check engine MAZDA 626 1987 Workshop Manual

TROUBLESHOOTING GUIDE 4B
TROUBLESHOOTING GUIDE
This troubleshooting guide shows the malfunction numbers and the symptoms of various failures.
Perform troubleshooting as described below.
Possible cause
Symptom
Input sensors and switches
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4B-14
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4B-16
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4B-17
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4B-18
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4B-19
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4B-20
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4B-21
Output solenoid valves
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4B-22
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4B-23
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4B-23
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4B-23
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4B-24
Fault Indicated by SST
Code No. 01 08 09 10 12 14 15 17 25 26 28 34 35
Hard start or won't start
(Cranks OK)
Engine stalls
Rough
idle
While warming up
After warming up
While warming up
After warming up
High idle speed after
warming up
TROUBLESHOOTING PROCEDURE
Note
Step 1 under symptom is to quickly determine what system or unit may be at fault by use of the SST. (Self-Diagnosis Checker 49 H018 9A1)
1st:
Check input sensors and output solenoid valves with the
SST.
(Refer
to
page 4B—10.)

2nd:
Check other switches with the
SST.
(Refer
to
page 4B—26.)

3rd:
Check the following items:

11
Poor acceleration, hesita-
tion or lack of power
Runs rough on deceleration
Afterburn in exhaust system
Poor fuel consumption
Engine stalls or rough after hot starting
Electrical system
1) Battery condition
2) Fuses

Fuel system
1) Fuel level 2) Fuel leakage
3) Fuel filter 4) Idle speed

Engine
1) Compression 2) Overheating

Ignition system

1) Ignition spark 2) Ignition timing

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 4B—8.)

76G04B-003
4B—7

4B TROUBLESHOOTING WITH SST
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.
86U04A-011
Test connector: Green (1 pin)
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
(WPUTOft
SELECT
S*

5


o n==ru
o o o o 49 HO 18 9AI
76G04B-005
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 main relay (Refer
to page 4B—86), power supply circuit, and check
connector wiring.
7. If 88 flashes and the buzzer sounds continuously
for more than 20 seconds, replace the engine con-
trol 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 from 4B—14 to 4B—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 depressing the
brake pedal for at least 2 seconds; then recon-
nect the negative battery cable.
76G04B-134
4B—10

TROUBLESHOOTING WITH SST 4B
2. Connect the SST to the check connector.
3. Ground the test connector (Green, 1-pin) with a
jumper wire.
86U04A-015

Ignition switch:
ON

for six
seconds
4. Turn the ignition switch ON, but do not start the
engine for six seconds.
5. Start and warm up the engine, then run it at
2,500—3,000 rpm for three minutes in neutral.
6. Verify that no code numbers are displayed.
76G04B-006
76G04B-007
Note
The Digital Code Checker (49 G018 9A0) with
the Signal Adapter (49 9200 180) may be used
in place of the Self-Diagnosis Checker (49
H018 9A1).
4B-11

TROUBLESHOOTING WITH SST 4B
Code No. 08 (Air flow meter) PC: Possible Cause

Are there poor connections
in air
flow meter circuit?

NO

Is there continuity between
air
flow meter and engine control unit?
Air flow meter Control unit

Vb
(RB wire) 31

Vc
(RW wire) 2B

Vs
(RB wire) 2E

E2
(LgY wire) 2C

YES

Is resistance
of air
flow meter OK?
Resistance:
Terminal More then
20

E2
Vs
20—400 20—1,000
E2
Vc
100-300
E2
Vb
200-400

YES
NO
NO
YES

Is same Code.
No.
present after performing after-repair procedure? (Refer
to
page 4B—10)

VES

Are engine control unit terminal voltages OK? Check terminal: 2B, 2C, 2E,
31
(Refer
to
page 4B—89 and 4B—90)

YES
NO
NO

Repair
or
replace connector
PC: Open circuit
in
wiring harness from
air
flow
meter
to
engine control unit
Repair
air
flow meter
Air flow meter and circuit
OK

PC: Short circuit
in
wiring harness
PC: Engine control unit malfunction

76g04b-010
4B—15

4B TROUBLESHOOTING WITH SST
Code No. 15 (Oxygen sensor) PC: Possible Cause
Note
When Codes No.15 and 17 are present at the same time, first perform the checking proce-
dure for Code No.17. (Refer to page 4B—21.)
YES

PC: Engine control unit malfunction

76G04B-015
4B—20

SWITCH MONITOR FUNCTION 4B
SWITCH MONITOR FUNCTION
Individual switches can be monitored by the SST.
Note
The test connector must be grounded and the ignition switch ON (engine stopped).
Control unit
76G04B-022
Switch Self-Diagnosis Checker (Monitor lamp) Remarks Switch Light ON Light OFF Remarks

