wiring MAZDA 626 1987 Service Manual

DECELERATION CONTROL SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remarks
Engine control unit Detects signals from input sensors and switches; cuts fuel injection
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit ON at idle
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
76G04C-135
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensor or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to page 4C—10 and 11.)
Possible cause Water thermo sensor System inspection
Page 4C—107 4C—74
Checking order 2 1
76G04C-136
4C-73

4C DECELERATION CONTROL SYSTEM
System Inspection (Electrical Signal)
1. Connect the SST between the wiring harness and
control unit.
2. Set 3C, 3E 3F, or 3H position on the SST.
Note
3C — For No. 2 injector
3E — For No. 1 injector
3F — For No. 4 injector
3H — For No. 3 injector
76G04C-137
3. Check that the indicator lamps alternately flash at
idle.
86U04A-125
0-6V 0-20V
® $
4. Increase the engine speed to 4,000 rpm, then sud-
denly decrease the engine speed.
5. Check that the green indicator lamp is OFF dur-
ing deceleration.
6. Accelerate and check that the voltage decreases.
76G04C-138
4C—74

4C ESA CONTROL SYSTEM
COMPONENT DESCRIPTION
Component Function Remark
Air flow sensor Detects amount of intake air;
sends signal to engine control unit
Distributor Has Ne and G signal pick-up and distributes high voltage to spark plugs
Engine control unit Detects signals from input sensors and switches; decides best ignition timing
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit Installed on throttle body
Igniter Receives spark signal from engine control unit and generates high voltage in ignition coil
Ignition switch
(ST position) Sends engine cranking signal to engine con-trol unit
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Knock sensor (leaded fuel) Detects engine knocking; sends signal to knock control unit
Throttle sensor Detects throttle opening angle; sends signal to engine control unit Installed on throttle body
76G04C-140
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switches.
Note
If no problem is found, continue with inspection of the next system of the troubleshooting
Guide. (Refer to page 4C—10 and 11)
Possible cause
Page
Symptom
Air flow sensor Igniter Engine control
unit terminal Knock sensor Possible cause
Page
Symptom
Air flow sensor Igniter
1X
Knock sensor Possible cause
Page
Symptom
4C—103 Refer to section 5 4C—98 4C—109
Hard start or won't start (Cranks OK) 3 1 2 —
Knocking — 1
76G04C-141
4C-76

4C EGR SYSTEM (UNLEADED FUEL)
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible cause
Throttle
sensor
Solenoid valve
(EGR)
EGR
modula-
tor valve
EGR con-trol valve
Water
thermo
sensor
Water
thermo switch
Engine control unit
terminal
System in-spection
2N
Page 4C—104 4C—78 4C—79 4C—79 4C—107 4C—106 4C—98 4C—78
Checking order 8 2 4 3 6 5 7 1
76G04C-144
System Inspection
1. Start the engine.
2. Accelerate the engine while still cold and verify that
the diaphragm of the EGR control valve does not
move.
3. Warm up the engine to normal operating temper-
ature and run it at idle.
Warning
Be careful when checking the EGR control
valve, the surrounding area is very hot.
4. Accelerate the engine and check that the di-
aphragm of the EGR control valve moves.
Solenoid Valve (EGR)
1. Disconnect the vacuum hose from the vacuum
pipe.
2. Blow through the solenoid valve from vacuum hose
A.
3. Check that air flows from port B.
76G04C-146
4C-78

EEC SYSTEM
4C

TROUBLESHOOTING
Check
the
condition
of the
wiring harness
and
connectors before checking
the
sensors
or
switches.
Note
Make
the
system inspection first.
If no
problem
is
found, continue with inspection
of the

next system
of the
Troubleshooting Guide. (Refer
to
pages 4C—10
and 11.)

