Subaru Legacy IV (2008 year). Manual - part 632
GD(H6DO)-148
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
CS:DTC P0506 IDLE AIR CONTROL SYSTEM RPM LOWER THAN EXPECTED
1. OUTLINE OF DIAGNOSIS
Detect the malfunction that actual engine speed is not close to target engine speed during idling. Judge as
NG when actual engine speed is not close to target engine speed during idling.
2. ENABLE CONDITION
3. GENERAL DRIVING CYCLE
Perform the diagnosis continuously at idling after warming up engine.
4. DIAGNOSTIC METHOD
• Abnormality Judgement
If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.
Time Needed for Diagnosis: 10 s × 3 time(s)
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.
• Normality Judgement
Judge as OK and clear the NG if the continuous time while the following conditions are established is more
than the predetermined time.
Time Needed for Diagnosis: 10 s
Secondary Parameters
Enable Conditions
Engine coolant temperature
t 75 °C (167 °F)
Battery voltage
t 10.9 V
Atmospheric pressure
t 75 kPa (563 mmHg,
22.2 inHg)
Fuel level
t 9.6
2 (2.54 US gal,
2.11 Imp gal)
Elapsed time after starting the engine
t 10.49 s
Feedback of ISC
In operation
Lambda value (left and right)
t 0.9
and
<
1.1
After switching air conditioner to ON/
OFF
t 5.1 s
After intake manifold pressure changes
by 4 kPa (30 mmHg, 1.2 inHg) or more.
> 5.1 s
Elapsed time after switching neutral
position switch to ON/OFF
> 5.1 s
Vehicle speed
0 km/h (0 MPH)
Judgement Value
Malfunction Criteria
Threshold Value
Actual engine speed — Targeted engine
speed
< –100 rpm
Feedback compensation for ISC
Max.
Judgement Value
Malfunction Criteria
Threshold Value
Actual engine speed — Targeted engine
speed
t –100 rpm