Clutch switch Pedal released Pedal depressed Gear:
IN

Neutral switch In gear Neutral Clutch pedal released
Idle switch Pedal depressed Pedal released
—

Brake light switch Pedal depressed Pedal released
—

A/C switch ON OFF Blower motor position:
"1"

position
Headlight switch ON OFF
—

Rear defroster switch ON OFF
—

Blower switch ON OFF Blower motor position:
"3"
or
"4"
position
Inhibitor switch D,
1, 2
and
R
range P and
N
range
—

Water thermo switch (Elec-trical fan) Terminal disconnected Terminal connected While fan
not
operating

4B-25

4B SWITCH MONITOR FUNCTION
49 H018 9A1
INSPECTION PROCEDURE
1. Warm up the engine to normal operating temper-
ature and stop it.
2. Connect the SST to the check connector (Green,
6-pin) and the negative battery terminal.
86U04A-034
76G04B-023
3. Connect a jumper wire between the test connec-
tor (Green, 1-pin) and a ground.
4. Turn the ignition switch ON. Check if monitor lamp
illuminates when each switch is made to function
as described below.
Caution
a) If any one of the switches is activated, the
monitor lamp will stay on.
b) Do not start the engine.
Note
The Digital Code Checker (49 G018 9A0) with
the Signal Adapter (49 9200180) may be used
in place of the Self-Diagnosis Checker.
Procedure
76G04B-024
4B—26

IDLE ADJUSTMENT 4B
76G04B-034
76G04B-035
Idle mixture
Automatic
Control
Function
Engine Control Unit

IDLE
ADJUSTMENT
IDLE SPEED
Preparation
1) Check the condition of the engine (plugs, leaks in
hoses, etc.).
2) Make sure all accessories are OFF.
3) Warm up the engine and run it for three minutes
at 2,500—3,000 rpm in neutral.
4) Check the initial ignition timing and adjust if
necessary.
Inspection and Adjustment
Caution
Disconnect the air bypass solenoid connec-
tor when checking and adjusting the idle
speed.
1. Check that the idle speed is within specification.
Specification:
MTX—800 +58 rpm
ATX—900 +58 rpm (P range)
2. If the idle speed is not within specification, remove
the blind cap from the throttle body and adjust it
by turning the air adjust screw.
IDLE MIXTURE
Because an automatic compensation function
for air/fuel mixture is built into the engine con-
trol unit, it is not necessary to check and adjust
the idle mixture.
86U04A-049
4B-29

INTAKE AIR SYSTEM 4B
76G04B-039
D C B E\\ I I A
p 'V > "
F G
76G04B-040
76G04B-041
1. Check that the throttle valve moves smoothly when
the throttle lever is moved from fully closed to fully
open.
2. Warm up the engine and run at idle.
3. Check the vacuum generated at each port as
shown in the following table.

~ —Condition
Port (Connected to) ——____ Idle Other
A (solenoid valve, EGR) No Yes
B (distributor, advance) No Yes
C (EGR modulator valve) No Yes
D (water thermo valve) No Yes
E (vacuum switch valve
&
charcoal canister) Yes
F (distributor, retard
& air
control valve) Yes
G (distributor, advance) Yes

4. If vacuum is not obtained as in the table, clean the
necessary port.
Dynamic Chamber
1. Visually check the dynamic chamber for damage.
2. Replace, if necessary.
Intake Manifold
1. Visually check the intake manifold for damage.
2. Replace, if necessary.
76G04B-042
4B—33

IDLE-UP SYSTEM 4B
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switch.
Possible
cause
\ Page
Symptom
Air valve
Air bypass solenoid valve Engine control unit
terminal
Possible
cause
\ Page
Symptom
Air valve
Idle-up singal Adjustment
Engine control unit
terminal
Possible
cause
\ Page
Symptom
Air valve
Idle-up singal Adjustment
1S 20
Possible
cause
\ Page
Symptom 4B—38 4B—39 4B—40 4B—89 4B—90
Engine
stalls
While warming up
1 2 3 4 5
Engine
stalls After warming up
1 2 3 4

Rough Idle
While warming up
1 2 3 4 5
Rough Idle After warming up
1 2 3 4

High idle speed after warming up
1 2 3 4 5

Runs rough on deceleration
1 2 3 4

Afterburn in exhaust system
1 2 3 4 5

Fails emission test
1 2 3 4 5

76G04B-045
4B-37