If the replaced IAC was shorted, there is a possibility the POCM could have been damaged.
Here is a description of the problem and possible causes.
DTC P1506: IDLE AIR CONTROL SYSTEM - MALFUNCTION
DTC P1506 indicates PCM detected an engine idle speed more than desired RPM. Idle Air Control (IAC) valve controls engine idle 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 IAC valve through a specified duty cycle. The IAC valve responds by positioning to control amount of bypass air. PCM monitors engine RPM and increases or decreases IAC duty cycle in order to achieve desired RPM.
Possible causes are:
a) Vacuum leak.
B) Damaged IAC valve.
C) Damaged PCM.
D) Damaged throttle body.
E) IAC circuit short to GND.
F) IAC valve stuck open.
Tuesday, November 22nd, 2011 AT 11:42 AM