Fault Family System: Powertrain (P-Codes) 11 SAE Codes

Idle Air Control System

Diagnostic & Technical Explanation

Code P0505 (Idle Control System) sets when commanded idle RPM (or, on diesel platforms, idle fuel quantity) does not match the ECM's target, or the idle air control actuator's circuit reports an open/out-of-range condition. Root causes are a carbon-fouled IAC valve or throttle bore restricting airflow, an unmetered vacuum/intake air leak that pushes idle high, a sticking throttle plate, or a failed IAC motor/solenoid and its wiring.

These 11 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 11 times.

Codes in this family (11)

Code	Definition	Repair coverage
P0505	Idle Control System	4 ranked fixes
P0506	Idle Control System RPM - Lower Than Expected	4 ranked fixes
P0507	Idle Control System RPM - Higher Than Expected	4 ranked fixes
P0508	Idle Air Control System Circuit Low	4 ranked fixes
P0509	Idle Air Control System Circuit High	4 ranked fixes
P050A	Cold Start Idle Control System Performance	4 ranked fixes
P0511	Idle Air Control Circuit	4 ranked fixes
P0518	Idle Air Control Circuit Intermittent	4 ranked fixes
P0519	Idle Air Control System Performance	4 ranked fixes
P054E	Idle Control System - Fuel Quantity Lower Than Expected	4 ranked fixes
P054F	Idle Control System - Fuel Quantity Higher Than Expected	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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