My wife's '98 Outback has suddenly decided to thow a code. It is code P0507, saying that the idle control system RPM is higher than expected.

 

It has never done this before. I reset it and the car is running fine right now. What are the ususal suspects for this code? A sensor issue?

 

David Nolen

The Subaru diagnostics section 1st asks "were there any other codes?" Since you didn't specify, I'll guess not. Then it states 2 or more driving cycles with the idle at a higher RPM then the ECU specified. Check for:

 

Air leaking into the intake manifold at the throttle body, any loose components, hoses all connected and not cracked. In short any intake leaks. No Faults found there, then:

 

Ensure the throttle cable has enough play allowing the throttle plate to close and the Idle Air Solenoid to do it's job at the ECU request. No fault found there, then:

 

Remove the Idle Air Solenoid and inspect it for any foreign particles which may hold the passages open. No Fault found there, then:

Replace the Idle Air Solenoid.

Thanks for the info. There were no other codes and after reset, the problem went away (for the time being). As we all know, it will be back!