Honda Civic Service Manual page 337

ldle Control System
DTC Troubleshooting
DTC P0505: ldle Control System Malfunction
NOTE: lf DTC P1519 is stored atthe same time as DTC
P0505, troubleshoot DTC P1519 first, then recheck for
DTC P0505.
1. Start the engine. Hold the engine at 3,000 rpm with
no load (in neutral) until the radiator fan comes on,
then let it idle,
2. Checkthe engine speed at idle with no,load
conditions: headlights, blower fan, rear defogger,
radiator fan, and air conditioner off.
Is the engine running at 750t50 rpm?
YES - Intermittent failure, system is OK at this
t r m e . I
NO lf the idle speed is less than 700 rpm, go to
step 3; if it's 800 rpm or higher, go to step 4.
3 . D i s c o n n e c t t h e i d l e a i r c o n t r o l { l A C ) v a l v e 3 P
connector.
Does the engine speed increase or fluctuate?
YES- Check the idle speed {see page 1 1-138). lf the
idle will not adjust properly, clean the passage in
the throttle body, and then adjust the idle. I
N O - R e p l a c e t h e I A C v a l v e . I
4. Turn the ignition switch OFF.
5. Remove the intake air duct from the throttle body.
6. Start the engine, and let it idle.
1 1 - 1 3 0
(
7 . P u t y o u r f i n g e r s o n t h e l o w e r p o n ( A ) i n t h e t h r o t t l e
oooy.
Does the engine stall?
Y E S C h e c k t h e i d l e s p e e d ( s e e p a g e 1 1 - 1 3 8 ) . l f i t ' s
out of specification, replace the IAC valve.l
NO With the throttle valve completely closed,
c h e c k f o r v a c u u m l e a k s , a n d r e p a i r a s n e c e s s a r y . l