Speed, idle & inputs · Powertrain · generic (SAE-defined)
P0506: Idle Air Control System RPM Lower Than Expected
P0506 means the engine is idling slower than the engine computer's target speed, even after it tried to correct the idle.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0506 sets
The powertrain control module (PCM) compares actual idle speed with its target while the vehicle is stopped and warm. If idle remains below the target by more than a calibrated amount for a set time, even with the idle control at its correction limit, the PCM sets P0506. Targets and limits vary by manufacturer.
Common causes of P0506
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Carbon-restricted throttle body or IAC passage
- Sticking or failing idle air control valve
- Faulty electronic throttle body
- Restricted air intake or very dirty air filter
- Engine mechanical issues such as low compression
- Restricted exhaust
P0506 symptoms
- Check engine light on
- Low or rough idle
- Vibration at idle
- Stalling, especially with air conditioning on
How P0506 is diagnosed
- Check for related codes such as misfires, throttle codes, or lean codes
- Compare target and actual idle speed in live data
- Inspect the air filter and intake for restrictions
- Clean the throttle body and check IAC operation
- Check for exhaust restriction if idle is low and power is poor
- Perform an idle relearn after repairs
Typical fixes for P0506
- Clean the throttle body and idle passages
- Replace the IAC valve or electronic throttle body
- Replace a clogged air filter
- Address engine mechanical or exhaust restriction issues
- Perform an idle relearn
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Commonly reported on some GM vehicles with electronic throttle bodies. Definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0506 FAQ
What does code P0506 mean?
P0506 means the engine is idling slower than the engine computer's target speed, even after it tried to correct the idle. The standard definition is "Idle Air Control System RPM Lower Than Expected."
Can I drive with a P0506 code?
Usually yes, but a low idle can lead to rough running and stalling, especially with accessories like air conditioning on. If the engine stalls, avoid driving in traffic until it is fixed.
Can a dirty throttle body cause P0506?
Yes. Carbon buildup around the throttle plate reduces idle airflow, so the engine struggles to reach its target idle speed.
Do I need a software update for P0506?
Some manufacturers have released updates that revise idle control logic. Check factory service information for your vehicle.
Keep researching
More speed, idle & inputs codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.