1987 MAZDA 626 Workshop Manual

CONTROL SYSTEM 4B
CONTROL SYSTEM
Atmospheric
pressue sensor
Engine control unit
Brake light switch
Clutch switch
Circuti opening
relay
E/L control unit
Air flow meter
Neutral switch
76G04B-129
The control system consists of the input devices and the engine control unit. The engine control unit
controls the fuel injection amount (EGI), fuel injection pressure, bypass air amount, switch monitor func-
tion, and fail-safe function.
4B—83

4B CONTROL SYSTEM
RELATIONSHIP CHART
Input Devices and Output Devices
BRAKE LIGHT SWITCH O X X X X X X X X X
ELECTRICAL LOAD CONTROL UNIT X X X X X X X X O X
P/S PRESSURE SWITCH* X X X X X X X X O X
A/C SWITCH O X X X X O O X X O
IGNITION SWITCH
(STA

POSITION) O O X O X X X X O O
INHIBITOR SWITCH o X X X O X X X X O
NEUTRAL
AND
CLUTCH SWITCH o X X X X X X X X O
OXYGEN SENSOR o X X X X X X X X X
WATER THERMO SWITCH (RADIATOR) o X X X O X X X X X
ATMOSPHERIC PRESSURE SENSOR o X X X X O X O O X
INTAKE
AIR
THERMO SENSOR o X X O X X X O O X
WATER THERMO SENSOR o X X O O O X X o X
IDLE SWITCH o o X O X X X X o X
THROTTLE SENSOR o O X X O X X X X O
AIR FLOW METER o X X X X O X X X X
IGNITION COIL o O X O O O X X o O

INPUT
DEVICES
OUTPUT
DEVICES
FUEL
INJECTION
AMOUNT FUEL
INJECTION

TIMING
PRESSURE
REGULATOR
EGR
PURGE
IDLE-UP
(A)*
IDLE-UP
(B)

IDLE-UP

(C)

rr

INPUT
DEVICES
OUTPUT
DEVICES
INJECTOR
AIR

VALVE
SOLENOID
VALVE
AIR

BYPASS
SOLENOID
VALVE
AIR

CONDITIONEI

76G04B-108
4B-84

CONTROL SYSTEM 4B
Output Devices and Engine Conditions
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76G04B-109
4B-85

4B CONTROL SYSTEM
69G04A-161
86U04A-169
76G04B-130
EGI MAIN FUSE
Inspection
Check the continuity of EGI main fuse.
MAIN RELAY
1. Check that a "clicking" sound is heard at the main
relay when turning the ignition switch ON and OFF.
2. Apply 12V and a ground to (A) and (B) terminals
of the main relay.
3. Check continuity at terminals using an ohmmeter.
-Operation
Terminals 12V Not applied 12V Applied
©- ® No continuity Continuity
CIRCUIT OPENING RELAY
Relay Circuit
1. Remove the circuit opening relay.
2. Check the circuit as described.
Terminal Checkina item Correct result
FD Resistance 0.2-300
Fc Continuity (crankinnl oo
B Voltaae (Ian: ON) Batterv voltaae
STA Voltaae (Crankincri Approx. 9V
Ei Continuity oo
Circuit Opening Relay
Apply 12V and a ground to the terminals below and
check the circuit opening relay as described.
12V Grounded Correct result
STA Ei B FP: Continuity
B Fc Fp: Battery voltage
Resistance
Check the resistance between the terminals using an
ohmmeter.
69G04A-164
Between terminals Resistance (Q)
STA <- E1 15-30
B
<-<•
Fc 80-150
B « Fp 00
4B—86

CONTROL SYSTEM 4B
ENGINE CONTROL UNIT
Engine Signal Monitor (49 9200 162) and Adapter (49 9200 163).
Adapter harness 49 9200 163
Engine wiring harnessN
Selector switch
Monitor switch
Engine control unit
terminal number
Terminals
(A and 8)
ENGINE SIGNAL MONITOR
86U04A-171
The Engine Signal Monitor (49 9200 162) was developed to check the control unit terminal voltages.
This monitor easily inspects the individual terminal voltages through selection of the monitor switch.
How to Use the Engine Signal Monitor
1. Connect the Engine Signal Monitor (49 9200 162) between the engine control unit and the en-
gine harness using the adapter (49 9200 163).
2. Turn the selector switch and monitor switch to select the terminal number.
3. Check the terminal voltage.
Caution
Never apply voltage to terminals A and B.
4B-87

