1987 MAZDA 626 Workshop Manual

4C TROUBLESHOOTING WITH SST
Code No.2 (Ne signal) PC: Possible Cause
YES
PC: Engine control unit malfunction
76G04C-019
Code No.3 (G signal) PC: Possible Cause
4C-16

TROUBLESHOOTING WITH SST 4C
76G04C-020
Code No.05 (Knock sensor) PC: Possible Cause
76G04C-021
Code No.08 (Air flow sensor) PC: Possible Cause
Next page
4C—17

4C TROUBLESHOOTING WITH SST
Is there continuity between air flow sensor and
engine control unit?
Air flow sensor Engine control unit
D (RB wire) 2E
E (RW wire) 2B
NO
YES
Is there 12V at terminal B of air flow sensor connector? (Refer to page 4C—103)
YES
Is there continuity between terminal F of air flow sensor and ground? (Refer to page 4C-103)
YES
NO
NO
PC: Open circuit in wiring harness
PC: Open or short circuit in wiring harness from terminal B to control relay
PC: Open circuit in wiring harness
PC: • Engine control unit malfunction • Short circuit in wiring from terminal D of air flow sensor to engine control unit
76G04C-022
Code No. 09 (Water thermo sensor)
Are there poor connections in water thermo sensor circuit?
NO
Is there continuity between water thermo sensor and engine control unit?
YES
Is resistance of the water thermo sensor OK? Resistance:
YES
Water thermo sensor Enaine control unit
A (YB wire) 21
B (LgY wire) 2C
NO
Coolant temp Resistance
-20°C ( —4°F) 14.5-17.8 kfl
20°C ( 68°F) 2.2- 2.7 kfi
40°C {104°F) 1.0- 1.3 kfi
60°C (140°F) 500-640 fi
80°C (176°F) 280-350 fi
NO
YES
Is same Code No. present after performing after-repair procedure? (Refer to page 4C—12)
YES
Are engine control unit 21 and 2C terminal voltages OK? (Refer to page 4C—98)
YES
NO
NO
PC: Possible Cause
Repair or replace connector
PC: Open circuit in wiring harness from water thermo sensor to engine control unit
Replace water thermo sensor
Water thermo sensor and circuit OK
PC: Short circuit in wiring harness
PC: Engine control unit malfunction
76G04C-023
4C—18

TROUBLESHOOTING WITH SST 4C
No. 11 Code (Intake air thermo sensor) PC: Possible Cause
NO
Is there continuity between intake air thermo sensor
(dynamic chamber) and engine control unit?
Intake air thermo sensor (dynamic chamber) Engine control unit
A (RC wire) 2J
B (LgY wire) 2C
YES
Is resistance of intake air thermo sensor (dynamic chamber) OK? Resistance:
NO PC: Open circuit in wiring harness
Temperature Resistance
20°C (68°F) 29.7-36.3 kQ
50°C (122°F) 8.4-10.2 kQ
85°C (185°F) 2.5-3.1 kQ
NO Replace intake air thermo sensor (dynamic chamber)
YES
76G04C-024
Code No. 12 (Throttle sensor) PC: Possible cause
Next step
4C-19

4C TROUBLESHOOTING WITH SST
76G04C-025
Code No. 15 (Oxygen sensor) PC: Possible Cause
76G04C-026
4C—20

TROUBLESHOOTING WITH SST 4C
Code No. 17 (Feedback system) PC: Possible Cause
Feedback system OK
76G04C-027
Code No. 25 (Solenoid valve-Pressure regulator control (PRC)) PC: Possible Cause
Repair or replace connector
Replace solenoid valve
76G04C-028
Warm up engine and run at 2,500—3,000 rpm for
three minutes Is Code No. still present?
Yes
Are there poor connections in solenoid valve circuit?
NO
Is there continuity of solenc )id valve?
YES
4C—21

4C TROUBLESHOOTING WITH SST
Code No. 26 (Solenoid valve—No. 1 purge control) PC: Possible Cause
YES
YES
Is there continuity between solenoid valve and engine control unit?
Solenoid valve Engine control unit
WG wire 2P
NO PC: Open circuit in wiring harness from solenoid valve to engine control unit
YES PC: • Engine control unit malfunction • Short circuit in wiring harness
76G04C-029
Code No. 27 (Solenoid valve—No. 2 purge control) PC: Possible Cause
Are there poor connections in solenoid valve circuit? YES Repair or replace connector
NO
NO Is there continuity of solenoid valve? NO Replace solenoid valve
YES
Is there battery voltage at RB wire of solenoid valve connector?
NO PC: Open circuit in wiring harness from RB wire to
control relay (for engine control unit)
YES
Is there continuity between solenoid valve and en-
gine control unit?
Solenoid valve Enaine control unit
WB wire 20
NO PC: Open circuit in wiring harness from solenoid valve to engine control unit
YES PC: • Engine control unit malfunction • Short circuit in wiring harness
76G04C-030
4C—22

TROUBLESHOOTING WITH SST 4C
Code No. 28 (Solenoid valve—EGR) PC: Possible Cause
Are there poor connections in solenoid valve circuit? YbS Repair or replace connector
NO
NO Is there continuity of solenoid valve? NO Replace solenoid valve
YES
Is there battery voltage of RB wire of solenoid valve connector?
NO PC: Open circuit in wiring harness from RB wire to control relay (for engine control unit)
YES
Is there continuity between solenoid valve and en-gine control unit?
Solenoid valve Engine control unit
WL wire 2N
NO^ PC: Open circuit in wiring harness from solenoid valve to engine control unit
YES PC: • Engine control unit malfunction • Short circuit in wiring harness
76G04C-031
Code No. 34 (Solenoid valve—Idle speed control (ISC)) PC: Possible Cause
YES PC: • Engine control unit malfunction • Short circuit in wiring harness
76G04C-032
4C-23