Suzuki Engine 2002 GRAND VITARA SQ420 Service Manual page 268

SYSTEM DESCRIPTION
Refer to "Air Intake System Description" in Section 6E2.
DTC DETECTING CONDITION AND TROUBLE AREA
DTC DETECTING CONDITION
Idle engine speed is lower than desired engine speed
100 r/min. though IAC valve opening is about 100%.
Idle engine speed is higher than desired engine speed
200 r/min. though IAC valve opening is about 0%.
IAC valve monitor voltage is high.
DTC CONFIRMATION PROCEDURE
NOTE:
Check to make sure that following conditions are satisfied when using this DTC CONFIRMATION PRO-
CEDURE.
• Intake air temperature : between –14°C and 70°C (6.8°F and 158°F)
• Atmospheric pressure : higher than 560 mmHg (Altitude : lower than 2790 m (9150 ft))
1) With ignition switch OFF, connect scan tool.
2) Turn ON ignition switch and clear DTC by using scan tool if any.
3) Start engine and warm up to normal operating temperature.
4) Run engine at idle speed for 30 sec.
5) Check DTC and pending DTC by using scan tool.
DTC TROUBLESHOOTING
Step
1 Was "Engine Diag. Flow Table" performed?
2 Idle Speed check :
1) Check idle speed and idle air control duty
referring to "Idle Speed/Idle Air Control
(IAC) Duty Inspection" in Section 6E2.
Are they in good condition?
3 IAC Valve inspection :
1) Inspect IAC valve referring to "Idle Air Con-
trol Valve (IAC valve)" in Section 6E2.
Is it in good condition?
4 IAC Valve Circuit check :
1) With ignition switch OFF, disconnect ECM
(PCM) couplers.
2) Check resistance between C51-2-14 and
C51-2-15, C51-2-24 and C51-2-25.
Is each resistance 40 – 48
ENGINE GENERAL INFORMATION AND DIAGNOSIS (H25 ENGINE) 6-1-127
Action
Ω
?
TROUBLE AREA
IAC valve or its circuit
Air intake system
VSS
Engine mechanical
External load
ECM (PCM)
Yes
Go to Step 2.
Intermittent trouble.
If OK, substitute a known-
good ECM (PCM) and
recheck.
Go to Step 6.
Go to Step 5.
No
Go to "Engine Diag. Flow
Table".
Go to Step 3.
Go to Step 4.
Faulty "LT GRN/BLK",
"PPL/BLK", "GRY/BLU" or
"PPL/YEL" wire.
If OK, faulty IAC valve.