P1509 CADILLAC – Idle Speed High Idle Air Control System Not Responding

P1509 CADILLAC Possible Symptoms

Engine Light ON (or Service Engine Soon Warning Light),Engine rough idle

P1509 CADILLAC Possible Causes

Faulty Idle Air Control (IAC),Idle Air Control Valve harness is open or shorted,Idle Air Control Valve circuit poor electrical connection

P1509 CADILLAC Description

With the engine runtime 2 minutes, closed throttle, Engine Coolant Temperature (ECT) input over 122??, Intake Air Temperature (IAT) over 62??, VSS under 3 mph, the Powertrain Control Module (PCM) detects that the Actual idle speed was 175 rpm higher than desired idle speed.