Dtc P0505 Idle Air Control (Iac) Malfunction; Circuit Description; Diagnostic Aids - Briggs & Stratton VANGUARD M490000 Repair Manual

DTC P0505 IDLE AIR CONTROL (IAC) MALFUNCTION

Circuit Description

The ECM controls idle speed to a calibrated RPM based
on sensor inputs and actual engine RPM. The ECM uses
four circuits to move the IAC valve.
The movement of the IAC valve varies the amount of air
flow bypassing the throttle plates. The ECM controls idle
speed by determining the position of the IAC valve.

Diagnostic Aids

Check for the following conditions:
1. Poor connection or damaged harness. Inspect
the ECM harness and connectors for improper
mating, broken locks, improperly formed or damaged
terminals, poor terminal to wire connection and
damaged harness.
2. Check for vacuum leaks, disconnected or brittle
vacuum hoses, cuts, etc. Examine manifold and
throttle body gaskets for proper seal. Check for
cracked intake manifold.
3. Check for poor connections, opens or shorts to
ground in the IAC circuit.
4. Check for a stuck IAC valve that will not respond
to the ECM, a throttle stop screw that has been
tampered with, or a damaged throttle body or linkage.
Always clear DTCs after performing repairs.
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