1987 MAZDA 626 check engine

CONTROL SYSTEM 4C
Resistance
Check resistance between the terminals with an
ohmmeter.
Between terminals Resistance (Q)
1B « 1D More than approx. 20
2F <- 1C More than approx. 60
2F « 1A oo
2B « 2D More than approx. 60
2B ~ 2C oo
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. Reconnect 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. Reconnect the switch connector.
Note
Refer to Section 6 for replacement of the
clutch switch.
P/S PRESSURE SWITCH
Inspection
1. Disconnect the P/S pressure switch connector.
2. Connect an ohmmeter to the switch.
3. Start the engine. Check continuity of the switch
while turning the steering wheel at idle.
P/S Continuity
Turning Yes
Not turning No
4. Reconnect the switch connector.
Note
Refer to Section 10 for replacement of the P/S
pressure switch.
4C-97

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

4C CONTROL SYSTEM
E/L CONTROL UNIT
Inspection
1. Connect a voltmeter between the E/L control unit
and a ground.
2. Start the engine and check the terminal voltages
as described below.
76G04C-180
Terminal Input Output Connection to Voltage (after warm-up) Remarks Terminal Input Output Connection to Ignition switch: ON Idle Remarks
A
(BW) — — Ignition switch Approx. 12V
B — — — — — —
C
(B) — — Ground OV
D (LY) O Electrical fan relay Approx. 12V Coolant temp.: below 97°C (207°F) D (LY) O Electrical fan relay
Below 1,5V Coolant temp.:
above 97°C (207°F)
E (GY) Control unit (11) OV E/L: ON E (GY) Control unit (11)
Approx. 12V E/L: OFF
F (W) O Headlight switch Approx. 12V Headlight switch:
ON F (W) O Headlight switch
Below 1,5V Headlight switch:
OFF
G (LB) o Blower motor switch Below 1.5V Blower motor switch: ON (3rd or 4th position) G (LB) o Blower motor switch
Approx. 5V Others
H
(BL) o Rear defroster
switch
Below 1.5 V Rear defroster
switch: ON H
(BL) o Rear defroster
switch Approx. 12V Rear defroster switch: OFF
76G04C-181
Replacement
1. Replace the E/L control unit.
2. Install in the reverse order of removal.
76G04C-182
4C—102

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

CONTROL SYSTEM 4C
WATER THERMO SENSOR
Inspection
1. Remove the water thermo sensor.
76G04C-199
86U04A-203
2. Place the sensor in water with a thermometer and
heat the water gradually.
3. Check resistance of the sensor with an ohmmeter.
Coolant Resistance
-20°C ( —4°F) 14.5—17.8 kfl
20°C ( 68°F) 2.2-2.7 kQ
40°C (104°F) 1.0—1.3 kQ
60°C (140°F) 500—640 O
80°C (176°F) 280—350 fl
4. If not correct, replace the water thermo sensor.
OXYGEN SENSOR
Inspection of Output Voltage
1. Warm up the engine and run it at idle.
2. Disconnect the oxygen sensor connector.
3. Connect a voltmeter between the oxygen sensor
and a ground.
4. Run the engine at 4,500 rpm until the voltmeter
indicates approx. 0.7V.
76G04C-200
5. Increase and decrease the engine speed suddenly
several times. Check to see that when the speed
is increased the meter reads between 0.5V—1 .OV,
and when the speed is decreased it reads between
OV—0.4V.
6. If the voltmeter dosen't indicate as specified, re-
place the oxygen sensor.
86U04A-206
4C—107

4C CONTROL SYSTEM
Check connector: Green (6 pin)

cable
49 H018 9A1
Inspection of Sensitivity
1. Warm up the engine to the normal operating tem-
perature and run it at idle.
2. Connect the SST to the check connector.
Note
Digital code checker (49 G018 9A0) can be
used.
76G04C-213
Increase the engine speed to between 2,000 and
3,000 rpm, and check that the monitor lamp flash-
es for 10 seconds.
Monitor lamp: Flashes ON and OFF
more than 8 times/10 sec
86U04A-208
A B C D
/llkw^ - ®
I « ^
76G04C-201
4C—108
DISTRIBUTOR
On-vehicle Inspection
1. Remove the rubber boot from the distributor con-
nector.
2. Run the engine at idle.
3. Check terminal voltage with a voltmeter.
Terminal Voltaae
A (G signal) 1.0—2.4
B (Ne sianaB 1.8—2.2
C (Power supply) Approx. 12V
D (Ground) OV
4. If not correct, check the wiring harness for an open
or short circuit, then check the distributor for G sig-
nal or Ne signal.