Suzuki Liana RH418, Supplementary Service Manual

Page: 103 / 371

Engine General Information and Diagnosis: 1A-90
Troubleshooting
Step Action Yes No
1 Engine idle speed and IAC duty check
1) Check idle speed / idle air control duty referring to “Idle
Speed / Idle Air Control (IAC) Duty Inspection”.
Is idle speed within specification?
Go to Step 2. Go to Step 4.
2 Is IAC duty within specification in Step 1? Go to Step 3. Check for the
followings: Vacuum
leak, EVAP canister
purge control system,
Clog of IAC air passage,
Accessory engine load,
Closed throttle position
(TP sensor), Stuck of
PCV valve.
3 Is engine idle speed kept specified speed even with
headlight ON? If vehicle with power
steering system, go to
Step 4.
If vehicle without power
steering system, system
is in good condition. Check electric load
signal circuit referring to
“Electric Load Signal
Circuit Check”.
If check result is OK,
check IAC system for
operation referring to
Step 2 or Step 3 of “Idle
Air Control Circuit
Check”.
4 Is engine idle speed kept specified speed even with steering
wheel turned to the right or left as far as it stops (vehicle with
power steering system)? System is in good
condition. Check power steering
pressure switch signal
circuit referring to
“Power Steering
Pressure (PSP) Switch
Signal Circuit Check”.
If check result is OK, go
to Step 5.
5 Was idle speed higher than specification in Step 1? Go to Step 6. Go to Step 9.
6 1) Check A/C (input) signal circuit referring to Step 2 of “A/
C Control System Check (Vehicle with A/C)”, if
equipped. (A/C signal can be also checked by using
SUZUKI scan tool.)
Is it in good condition?
Go to Step 7. Repair or replace A/C
signal circuit or A/C
system.
7 1) Check IAC system referring to Step 2 or Step 3 of “Idle
Air Control Circuit Check”.
Is check result satisfactory?
Go to Step 8. Go to Step 5 of “Idle Air
Control Circuit Check”.
8 Was IAC duty less than about 3% (or more than about 97%)
for OFF duty meter in Step 1? Check abnormal air
inhaling from air intake
system, PCV valve and
EVAP canister purge
control system. Check TP sensor
(closed throttle position)
and ECT sensor for
performance.
If sensors are OK,
substitute a known-
good ECM.
9 Is SUZUKI scan tool available? Go to Step 10. Go to Step 11.