P1504moderate severityPowertrain
Idle Air Control Circuit Malfunction
on 2004 Lincoln Aviator 4.6L V8 DOHC · AWD
What this code means
The Idle Air Control (IAC) valve circuit has a malfunction. The IAC valve controls engine idle speed by regulating the amount of air bypassing the throttle plate.
Symptoms
- Check Engine Light
- Erratic idle speed
- Idle too high or too low
- Engine stalling at idle
- Rough idle
Common causes
- Faulty IAC valve
- Carbon buildup on IAC valve or throttle body
- Wiring issue to IAC
- Vacuum leak affecting idle
- Dirty throttle body
Diagnostic steps
- Test IAC valve resistance
- Clean IAC valve and throttle body
- Inspect IAC wiring and connector
- Check for vacuum leaks
- Monitor IAC duty cycle on scan tool (should be 22-65%)
Repair notes
Clean throttle body and IAC valve first. Replace IAC if faulty. Repair vacuum leaks.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1