Possible causes – IACV-AAC valve harness is open or shorted– IACV-AAC valve poor electrical connection– Faulty IACV-AAC valve When is the obd code mean? The P0505 code is set when the IACV-AAC valve does not operate properly. Symptoms – Engine Light ON (or Service Engine Soon Warning Light)– Engine hard to start– Rough or erratic…