SERVICE MANUAL NUMBER 23
GENERAL SYSTEM DIAGNOSTICS
Chart A-8 (2 of 2): Idle Air Control (IAC) Functional Test
Step
Action
Value(s)
Yes
No
Was the “On-Board Diagnostic”
1
(OBD)
performed?
System
Check
–
Go to OBD
Go to Step 2 System Check
1.
Engine should be at normal
operating temperature.
Start engine and allow idle to
stabilize.
2.
3.
4.
Record RPM.
Ignition
“OFF”
for
10
seconds.
Disconnect IAC harness con-
nector.
Restart engine and record
RPM.
2
200 RPM
5.
6.
Is RPM Higher Than The First
Recorded RPM By More Than
The Specified Value?
Go to Step 3
Go to Step 4
1.
Reinstall IAC harness con-
nector.
2.
Idle speed should gradually
return within 75 RPM of the
original recorded RPM within
3
–
30
seconds.
Does RPM Return To Original
Recorded RPM?
Go to Step 5
Go to Step 4
1.
2.
3.
Ignition
seconds.
Disconnect IAC harness con-
nector.
Restart engine.
“OFF”
for
10
4
4. Using a test light connected
to ground, probe each one of
the four IAC harness termi-
nals.
–
Does The Test Light Blink On
All Four Terminals?
Go to Step 7
–
Go to Step 6
–
5
6
IAC circuit is functioning properly.
–
–
Locate
and
repair
poor
connection, open, or short to
ground in the IAC circuit that did
not blink. If a problem was found,
repair as necessary.
Go to OBD
System
Check
Was A Problem Found?
Go to Step 8
–
Check for poor IAC connections
or replace the faulty IAC valve.
Go to OBD
System
Check
7
8
–
–
Is Action Complete?
Repair faulty ECM connections
or replace faulty ECM.
Is Action Complete?
Go to OBD
System
Check
–
Index
90-861326--1
MARCH 1999
Page 5E-91
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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