What does code P1509 mean?

Q: What does code P1509 mean?

IAC System High RPM. P1509 on a GM vehicle means the powertrain control module (PCM) commanded the idle air control (IAC) valve to manage idle speed, but the engine speed stayed higher than the expected target for the commanded pintle position. The PCM compares actual RPM from the crankshaft position sensor against the idle speed it expects for the current coolant temperature and load, and it sets this code when the engine runs too fast at idle despite the IAC valve being driven toward a closed position.

DTC codes / GM codes / P1509

P1509 · GMIAC System High RPM

P1509 on a GM vehicle means the powertrain control module (PCM) commanded the idle air control (IAC) valve to manage idle speed, but the engine speed stayed higher than the expected target for the commanded pintle position. The PCM compares actual RPM from the crankshaft position sensor against the idle speed it expects for the current coolant temperature and load, and it sets this code when the engine runs too fast at idle despite the IAC valve being driven toward a closed position.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.