconnect White 3-pin connector near battery. Measure resistance between Black/Yellow wire and Black/Red wire.
2. With selector lever in "P" or "N", resistance should be zero ohms. With selector lever in any other position, resistance should be infinite.

Knock Control System (Turbo Only)

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

1. Ensure a clicking sound is heard at main relay when turning ignition on and off. (Scheme 79) Disconnect main relay. Apply 12 volts to terminal A and ground terminal B.
2. Ensure there is continuity between main relay terminals C and D, when voltage is applied. There should be no continuity when voltage is not applied.

Scheme 79

Neutral Switch (M/T)

1. Disconnect Black 3-pin connector (only 2 wires) behind battery. Measure resistance between Black wire and ground. If resistance is zero ohms, use other side of connector.
2. Place transaxle in neutral position. Resistance between the Red/Green wire and Black wire should be infinite.
3. Place transaxle in any gear. Resistance between Red/Green wire and Black wire should be zero ohms.

1. Disconnect power steering connector at power steering gear. Connect an ohmmeter to switch.
2. Start engine. When turning, resistance should be zero ohms. When not turning, resistance should be infinite.

1. Disconnect vacuum hose from solenoid. 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 the other terminal of solenoid. Blow air though port "A". Ensure air exhausts through air filter.

Purge Solenoid

1. Disconnect vacuum hose from solenoid. (Scheme 80) Blow through port "A". Ensure air exhausts through air filter.
2. Disconnect 2 wire connector from solenoid. Connect 12 volts to one terminal and ground the other terminal of solenoid. Blow air though port "A". Ensure air exhausts through port "B".

Scheme 80

Wastegate Solenoid (Turbo Only)

1. Disconnect small air tube from air hose. (Scheme 81) Disconnect solenoid connector. Blow air though air tube, ensure air does not flow. If not okay, replace turbo and solenoid as an assembly.
2. Apply 12 volts to one side of solenoid and ground the other. Blow air through air tube, ensure air does flow. If not, replace turbo and solenoid as an assembly.

Scheme 81

5th Gear Switch (M/T)

1. Disconnect White 2-pin connector near battery. Measure resistance between Blue wires.
2. With transaxle in 5th gear, resistance should be infinite. With transaxle in any other gear, resistance should be zero ohms.

Wiring Diagram for MX-6 & 626 EGI Non-Turbo. Scheme 82

Wiring Diagram for MX-6 & 626 EGI Turbo. Scheme 83

See also:
• AIRFLOW METER TERMINAL RESISTANCE