Check Point For Each Terminal - Mazda MX-5 1990 Workshop Manual

CONTROL SYSTEM·
F
Check Point for Each Terminal
Terminal Connection to
Abnormal voltage Possible cause
1A Battery Always approx. OV • ROOM 10A fuse burned
(Battery OK) • Open circuit in wiring from ROOM 10A fuse to ECU
terminal 1A
1B
Main relay Always approx. OV
• Main relay malfunction (Refer to page F-139)
• Open circuit in wiring from main relay to ECU
terminal 1 B
1C
Ignition switch Always approx. OV
• Open circuit in wiring from starter interlock switch to
(Start position)
(Starter turns) ECU terminal 1 C
10 Self-Diagnosis
Always approx. OV • Main relay malfunction (Refer to page F-139)
Checker (Monitor lamp)
• Open circuit in wiring from main relay to diagnosis
connector terminal
+
B
• Open or short circuit in wiring from diagnosis
connector terminal MEN to ECU terminal 10
Always approx. 12V • Poor connection at ECU connector
• ECU malfunction
Always approx. 5V
• ECU malfunction
1E Malfunction indicator
Always tlOW 2.5V
• Short circuit in wiring from combination meter to
lamp (MIL) (MIL alw ys ON) ECU terminal 1 E
• ECU malfunction
Always below 2.5V • Open circuit in wiring from combination meter to
(MIL never ON) ECU terminal 1 E
Always approx. 12V
• Poor connection at ECU connector
• ECU malfunction
1F Self-Diagnosis Checker Always below 2.5V • Main relay malfunction (Refer to page F-139)
(Code No.) (No display on Self-Diagnosis • Open circuit in wiring from main relay to diagnosis
Checker) connector terminal + B
Always below 2.5V • Open or short circuit in wiring from diagnosis
("88" is displayed and connector terminal FEN to ECU terminal 1 F
buzzer sounds continuously)
Always approx. 12V • Poor connection at ECU connector
• ECU malfunction
1G Igniter Always approx. OV Refer to Code No.01 troubleshooting
1H (Refer to page F-81)
1J A/C relay Always below 2.5V • AIC relay malfunction (Refer to page U-39)
(A/C does not operate) • Open circuit in wiring from main relay to A/C relay
• Open circuit in wiring from
A/C
relay to ECU termi-
nal 1J
Always below 2.5V
• Short circuit in wiring from
A/C
relay to ECU terminal
(A/C
switch OFF but
A/C
1J
operates)
• ECU malfuction
Always approx. 12V • A/C switch malfunction (Refer to page U-25)
• Poor connection at ECU connector
• ECU malfunction
1K Diagnosis connector Always approx. OV • Short circuit in wiring from ECU terminal 1 K to diag-
(T erminal TEN) nosis connector terminal TEN
Always approx. 12V • Open circuit in wiring from ECU terminal 1 K to diag-
nosis connector terminal TEN
• Open circuit in wiring from diagnosis connector ter-
minal GND to ground
iN Throttle sensor
Always approx. OV • Throttle sensor misadjustment (Refer to page F-136)
(Idle terminal) • Short circuit in wiring from ECU terminal 1 N to throt-
tle sensor
• ECU malfunction
Always approx. 12V • Throttle sensor misadjustment (Refer to page F-136)
• Open circuit in wiring from ECU terminal 1 N to throt-
tle sensor
• Open circuit in wiring from throttle sensor to ground
10 Stoplight switch Always approx. OV
• Open cir.cuit in wiring from stoplight switch to ECU
(Stoplights OK) terminal 10
F-131