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Diagnostic Procedure

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P0508-IAC VALVE SIGNAL CIRCUIT LOW DIAGNOSTIC TEST REFERENCE

TEST ACTION APPLICABILITY
1
NOTE: If the engine will not idle, maintain an engine speed between 800 and 1500 RPM.
Start the engine.Allow the engine to idle.Check for vacuum leaks, proper PCV valve installation, proper MAP Sensor installation, and proper IAC installation.With the DRBIII®, read the IAC Current.Is the IAC Current below 146 mA?Yes --> Go To 2No --> Refer to the INTERMITTENT CONDITION SYMPTOM .Perform POWERTRAIN VERIFICATION TEST VER - 5 .		 All
2 Turn the ignition off.
Disconnect the IAC Motor harness connector.
Remove the IAC Motor.
NOTE: Inspect the IAC air passages for restriction and damage to the IAC valve.

Measure the resistance across the IAC Motor pin terminals (component).
Is the resistance 9.7 +/- 1.0 ohms?
Yes --> Go To 3
No --> Replace the IAC Motor.
Perform POWERTRAIN VERIFICATION TEST VER - 5 .		 All
3 Disconnect the C2 PCM harness connector.
CAUTION: DO NOT PROBE THE PCM HARNESS CONNECTORS. PROBING THE PCM HARNESS CONNECTORS WILL DAMAGE THE PCM TERMINALS RESULTING IN POOR TERMINAL TO PIN CONNECTION. INSTALL MILLER SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.

Measure the resistance of the (K961) IAC Signal circuit from the IAC Motor harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
Yes --> Go To 4
No --> Repair the open in the (K961) IAC Signal circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 5 .		 All
4 Measure the resistance between ground and the (K961) IAC Signal circuit in the IAC Motor harness connector.
Is the resistance below 100 ohms?
Yes --> Repair the short to ground in the (K961) IAC Signal circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 5 .
No --> Go To 5		 All
5
CAUTION: DO NOT PROBE THE PCM HARNESS CONNECTORS. PROBING THE PCM HARNESS CONNECTORS WILL DAMAGE THE PCM TERMINALS RESULTING IN POOR TERMINAL TO PIN CONNECTION. INSTALL MILLER SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.
Measure the resistance of the (K61) IAC Control circuit from the IAC Motor harness connector to the appropriate terminal of special tool #8815.Is the resistance below 5.0 ohms?Yes --> Go To 6No --> Repair the open in the (K61) IAC Control circuit.Perform POWERTRAIN VERIFICATION TEST VER - 5 .		 All
6 Measure the resistance between ground and the (K61) IAC Control circuit in the IAC Motor harness connector.
Is the resistance below 100 ohms?
Yes --> Repair the short to ground in the (K61) IAC Control circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 5 .
No --> Go To 7		 All
7
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.If there are no possible causes remaining, view repair.RepairReplace and program the Powertrain Control Module per Service Information.Perform POWERTRAIN VERIFICATION TEST VER - 5 .		 All
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