1987 MAZDA 626 brake

DECELERATION CONTROL SYSTEM 4B
COMPONENT DESCRIPTIONS
Component Function Remarks
Brake light switch Detects braking operation (deceleration);
sends signal to engine control unit
Clutch switch Detects in-gear condition;
sends signal to engine control unit Switch ON when clutch pedal released
Dashpot (MTX) Prevents sudden closing of throttle valve during deceleration or shifting Adjustment speed: 1,900—2,100 rpm
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 Installed in throttle sensor
Ignition coil (-) terminal Detects engine speed; sends signal to engine control unit
Neutral switch Detects in-gear condition; sends signal to engine control unit Switch ON when in-gear
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo switch Detects radiator coolant temperature; sends signal to engine control unit ON: above 17°C (63°F)
76G04B-089
4B—65

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

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
Replacement
1. Disconnect the negative battery cable.
2. Remove the front console covers (right and left).
3. Disconnect the connectors from the control unit.
4. Replace the control unit.
NEUTRAL SWITCH
Inspection
1. Disconnect the neutral switch connector.
2. Connect an ohmmeter to the switch.
3. Check continuity of the switch.
Transmission Continuity
In neutral No
In other ranges Yes
4. After checking, connect the switch connector.
Note
Refer to section 7A for replacement of the
neutral switch.
CLUTCH SWITCH
Inspection
1. Disconnect the clutch switch connector.
2. Connect an ohmmeter to the switch.
3. Check continuity of the switch.
Pedal Continuity
Depressed No
Released Yes
4. After checking, connect the switch connector.
Note
Refer to section 6 for replacement of the
clutch switch.
BRAKE LIGHT SWITCH
Inspection
1. Disconnect the brake light switch connector.
2. Connect an ohmmeter to the switch.
3. Check the continuity of the switch.
Pedal Continuity
Depressed Yes
Released No
4. After checking, connect the switch connector.
Note
Refer to section 11 for replacement of the
brake switch.
4B-91

TROUBLESHOOTING GUIDE 4C
TROUBLESHOOTING GUIDE
This troubleshooting guide shows the malfunction numbers and the symptoms of various failures.
Perform troubleshooting as described below.
Input sensors and switches
Possible cause
Page
Symptom and No. CO
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Fault Indicated by SST
Code No. 02 03 05 *i 08 09 11 12 *2 15 • 2 17 *2 25 26 *2 27 *2 28 • 2 34 36 • 2 41
Hard start or won't start
(Cranks OK)
Engine stalls
Rough
Idle
During warm up
After warm up
During warm up
After warm up
High idle speed after warm up
Poor acceleration, hesita-tion or lack of power
TROUBLESHOOTING PROCEDURE
Note
Code No. Is to quickly determine which system or unit may be at fault by use of the SST. (Self-Diagnosis Checker 49 H018 9A1 or Digital Code Checker 49 G018 9A0 with Adaptor harness 49 9200 180)
1st: Check input sensors and output solenoid valves with the SST. (Refer to
page
AC—11.)

2nd: Check other switches with the SST. (Refer to page AC—25.)
3rd: Check the following items:
Electrical system
1) Battery condition 2) Fuses
Runs rough on deceleration
Afterburn in exhaust
system
9
10
Poor fuel consumption
Engine stalls or runs
rough after hot starting
11
12
Knocking
Fuel system
1) Fuel level
2) Fuel leakage 3) Fuel filter 4) Idle speed (with test connec-tor grounded)
Engine
1) Compression 2) Overheating
Ignition system 1) Ignition spark
2) Ignition timing (with test connec-tor grounded)
Intake air system 1) Air cleaner element 2) Vacuum or air leakage 3) Vacuum hose routing 4) Accelerator cable
Others 1) Clutch slippage
2) Brake dragging
Fails emission test 4th: Check Fuel and Emission Control Systems. (Refer to page 4C—10.)
*1..
*2„
.Leaded fuel
.Unleaded fuel
76G04C-009
4C—9

4C TROUBLESHOOTING WITH SST
Check connector: (Green, 6 pin)
49 H018 9A1
86U04A-011
Test connector: (Green, 1 pin)'
INSPECTION PROCEDURE
1. Connect the SST to the check connector. (Green,
6-pin) and the negative battery terminal.
2. Set the select switch to position A.
Note
The check connector is located at the rear of
the left side wheel housing.
3. Ground the test connector (Green, 1-pin) with a
jumper wire.
Note
The test connector is located near the Self-
Diagnosis Checker check connector.
86U04A-012
OO
uu
SELF-DIAGNOSIS CHECKER
MONITOR LAMP SELECT SW «

o o o
o
76G04C-012
4. Turn the ignition switch ON.
5. Verify that 88 flashes on the digital display and that
the buzzer sounds for three seconds after turn-
ing the ignition switch ON.
6. If 88 does not flash, check the control relay (refer
to page 4C—96), power supply circuit, and check
connector wiring.
7. If 88 flashes and the buzzer sounds continuously
for more than 20 seconds check the check con-
nector wiring, then replace the engine control unit
and perform steps 3 and 4 again.
8. Note the code numbers and check for the causes
by referring to the check sequences shown on
pages 4C—16 to 4C—24. Repair as necessary.
Note
Cancel the code numbers by performing the
after-repair procedure after repairing.
AFTER-REPAIR PROCEDURE
1. Cancel the memory of malfunctions by disconnect-
ing the negative battery cable and depress the
brake pedal for at least five seconds.
76G04C-013
4C-12

TROUBLESHOOTING WITH SST 4C
Malfunction display
Sensor or subsystem Self-diagnosis Fail-safe Malfunction
code no. Malfunction code output signal pattern
Sensor or subsystem Self-diagnosis Fail-safe
08
Air flow sensor Open or short circuit Maintains basic sig-nal at preset value
09 o°pNp II IIL •
Water thermo sensor Open or short circuit Maintains constant 35°C (95°F) command
11 0°FNFJUUL
Intake air thermo sensor (dynamic chamber)
Short circuit Maintains constant 20°C (68°F) command
12
Throttle sensor Open or short circuit Maintains constant command of throttle valve fully open
15 ON n
OFF •L 01
Oxygen sensor Sensor output con-tinues less than 0.55V 120 sec. after engine starts (1,500 rpm or over)
Cancels
EG I
feed-
back operation
17 ON n
OFF L HI il
Feedback system Sensor output not changed 20 sec. af-ter engine starts (1,500 rpm or over)
Cancels
EG I
feed-
back operation
25 0°nfJU1LJIL
Solenoid valve (pres-sure regulator control)
Open or short circuit
26 2LMJIL
Solenoid valve (No.1 purge control)
Open or short circuit
27 ON nn
OFF | _ •111
-ii-Solenoid valve (No.2
purge control)
Open or short circuit
28 ON nn
OFF L Hi nr
Solenoid valve (EGR)
Open or short circuit
34 ^jmiHum
Solenoid valve (Idle speed control)
Open or short circuit
36 °FFJMI«U
Oxygen sensor relay
Open or short circuit
41 <£jimjiuM
Solenoid valve (Vari-able inertia control)
Open or short circuit
76G04C-018
Caution
a) If there is more than one failure present, the lowest number malfunction code is dis-
played first, the remaining codes are displayed sequentially.
b) After repairing a failure, turn off the ignition switch and disconnect the negative battery
cable and depress the brake pedal for at least 5 seconds to erase the memory of a mal-
function code.
4C—15