Applicable Systems
OBD-II
Symptoms
Engine idle RPM above target; IAC valve or throttle body allowing too much air at idle; high idle.
Possible Causes
- IAC valve stuck open
- Vacuum leak (unmetered air)
- Throttle body not closing fully (carbon buildup)
Troubleshooting Steps
- Step 1: Check IAC valve operation
IAC responds - Step 2: Check for vacuum leaks
No leaks - Step 3: Inspect throttle body for carbon preventing full close
Throttle body clean - Step 4: Clean throttle body and IAC
Throttle plate closes fully - Step 5: Clear code and perform idle relearn
Idle at target RPM
How to Reset
Clear with OBD-II scanner; requires idle relearn.
Common Replacement Parts
- Throttle Body Cleaner
- IAC Valve (if needed)
Frequently Asked Questions
- Q: Common cause of high idle?
Vacuum leak or dirty throttle body. Check PCV valve, intake gaskets, and vacuum hoses. Clean throttle body before replacing IAC.
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Source: SAE J2012 standard DTC list + OBD-II portal
Category: OBD-II
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