P1504 Idle air control circuit malfunction. where do I start?

Question

I dont know where to start looking

Answer 1

P1504 IAC air control

Start by looking for vacuum leaks that causes false air. , Vacuum leaks are air leaks that gets past the MAF (mass air flow) that is unmetered, this includes the MAF airflow duct, the PCV valve and hose for any rupture , If there is no vacuum leaks , the IAC posrt needs to be inspected for blockage or plugging you will also need to  test the the IAC start by it resistance the OHMS of the IAC should be 6.0 to 13.0 OHMS.