Low Idle Speed - Mazda MX-5 1990 Workshop Manual

F
TROUBLESHOOTING GUIDE
12 LOW IDLE SPEED - WHEN AIC, PIS, OR ElL ON
DESCRlp· • Engine speed decreases at idle when AIC, PIS, or ElL ON
TION • AIC, PIS, headlights, blower fan and electric cooling fan operate normally
[TROUBLESHOOTING HINTS]
CD
Idle speed control malfunction • ISC valve stuck
• Engine speed feedback control malfunction
STEP
INSPECTION ACTION
Check if "00" is displayed on Self-Diagnosis
Checker with ignition switch ON
c:::::r page F-78
Yes Go to next step
No
Malfunction Code No. displayed
Check for cause (Refer to specified
check sequence)
"66" flashes
Check ECU terminal 1 F voltage
VOltage: Approx. 12V
(Ignition switch ON)
c:::::r page F-80
c:r
page F-128
¢
If OK, replace ECU
L7
page F-127
2
3
4
F-38
Check switches for correct operation with Self-
Diagnosis Checker Monitor Lamp and ignition
switch ON
L7
page
F-89
~="",,-~SYSTEM
SELECT 1
TEST SW
SELF TEST
Check if continuity exists between diagnosis con-
nector termin~N and ground~
o -
) ISEPB3
-
~.)
)~
(
\
Disonnect ISC valve connector at idle and check
if "clicking" is heard from ISC valve
Yes
No
Yes
No
Yes
¢
If not OK, check wiring between
ECU and Self-Diagnosis Checker
c:::J
page F-7
Go to next step
Lamp not ON/OFF with specified
switch
Check for cause (Refer to specified
check sequence)
Lamp always ON
Check wiring between ECU terminal 1 D
LI
page
F-90
and Self-Diagnosis Checker
c:::::r
page F-7
Check for short circuit in wiring be-
tween diagnosis connector terminal
TEN and ground
c:r
page F-7
Go to next step
Try known good ECU
LI
page F-127
No Replace ISC valve
c:::::r
page F-99
05UOFX·029