Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Service manual — part 264
EN(H4DOTC)(diag)-280
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CX:DTC P050A COLD START IDLE AIR CONTROL SYSTEM PERFORMANCE
DTC DETECTING CONDITION:
• Detected when 2 consecutive driving cycles with fault occur.
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-185, DTC P050A COLD START IDLE AIR CONTROL
SYSTEM PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Engine keeps running at higher speed than specified idle speed.
• Engine keeps running at a lower speed than the specified idle speed.
• Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-63,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-49, PROCE-
WIRING DIAGRAM:
• Engine electrical system, without SI-DRIVE <Ref. to WI-32, WITHOUT SI-DRIVE, WIRING DIAGRAM,
• Engine electrical system, with SI-DRIVE <Ref. to WI-48, WITH SI-DRIVE, WIRING DIAGRAM, Engine
ECM
EN-08718
#4
2
1
#3
2
1
#2
2
1
B21
#1
2
1
4
8
54
53
52
51
10
11
12
13
1 2
B21
E5
E5
E2
E6
E6
E16
E16
E17
E17
B134
1 2 3 4
12 13 14 15
5 6 7 8
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
35
34
37
36
39
38
41
40
43
42
44 45
47
46
49
48
51
50
53
52
54
B220
24
23
22
15A
B220
3
4
21
B134
31
30
32
29
34
33
21
20
19
18
17
16
28
27
26
15
14
13
12
11
25
23
22
24
10
3
4
9
1
2
8
7
6
5
B220
18
19
6
7
4
3
5
2
1
12
11
10
9
8
40
36 39
38
37
34
33
35
32
28 31
30
29
23
22
21
20
26
25
24
27
17
16
15
14
13
E
SBF-7
MAIN RELAY
FUSE
(RELAY BLOCK)
FUEL INJECTOR
BATTERY
EN(H4DOTC)(diag)-281
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
Check
Yes
No
1
CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?
2
CHECK ENGINE OIL.
Is there a proper amount of
engine oil?
Replace engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.>
3
CHECK EXHAUST SYSTEM.
Are there holes or loose bolts
on exhaust system?
Repair the exhaust
system.
ECM
EN-08727
5
6
7
8
2
1
9
4
3
10
24
22 23
25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 34
29
32
30 31
B136
C:
B134
A:
36
35
34
40
B17
B7
D3
A29
6
E2
B21
A1
8
C4
A2
8
6
4
25
*
*
B122
24
3
8
39
2
8
A2
A1
A19
A6
A3
D1
A4
3
E57
2
1
5
B134
B220
B220
31
29
32
A:
B137
B136
D:
C:
B135
B:
*
30
21
22
15A
B220
3
4
B135
B:
35
34
33
32
31
30
29
21
20
19
18
17
16
28
27
26
15
14
13
12
11
25
23
22
24
10
3
4
9
1
2
8
7
6
5
B220
18
19
6
7
4
3
5
2
1
12
11
10
9
8
40
36 39
38
37
34
33
35
32
28 31
30
29
23
22
21
20
26
25
24
27
17
16
15
14
13
B122
8
7
6
5
4
3
2
1
B21
33
32
31
30
29
28
27
26
47
46
45
44
43
42
54
53
52
51
50
49
48
41
40
39
38
37
36
35
34
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
D: B137
26
25
24
23
22
18
28
27
17
16
15
14
13
31
30
29
21
20
19
12
11
10
4
3
6
5
9
8
7
2
1
E57
6
5
4
3
2
1
35
34
33
32
7
26
25
24
23
22
18
28
27
17
16
15
14
13
31
30
29
21
20
19
12
11
10
4
3
6
5
9
8
2
1
E
E
E
SBF-7
FUSE
(RELAY BLOCK)
MAIN RELAY
ELECTRONIC THROTTLE
CONTROL RELAY
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
EN(H4DOTC)(diag)-282
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
4
CHECK AIR INTAKE SYSTEM.
Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
5
CHECK FUEL PRESSURE.
WARNING:
Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:
Be careful not to spill fuel.
Measure the fuel pressure while disconnecting
pressure regulator vacuum hose from intake
manifold. <Ref. to ME(STI)-25, INSPECTION,
Fuel Pressure.> <Ref. to ME(w/o STI)-24,
INSPECTION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Is the measured value 284 —
314 kPa (2.9 — 3.2 kg/cm
2
, 41
— 46 psi)?
Check the fuel
pump and fuel
delivery line.
• Models without
SI-DRIVE <Ref. to
FU(w/o STI)-79,
INSPECTION,
Fuel Pump.> <Ref.
to FU(w/o STI)-93,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
• Models with SI-
DRIVE <Ref. to
FU(STI)-81,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-97,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
6
CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.> <Ref. to
ME(w/o STI)-24, INSPECTION, Fuel Pres-
sure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
• If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
• If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.
Is the measured value 230 —
260 kPa (2.4 — 2.7 kg/cm
2
, 33
— 38 psi)?
Check the fuel
pump and fuel
delivery line.
• Models without
SI-DRIVE <Ref. to
FU(w/o STI)-79,
INSPECTION,
Fuel Pump.> <Ref.
to FU(w/o STI)-93,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
• Models with SI-
DRIVE <Ref. to
FU(STI)-81,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-97,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
Step
Check
Yes
No
EN(H4DOTC)(diag)-283
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
7
CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant
Temp.» 75°C (167°F) or more?
8
CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mass Air Flow» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mass Air Flow»
2.0 — 5.0 g/s (0.26 — 0.66 lb/m)?
9
CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?
Step
Check
Yes
No
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