Possible cause
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Solenoid
valve
(No.
1 purge
control)

Solenoid

valve
(No.
2 purge
control)

Two-way

check
valve

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Engine
control
unit
terminal

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Solenoid
valve
(No.
1 purge
control)

Solenoid

valve
(No.
2 purge
control)

Two-way

check
valve

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£
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Page 4C—83 4C-84 4C-84 4C—84 4C-83 4C-85 4C-82 4C-83 4C-106 4C-107 4C—98 4C-81
Checking order (Unleaded fuel) 4 2 3 — 10 11 5 6 7 8 9 1
Checking order
(Leaded fuel) — — — 1 — 2
76G04C-152
System Inspection
1. Check
the
vacuum hose routing.
2. If there
is a
poor connection, clog,
or
leak, repair
or replace
as
necessary.
3. Warm
up the
engine
and run it at
idle.
4. Disconnect vacuum hose
A
from
No. 1
purge con-
trol valve
and
connect
the SST to the
hose.
86U04A-140
5. Increase
the
engine speed
to
above 2,500
rpm

and verify that
the
gauge shows more than
150

mmHg
(5.9
inHg).
6. If not correct, check the solenoid valve (No.
1
purge
control).
7. Reconnect hose
A to No. 1
purge control valve.
4C-81
76G04C-153

4C CONTROL SYSTEM
ENGINE CONTROL UNIT
Engine Signal Monitor (49 9200 162) and Adapter (49 9200 163).
Adapter harness 49 9200 163
Engine wiring harness^
Selector switch
' —
Monitor switch
49 9200 162
Control unit terminal number
Terminals (A and B)
Q IIIM«I
76G04C-178
The Engine Signal Monitor (49 9200 162) is used to check the control unit terminal voltages.
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.
4C—98

CONTROL SYSTEM 4C
Terminal Voltage
If the input and output devices wiring are normal, but the engine control unit terminal voltage is incor-
rect, replace the engine control unit.
Terminal Input Output Connection to Voltage (After warming-up) Remark Terminal Input Output Connection to Ign: ON Idle Remark
1A — — — — — —
1B o Self-Diagnosis Checker (Code No.)
For 3sec. after ignition switch OFF ->• ON: below 2.5V (Buzzer sounds) After 3sec.: approx. 12V (Buzzer does not sound)
• Using Self-Diagnosis Check-er and test con-nector grounded • Buzzer sounds: below 2.5V • Buzzer does not sound: approx. 12V
1C o
Solenoid valve (Variable inertia control) Approx. 12V
Above 5200 rpm (Unleaded fuel) or 5400 rpm (Leaded fuel): Below 2.5V
1D o Self-Diagnosis Checker (Monitor lamp)
For 3sec.after igni-tion switch OFF -» ON:
approx. 5V (light il-luminates)
After 3sec.: approx. 12V (light does not illuminate)
(Test connector grounded) approx. 5V (Test connector not grounded) Monitor lamp ON: approx. 5V Monitor lamp OFF: approx. 12V
With Self-Diagnosis
Checker
1E O Idle switch Accelerator pedal released: OV
Accelerator pedal depressed: approx. 12V
1F o A/C relay A/C switch ON: below 2.5V
A/C switch OFF: approx. 12V Blower motor ON
1G O Neutral or clutch switch
In-gear condition Clutch pedal depressed: approx. 12V Clutch pedal released: OV
MTX (Neutral: con-stant approx. 12V)
1H
(U/F) o Water thermo
switch
Approx. 12V Radiator temp.: be-low 17°C (63°R 1H
(U/F) o Water thermo
switch OV Radiator temp.:
above 17°C (63°F)
11 o Electrical load control unit E/L switch ON: below 2.5V
E/L switch OFF: approx. 10—12V
Electrical load: Rear defroster switch
Headlight switch Blower motor switch (3rd & 4th position) Electrical fan switch
1J — — — — —
1K o P/S pressure
switch
Constant approx.
12V
P/S ON: below 2.5V P/S OFF: approx. 12V
1L o A/C switch A/C switch ON: below 2.5V A/C switch OFF: aDDrox. 12V Blower motor: ON
1M o Distributor
(Ne signal) OV or 5V Approx. 2.0V
1N o Distributor (G signal) OV or 5V Approx. 1.2V
Note
Terminals labeled "U/F" are only for unleaded fuel.
4C-99

