Isuzu 1999 RODEO Workshop Manual page 1649

6E2–406
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
f Restricted air intake system – Check for a possible
collapsed air intake duct, restricted air filter element,
or foreign objects blocking the air intake system.
f Throttle body – Check for objects blocking the IAC
passage or throttle bore, excessive deposits in the IAC
passage and on the IAC pintle, and excessive deposits
in the throttle bore and on the throttle plate.
f Large vacuum leak – Check for a condition that causes
a large vacuum leak, such as an incorrectly installed or
Step
1 Was the "On-Board Diagnostic (OBD) System Check"
performed?
2 1. Start the engine.
2. Turn all accessories "OFF"(A/C, rear defroster,
etc).
3. Using a Tech 2, command RPM up to 1500, down to
500, and then up to 1500 while monitoring the
"Engine Speed" on the Tech 2.
NOTE: This Tech 2 command may cause the engine to
"cut out" when RPM goes above 1500. If this occurs,
the "cutting out" will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.
Does the "Engine Speed" remain within the specified
value of the "Desired Idle" for each RPM command?
3 1. Disconnect the IAC.
2. Install IAC Noid Light J 37027 or equivalent.
3. With the engine running, command RPM up to
1500, down to 500, and then up to 1500 while
observing the noid light.
NOTE: This Tech 2 command may cause the engine to
"cut out" when RPM goes above 1500. If this occurs,
the "cutting out" will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.
Does each noid light cycle red and green (never
"OFF")?
4 1. Check the following circuits for an open, short to
voltage, short ground, or poor connections at the
PCM:
f
IAC "A" Low.
f
IAC "A" High.
f
IAC "B" Low.
f
IAC "B" High.
2. If a problem is found, repair as necessary,
Was a problem found?
DTC P1508 –IAC System Low RPM
Action
faulty PCV valve or a disconnected brake booster
hose.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
Value(s)
— Go to Step 2
No trouble
found. Go to
Diagnostic
50 RPM
— Go to Step 5
— Verify repair
Yes No
Go to OBD
System
Check
Go to Step 3
Aids
Go to Step 4
Go to Step 8