Possible causes

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

Symptoms

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

P1504 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.

P1504 Information for specific makes

P1504 BUICK
P1504 CADILLAC
P1504 CHEVROLET
P1504 FORD
P1504 GMC
P1504 HYUNDAI