DTC P0506: Idle Control System RPM Lower Than Expected

CIRCUIT OPERATION
• The idle air control (IAC) motor power is supplied from the MFI relay (terminal No. 1).
• The PCM (terminals No. 14, No. 15, No. 28, No. 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 No. 1, No. 3, No. 4, No. 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.
DESCRIPTIONS OF MONITOR METHODS
Difference between actual and target idle speed is over the specified value.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
• Misfire monitor
• Exhaust gas recirculation (EGR) system monitor
• Fuel system monitor

Sensor (The sensor below is determined to be normal)
• Volume airflow sensor
• Engine coolant temperature sensor
• Intake air temperature sensor
• Barometric pressure sensor
• Throttle position sensor
DTC SET CONDITIONS Logic Flow Chart


Check Conditions
• Under the closed loop idle speed control.
• Engine coolant temperature is more than approximately 77°C (171°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 (22.4 in.Hg).
• Intake air temperature is higher than -10° C (14° F).
• 60 seconds have elapsed from the start of the previous monitoring.
• Target idle air control motor position is more than 100 steps.

Judgment Criteria
• The actual idle speed is more than 100 r/min lower than the target idle speed for 12 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor .
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, harness damage or connector damage.
• Throttle valve area is dirty.
• PCM failed.