P1551,P1552, P1553
Symptom: Low, high or hunting idle speed. Idle speed sensitive to load changes.
Idle air control (IAC) valve
Fault symptoms
Low, high or hunting idle speed. Idle speed sensitive to load changes.
Conditions
P1551 Open circuit.
P1552 Short circuit to battery positive (B+).
P1553 Short circuit to ground.
Check the wiring
Intermittent faults may occur as a result of temporary short circuits and breaks in the
wiring. Jiggle the wiring at several points and in different directions to ascertain whether the
wiring harness, including any connectors, is causing the trouble. Observe the multimeter,
ISAT scan tool or test lamp while doing this.
Diagnostic procedure
1. Check the idle air control valve's power supply
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Unplug the valve's
connector.
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Connect the test lamp to the connector between:
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Turn the ignition switch to the ON
position.
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The test lamp should light up.
Did the test lamp light up?
Continue with point 2.
Repair or replace the lead between the 3-pin connector and crimped
connection J31. Continue with point 3.
2. Check the control module's outputs to the idle air
control valve
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Connect the test lamp
to:
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Connect the ISAT Scan Tool.
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Turn the ignition switch to the ON position.
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The test lamp should flash at a frequency of 0.5 Hz for 30
seconds.
Test lamp flashing?
Change the idle air control valve. Continue with point 3.
Repair or replace the appropriate lead. Continue with point 3.
3. Final check
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Clear the diagnostic trouble code.
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Implementation of driving cycle:
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Evaluation of driving cycle:
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Has the diagnostic trouble code recurred?
Continue as described in
.
The steps taken to rectify the fault were correct.