4B CONTROL SYSTEM
Terminal Voltage
If the input and output devices and related wiring are normal, but the engine control unit terminal volt-
age is incorrect, replace the engine control unit.
Terminal Input Output Connection to Voltage (After warming-up) Remarks Terminal Input Output Connection to IGN: ON Idle Remarks
1A — — — — —
1B o Self-Diagnosis Checker (Code number)
For 3sec. after ignition switch OFF ->• ON: below 6.2V (Buzzer sounds) After 3sec.: Battery voltage (Buzzer does not sound)
• Using Self-Diagnosis Check-er and test con-nector grounded • Buzzer sounds: below 6.2V • Buzzer does not sound: Battery voltage
1C — — — — —
1D o Self-Diagnosis Checker (Monitor lamp)
Test connector grounded
For 3sec. after igni-tion switch OFF ON:
below 6.2V (light il-luminates) After 3sec.: Battery voltage (light does not illuminate)
(Test connector grounded) approx. 10V (Test connector not grounded) Monitor lamp ON: below 6.2V Monitor lamp OFF: Battery voltage
With Self-Diagnosis
Checker
1E O Idle switch Accelerator pedal released: below 1.5V
Accelerator pedal depressed: Battery voltage
1F o A/C relay A/C switch ON: below 2.5V A/C switch OFF: Battery voltage
Blower motor ON
1G — — — — —
1H o Water thermo switch Below 1,5V Radiator temp.:
above 17°C (63°F)
11 o Electrical load con-trol unit Electrical load ON: below 1.5V Electrical load OFF: Battery voltage Electrical load: Rear defroster Headlight Blower motor (3rd & 4th position) Electrical fan
1J o Brake light switch Brake pedal released: below 1.5V
Brake pedal depressed: battery voltage
1K — — — — — —
1L o A/C switch A/C switch ON: below 1.5V
A/C switch OFF: battery voltage
Blower motor: ON
1M o Ignition coil © terminal Battery voltage *1 Battery voltage *1 Engine Signal Monitor: green and red lights flash
1N — — — — —
10 — — — —
4B-88

CONTROL SYSTEM 4B
Terminal Input Output Connection to Voltage (After warming-up) Remarks Terminal Input Output Connection to IGN: ON Idle Remarks
1P — — — — —
1Q — — — — —
1R — — — — —
1S o Air bypass solenoid valve (Idle-up C) and P/S pressure switch
Battery voltage While solenoid ON (Refer to page 4B—35): below 1.5V
1T — — — — —
1U — — — — —
1V 0 MTX
Neutral and clutch switch
In-gear condition Clutch pedal depressed: battery voltage Clutch pedal released: below 1,5V
Neutral: constant battery voltage
1W O Test connector Test connector grounded: below 1,5V Test connector not grounded: battery voltage Green connector, 1-pin
1X — — — — —
2A o V ref 4.5—5.5V
2B 0 Air flow meter (Vc) 6-10V
2C — — Ground (E2) Approx. OV
2D o Oxygen sensor OV 0-1.OV • Cold engine: 0V at idle • After warming-up: Increase engine speed: 0.5—1.0V Deceleration: 0—0.4V
2E 0 Air flow meter (Vs) Approx. 1.7V Approx. 3—5V Increase engine speed:
voltage increases
2F — -— — —
2G 0 Throttle sensor Accelerator pedal released:
0.4—0.6 V
2H 0 Atmospheric pres-sure sensor At sea level: approx. 4.0V
21 0 Water thermo sensor 0.3—0.6 V Engine coolant temp. 20°C (68°F): approx. 2.5V
2J o Air flow meter (In-
take air thermo
sensor)
Approx. 2.3V at 20°C (68°F)
2K o Solenoid valve (Pres-
sure regulator
control)
For 120 sec. after ignition switch OFF - ON: below 1.5V
For 120 sec. after
starting: below 1.5V
Hot condition: Cool-ant temp, above 70°C (158°F) Intake air temp, above 10°C (50°F)
2K o Solenoid valve (Pres-
sure regulator
control)
Battery voltage Other conditions
2L — — — — —
2M — — —
4B-89

4B CONTROL SYSTEM
Terminal Input Output Connection to Voltage (After warming-up) Remarks Terminal Input Output Connection to IGN: ON Idle Remarks
2N o Solenoid valve (EGR) Below 1,5V • Cold engine: be-low 1,5V Radiator coolant temp.—below 17°C (63°F) or Engine coolant temp.—below 70°C (158°F)
• Engine above ap-prox. 1,500 rpm: Battery voltage
20 o Air bypass solenoid valve (Idle-up B) Battery voltage While solenoid ON (Refer to page 4B-35): below 1.5 V
2P o Solenoid valve
(Purge control valve)
Battery voltage • Medium and high
load: below 1,5V
2Q — — — —
2R — — Ground (E02) Below 1,5V
3A — — Ground (E01) Below 1.5V
3B O Ignition switch (Start position) Below 1,5V While cranking: bat-
tery voltage
3C o Injector (No. 4 and No. 2) Battery voltage *1 Battery voltage *1 Engine Signal Monitor green and red lights flash
3D o Inhibitor switch "N" or "P" range: below 2.0V
Other ranges: battery voltage
ATX
3E o Injector (No. 1 and No. 3) Battery voltage *
1
Battery voltage *1 Engine Signal Monitor: green and red lights flash
3F -— — — —
3G — Ground (Ei) Below 1.5V
3H — — — —
31 o — Ma ri relay Battery voltage
3J — — Battery Battery voltage For back-up
76G04B-110
31 3G 3E 3C 3A
3J 3H 3F 3D 3B
2Q 20 2M 2K 21 2G 2E 2C 2A
2R 2P 2N 2L 2J 2H 2F 2D 2B
1W 1U 1S 1Q 10 1M 1K 11 1G 1E 1C 1A
1X 1V 1T 1R 1P 1N 1L 1J 1H 1F 1D 1B
4B—90