P0506 - Idle Air Control (IAC) System RPM Lower Than Expected
This P0506 code is one that's sometimes triggered on vehicles that have electronic
throttle control. That is, they don't have a regular throttle cable from the
accelerator pedal to the engine. They rely on sensors and electronics to control
the throttle. In this case, the P0506 DTC (diagnostic trouble code) is triggered
when the PCM (powertrain control module) detects an engine idle speed that is
lower than the desired (pre-programmed) RPM.
Most likely the only thing you'll notice is the idle speed is lower than normal
so it will likely be rougher. There are potentially other symptoms as well.
Of course, when trouble codes are set, the MIL (malfunction indicator lamp,
a.k.a. the check engine light) illuminates.
A P0506 DTC trouble code may be caused by one or more of the following:
- A vacuum leak
- An air restriction in the intake air path or exhuast
- A faulty positive crankcase ventilation (PCV) valve
- Damaged/failed/dirty throttle body
- Internal engine problem
- Failed PCM
This DTC is more of an informational code, so if there are any other codes
set, diagnose them first. If there are no other codes, inspect for vacuum leaks,
restrictions, and damage. If there are no symptoms other than the DTC itself,
just clear the code and see whether it returns.