P0505 obd2 code and how to check your idle speed control valve circuits

Checking P0505 code requires checking the idle control valve circuits and its wirings. Browse also our check engine codes list below so you will know the description of the obd2 codes

P0505 Engine Idle Air Control Fault

This code can be tested by using some basic test like testing for vacuum leaks to see if it is the source of erratic idle speed control valve malfunction. Take note that your iac control motor is the device that stabilizes your engine idle speed and if you have a vacuum leak, the iac motor will try to compensate for the leak.

If you recall, vacuum leak will cause your engine rpm to rev up and it is the job of the iac motor to bring it down after being monitored by the ecm. However, if there is no leak, it is obviuos it is not a vacuum related problem but the iac motor itself. To test, disconnect the iac wiring connections and see if there is a change on the idle rpm. If not, replace the iac motor but do forget to follow the code resetting so the iac motor speed can go to the "relearn mode ".

Servicing the idle speed control valve:

When servicing the idle speed control valve, remove any carbon soot and make sure the cone seal area is clean and in good condition by using a bit of fine steel wool on the cone. The carburetor cleaner can be sprayed into the port and a large Phillips head screwdriver wrapped in a rag to clean and remove a good amount of carbon soot from the port. To measure the pintle on the new IAC valve, make sure it is longer than 1 in. The common strategy is to open the idle air-bypass valve electrically to let some more air in for better cleaning.

Before reinstalling the idle control valve, measure the distance that the IAC valve is extended from the motor housing to the end of the IAC cone. It should not exceed "1-1/8"(or contact ATS for proper specs for different engines) or damage to the IAC valve may occur when installed again.

iac motor

This servicing assumes that the IAC motor has been checked for proper electrical resistance. (Shown in the picture on the left above is an IAC valve for FORD engine).

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