CONTROL SYSTEM 4C
AIR FLOW SENSOR
Visual Inspection
1. Remove the air hose.
2. Check the air flow sensor visually for the following:
a) Torn protection net (air cleaner side)
76G04C-183
b) Restricted protection net
76G04C-184
Output Voltage Inspection
1. Remove the rubber boot from the air flow sensor
connector.
2. Check terminal voltage with a voltmeter.
——^.Condition Terminal — ... Ign. switch;ON Engine running
A (Idle mixture) 0—5V
B (Power supply) Approx. 12V
C (Burn-off) OV
D (Air flow mass) 1.0-1,6V I 1.7V-5V
E (Ground) OV
F (Ground) 0V
6. If not correct, check the wiring harness for an open
or short circuit
7. If the wiring harness is OK, replace the air flow
sensor.
76G04C-185
4C-103

4C CONTROL SYSTEM
Jjf (Terminal A)
n PI
WRED r^j
BLACK
BLACK 1 (Terminal C)
76G04C-189
Replacement
1. Disconnect the connector.
2. Loosen the air hose clamps.
3. Replace the air flow sensor.
Caution
Install the air flow sensor so that the arrow on
the sensor aligns with air flow direction.
4. Tighten the hose clamps.
5. Reconnect the connector to the sensor.
THROTTLE SENSOR
Caution
Use a precision voltmeter with a scale of 0.01V
to inspect or adjust the throttle sensor. If it
is not available, replace the throttle sensor
and throttle body as an assembly.
Inspection
1. Disconnect the throttle sensor connector (3-pin).
2. Connect the SST between the throttle sensor and
the wiring harness.
3. Turn the ignition switch ON.
4. Measure BLACK and RED wire voltages.
Specifications:
BLACK—Approx. OV
RED—4.5—5.5V
5. If not correct, check the battery voltage and wir-
ing harness. If these are OK, replace the engine
control unit.
6. Using the RED wire voltage as a guide, find the
specified BLUE wire voltage ranges in the table.
RED wire voltage
Specified range (V) RED wire voltage Fully close Fully open
4.90—4.99V 0.40-0.58 3.90-4.60
5.00—5.09V 0.41—0.60 3.97-4.70
5.10-5.19V 0.42—0.61 4.05—4.79
4C-104

4C CONTROL SYSTEM
4. Make sure that the throttle valve is fully closed.
5. Turn the throttle sensor so that the BLUE wire volt-
age indicates within the specified closed range.
6. Tighten the throttle sensor mounting screw.
7. Recheck that the BLUE wire voltage is within the
specified range.
76G04C-195
8. Turn the ignition switch OFF.
9. Disconnect the SST and reconnect the throttle sen-
sor connector.
10. Disconnect the negative battery terminal and de-
press the brake pedal for 5 seconds to eliminate
the from the malfunction memory from the control
unit.
76G04C-196
76G04C-198
4C-106
IDLE SWITCH
Inspection
1. Disconnect the idle switch connector.
2. Check continuity between the switch and a ground.
Throttle valve condition Continuity
Fully closed Yes
Open No
3. If not correct, check condition of the wiring harness
of the idle switch. Replace the idle switch and throt-
tle body as an assembly, if necessary.
WATER THERMO SWITCH
Inspection
1. Remove the switch from the radiator.
2. Place the switch in water with a thermometer and
heat the water gradually.
3. Check for continuity of the switch with an
ohmmeter.
Coolant temp. Continuity
More than approx. 17°C (63°F) Yes
Less than approx. 10°C (63°F) No
4. If not correct, replace the water thermo switch.