P1507moderate severityPowertrain
Idle Control System Malfunction Fail Safe
on 2004 Subaru Legacy 3.0L H6 · AWD
What this code means
The PCM has entered failsafe mode for the idle control system. The idle speed control cannot maintain target idle and has exceeded the correction range, triggering a failsafe idle speed that may be higher or lower than normal.
Symptoms
- Check Engine Light
- Idle speed fixed at failsafe value
- Rough or unstable idle
- Engine may stall
- Poor idle quality
Common causes
- Large vacuum leak
- Faulty idle air control valve
- Dirty throttle body restricting airflow
- Carbon buildup in IAC passages
- Intake manifold gasket leak
Diagnostic steps
- Perform smoke test for vacuum leaks
- Clean throttle body and IAC passages
- Test IAC valve operation
- Check intake manifold gaskets
- Monitor IAC duty cycle on scan tool
Repair notes
Locate and repair vacuum leaks; clean the throttle body and IAC system.
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