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DTC P0506: Idle Control System RPM Lower Than Expected
 
 
 
 
TECHNICAL DESCRIPTION
  • The amount of air taken in during idling is regulated by the opening and closing of the throttle valve.
  • The ECM 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 set 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)
  • Mass 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.
  • The engine coolant temperature is more than 41°C (106°F).
  • Battery positive voltage is more than 10 volts.
  • Barometric pressure is more than 76 kPa (22.4 in.Hg).
  • Intake air temperature is more than -10°C (14°F).
  • More than 3 seconds have passed from the end of the previous monitoring.
  • Target airflow rate is more than 14 g/sec (12 L/sec) when engine coolant temperature is more than 77°C (171°F).
  • Target airflow rate is more than 27 g/sec (23 L/sec) when engine coolant temperature is less than 77°C (171°F).
Judgment Criterion
  • The actual idle speed is less than the target idle speed by 100 r/min or more for 10 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 18 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Throttle valve area is dirty.
  • Throttle body assembly failed.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tool:
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: USB Cable
    • MB991910: Main Harness A
STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the diagnostic trouble code other than P0506 set?
Refer to, Diagnostic Trouble Code Chart .
Go to Step 2.
 
STEP 2. Check the throttle body. (throttle valve area)
Is the throttle valve area dirty?
Perform cleaning. Refer to, Throttle Body (throttle valve area) Cleaning . Then go to Step 4.
Go to Step 3.
 
STEP 3. Replace the throttle body assembly.
(1) Replace the throttle body assembly.
(2) Carry out test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 18 .
(3) Check the diagnostic trouble code (DTC).
Is DTC P0506 set?
Replace the ECM (Refer to, Removal and Installation ). Then go to Step 4.
The inspection is complete.
 
STEP 4. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 18 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0506 set?
Retry the troubleshooting.
The inspection is complete.