Possible causes

– Idle Air Control Valve harness is open or shorted
– Idle Air Control Valve circuit poor electrical connection
– Faulty Idle Air Control Valve

When is the code detected?

Powertrain Control Module (PCM) has detected an electrical load failure on the IAC circuit.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1504 FORD Description

The Idle Air Control Valve (IACV) is used to control engine idle speed and allows air to bypass the throttle plate. The amount of air allowed to bypass is determined by the Powertrain Control Module (PCM) and controlled by a duty-cycle signal.

FORD Technical Service Bulletins for P1504 code