The 2016 Infiniti QX60 should idle smoothly whether in park or stopped in drive, but rough idle accompanied by P0505 indicates the idle control system requires attention. Understanding what triggers this code helps target appropriate repairs.
Understanding P0505
P0505 indicates the ECU detects a malfunction in the idle air control system. Modern vehicles like the QX60 use electronic throttle control for all airflow management including idle speed. When the system cannot maintain target idle RPM, this code sets.
Common Causes of Rough Idle with P0505
Carbon deposits on the throttle body bore prevent smooth blade positioning. Vacuum leaks allow unmetered air to enter, confusing idle calculations. Electronic throttle issues including motor or position sensor problems. MAF sensor contamination causes incorrect airflow calculation. Air leaks around the intake manifold gaskets.
QX60-Specific Considerations
The VQ35DE V6 in the QX60 uses variable valve timing (VVEL) that affects idle quality if malfunctioning. The CVT's interaction with engine management can make idle issues more noticeable when stopped in drive. System integration means related codes should be investigated together.
Diagnostic Approach
Inspect throttle body for carbon buildup affecting blade movement. Test for vacuum leaks using smoke testing. Check MAF sensor for contamination. Monitor idle control data through diagnostic scanner. Clean throttle body and perform relearn procedure after service.