Idle Air Control System RPM Too High
2006-2011 Buick Lucerne 3.9L V6
Description
The PCM detected that the engine idle speed is higher than the specified maximum range and the IAC system is not responding to correct it.
Symptoms
- High idle speed
- Engine revving at idle
- Difficulty slowing engine
- Revving when coming to a stop
- Erratic idle speed
Common Causes
- Faulty IAC valve stuck open
- Vacuum leak
- Dirty throttle body with air bypass
- Faulty IAC valve wiring
- PCM failure (rare)
- Intake manifold gasket leak
Diagnostic Steps
- Unplug IAC connector and check if idle normalizes
- Check for vacuum leaks
- Inspect throttle body for air bypass around blade
- Test IAC valve operation with scan tool
- Check intake manifold gaskets
Repair Notes
Check for vacuum leaks first. Clean throttle body. Replace IAC valve if stuck open.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0011Intake Camshaft Position Timing Over-Advanced Bank 1
- P0012Intake Camshaft Position Timing Over-Retarded Bank 1
- P0013Exhaust Camshaft Position Actuator Circuit/Open Bank 1
- P0014Exhaust Camshaft Position Timing Over-Advanced Bank 1
- P0015Exhaust Camshaft Position Timing Over-Retarded Bank 1
P1509 on Other Vehicles
Common Questions
What does code P1509 mean on a 2006-2011 Buick Lucerne?
P1509 stands for "Idle Air Control System RPM Too High". The PCM detected that the engine idle speed is higher than the specified maximum range and the IAC system is not responding to correct it.
What are the symptoms of P1509 on a Buick Lucerne?
Common symptoms of P1509 include: High idle speed, Engine revving at idle, Difficulty slowing engine, Revving when coming to a stop, Erratic idle speed.
What causes P1509 on a 2006-2011 Buick Lucerne?
Common causes of P1509 include: Faulty IAC valve stuck open, Vacuum leak, Dirty throttle body with air bypass, Faulty IAC valve wiring, PCM failure (rare), Intake manifold gasket leak.