MAZDA 626 1987 Workshop Manual

TROUBLESHOOTING WITH SST 4B
TROUBLESHOOTING WITH SST
When troubles occur in the main input devices or output devices, check for the cause using the SST.
Failures of each input and output device are indicated and retrieved from the control unit as malfunc-
tion code numbers.
Note
The control unit constantly checks for malfunction of the input devices. But, the control
unit checks for malfunction of output devices only in a 3 second period after the ignition
switch is turned ON and the test connector is grounded.
4B—9

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

4B TROUBLESHOOTING WITH SST
PRINCIPLE OF CODE CYCLE
Malfunction codes are determined as shown below
1. Code cycle break
The time between malfunction code cycles is 4.0 sec (the time the light is off).
86U04A-017
ON
OFF
1 cycle Malfunction code
cycle break
4.0 sec.
76G04B-122
2. Second digit of malfunction code (ones position)
The digit in the ones position of the malfunction code represents the number of times the buzzer
is on 0.4 sec during one cycle.
ON
OFF
1 cycle Malfunction code
1 2 3
P "
u
4-
cycle break
0.4 0.4 sec. sec.
4.0 sec.
Malfunction
code: 03
76GC4B-123
3. First digit of malfunction code (tens position)
The digit in the tens position of the malfunction code represents the number of times the buzzer
is on 1.2 sec during one cycle.
It should also be noted that the light goes off for 1.6 sec. between the long and short pulses of
the buzzer.
1 cycle Malfunction code
nr 0.4
1.2 sec. sec
1 2 cycle break
1.6 4.0 sec.
h ~~—'sec. _ First digit Second digit
Malfunction
code: 22
76G04B-124
4B—12

TROUBLESHOOTING WITH SST 4B
CODE NUMBER
Malfunction display
Self-diagnosis Fail-safe Code
No. Output signal pattern subsystem Self-diagnosis Fail-safe

01
ON
OFF

Ignition pulse
No ignition signal
08
Air flow meter
Open
or
short circuit
Maintains basic sig-
nal
at
preset value
09
1 111

Water thermo sensor
Open
or
short circuit
Maintains constant command 35°C (95 °F)
10
Intake
air
thermo sensor (air flow meter) Open
or
short circuit
Maintains constant 20°C (68°F) command
12
£_IUILJIIL

Throttle sensor
Open
or
short circuit
Maintains constant
command
of
throttle
valve fully open
14
OFF
TL
I I nil

Atmospheric pres-
sure sensor Open
or
short circuit
Maintains constant command
of
sea level pressure
15
oTp m 11 [U

Oxygen sensor Sensor output con-tinues less than 0.55V 120 sec. after engine starts (1,500 rpm)
Cancels EG
I
feed-
back operation
17
SLJlMJl

Feedback system Sensor output
not
changed
20
sec.
af-
ter engine exceeds 1,500 rpm
Cancels EGI feed-back operation
25
^JMLJl

Solenoid valve (pres-
sure regulator)
Open
or
short circuit
26
SUUBUIL

Solenoid valve (purge control)
Open
or
short circuit 28
£ mi in nr

Solenoid valve
(EGR) Open
or
short circuit
34
^jmiUTT

Air bypass solenoid
valve (Idle-up
C)

Open
or
short circuit
35
0Nnnnj OFFU u UUU
"fin nnr
Air bypass solenoid
valve (Idle-up
B)

Open
or
short circuit

76G04B-008
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 2 seconds to erase the memory of a mal-
function code.
4B-13

4B TROUBLESHOOTING WITH SST
If a malfunction code number is shown on the SST, check the following chart along with the wiring
diagram.
Code No. 01 (Ignition pulse) PC: Possible Cause
76G04B-009
4B—14

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. 09 (Water thermo sensor) PC: Possible Cause

Are there poor connections
at
water thermo sensor circuit?

NO
YES
Repair
or
replace connector
Is there continuity between water thermo sensor and control unit?
Water thermo sensor Control unit
A (YB wire) 21
B (LgY wire) 2C

YES

Is resistance
of
the water thermo sensor OK? Resistance:
Coolant temp Resistance
-20°C
(
-4°F) 14.5-17.8 k£2
20°C
(
68°F) 2.2- 2.7
kQ

40°C (104°F) 1.0- 1.3
kfi

60°C (140°F) 500—640
Q

80°C (176°F) 280-350
Q
NO
PC: Open circuit
in
wiring harness from water thermo sensor
to
engine control unit

NO
Replace water thermo sensor

| YES

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

YES

Are engine control unit
21
OK? (Refer
to
page 4B—8
and
2C
terminal voltages
3)

NO
Water thermo sensor and circuit
OK
NO
PC: Engine short circuit
in
wiring harness

YES

PC: Engine control unit malfunction

76G04B-011
4B—16

TROUBLESHOOTING WITH SST 4B
Code No. 10 (Intake air thermo sensor) PC: Possible Cause

Are there poor connections
in air
flow meter circuit?

NO

Is there continuity between intake
air
thermo sensor (in
air
flow meter) and engine control unit?

YES

Intake
air
thermo sensor
(in
air
flow meter) Control unit
THA
(R
wire) 2J

E2
(LgY wire) 2C

NO

Repair
or
replace connector
PC: Open circuit
in
wiring harness from intake air thermo
sensor (in air flow meter)
to
engine control unit

YES

Is resistance
of
intake
air
thermo sensor (in
air
flow meter) OK?
Resistance:
Terminal Resistance
E2 <- THA -20°C
(
—4°F)
:
13.6-18.4
kfl
20°C
(
68°F)
:
2.21— 2.69
kfl
60°C (140°F)
:
493— 667
fl
NO
YES

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

YES

Are engine control unit
2J
and
2C
terminal voltages OK? (Refer
to
page 4B—89)

YES
NO
NO

Replace
air
flow meter
Intake
air
thermo sensor and circuit
OK

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

76G04B-012
4B—17

4B TROUBLESHOOTING WITH SST
Code No. 12 (Throttle sensor) PC: Possible cause
76G04B-013
4B—18