DTC P0506: Idle Control System RPM Lower Than Expected <3.0L Engine>

CIRCUIT OPERATION
• The idle air control (IAC) motor power is supplied from the MFI relay (terminal 1).
• The PCM (terminals 14, 15, 28, 29) drives the stepper motor by sequentially turning "ON" the power transistors in the PCM and providing ground to the idle air control motor (terminals 1, 3, 4, 6).
TECHNICAL DESCRIPTION
• The amount of air taken in during idling is regulated by the opening and closing of the servo valve located in the air passage that bypasses the throttle body.
• If there is a malfunction of the IAC system, the actual engine speed will not be identical to the target engine speed.
• The PCM checks the difference between the actual engine speed and the target engine speed.
DTC SET CONDITIONS

Check Conditions
• Under the closed loop idle speed control.
• Engine coolant temperature is higher than 82°C (180°F).
• Battery positive voltage is higher than 10 volts.
• Power steering pressure switch: "OFF."
• Volumetric efficiency is lower than 40 percent.
• Barometric pressure is higher than 76 kPa (11 psi).
• Intake air temperature is higher than -10°C (14°F).

Judgment Criteria
• The actual idle speed is more than 100 r/min lower than the target idle speed for 12 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
• Idle air control motor failed.
• Open or shorted idle air control motor circuit, or loose connector.
• PCM failed.