-- IAC circuit short to GND.
-- IAC valve assembly stuck open.
-- Vacuum leak.
-- Damaged IAC valve assembly.
-- Damaged throttle body.
-- Damaged PCM.
Key on, engine running.
With the engine at idle, listen for vacuum leaks.
Inspect the entire intake air system from the Mass Air Flow (MAF) sensor to the intake manifold for damage or leaks such as:
Cracked or punctured intake air tube.
Loose intake air tube at the air cleaner housing or throttle body.
IAC valve assembly or gasket seal.
Intake manifold assembly or gasket seal.
EGR valve gasket seal.
Vacuum supply connectors and hose.
PCV valve, connectors and hose.
Are any leaks detected in the above areas?
KE21 CHECK EVAP SYSTEM FOR A STUCK OPEN VALVE
Disconnect hoses at EVAP Canister Purge Valve.
Connect a hand vacuum pump to the fuel vapor port to EVAP canister at the EVAP Canister Purge Valve.
Apply 53 kPa (16 in-Hg) of vacuum to EVAP Canister Purge Valve.
Does the EVAP Canister Purge Valve hold vacuum for 20 seconds?