Briggs & Stratton VANGUARD 810 EFI Repair Manual page 64

60
DTC P0505 Idle Air Control (IAC) Malfunction
Circuit Description
The ECM controls idle speed to a calibrated
RPM based on sensor inputs and actual en-
gine RPM. The ECM uses four circuits to move
the IAC valve.
The movement of the IAC valve varies the
amount of air fl ow bypassing the throttle
plates. The ECM controls idle speed by deter-
mining the position of the IAC valve.
Diagnostic Aids
Check for the following items:
1. Poor connection or damaged harness.
Inspect the ECM harness and connectors
for improper mating, broken locks, improp-
erly formed or damaged terminals, poor
terminal to wire connection and damaged
harness.
A
C
BLUE/RED
BLUE/GREEN
J1 13 J1 11
IAC A
IAC B
Low
Low
Control Control
Section 2: Troubleshooting DTCs
B
D
BLUE/GRAY
BLUE/BROWN
J1 12 J1 01
IAC B IAC A
High High
Control Control
2. Check for vacuum leaks, disconnected or
brittle vacuum hoses, cuts, etc. Examine
manifold and throttle body gaskets for prop-
er seal. Check for cracked intake manifold.
3. Check for poor connections, opens or short
to grounds 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 dam-
aged throttle body or linkage.
Always clear DTCs after performing repairs.
IAC
ECM