Detection Condition

DTC P1506 indicates PCM detected an engine speed more than desired RPM. Idle Air Control (IAC) valve controls engine speed and provides a dashpot function. IAC valve meters intake air around throttle plate through a bypass within the IAC valve assembly and throttle body. PCM determines desired idle speed or bypass air and signals the IAC valve through a specified duty cycle. The IAC valve responds by positioning itself to control amount of bypass air. PCM monitors engine RPM and increases or decreases the IAC duty cycle in order to achieve desired RPM.