DTC P050A: Cold Start Idle Control System Performance: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

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.

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .

   Read the engine DTC using the Subaru Select Monitor or general scan tool. Ref. to ENGINE (DIAGNOSTICS) (H6DO)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

   Is other than DTC P050A displayed? (Current malfunction)

   Yes  Check the appropriate DTC using the "List of Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H6DO)>LIST OF DIAGNOSTIC TROUBLE CODE (DTC) .

   No  Go to  2 .

2. CHECK ENGINE OIL  .

   Check the engine oil.

   Is there a proper amount of engine oil?

   Yes  Go to  3 .

   No  Replace engine oil. Ref. to LUBRICATION (H6DO)>ENGINE OIL>REPLACEMENT .

3. CHECK EXHAUST SYSTEM  .

   Check the exhaust system.

   Are there holes or loose bolts on exhaust system?

   Yes  Repair the exhaust system.

   No  Go to  4 .

4. CHECK AIR INTAKE SYSTEM  .

   Check the air intake system.

   Are there holes, loose bolts or disconnection of hose on air intake system?

   Yes  Repair the air intake system.

   No  Go to  5 .

5. CHECK FUEL PRESSURE  .
   WARNING: Place "NO OPEN FLAMES" signs near the working area.
   CAUTION:

   • Be careful not to spill fuel.
   • Before attaching/detaching a fuel pressure gauge, release the fuel pressure.

   Measure the fuel pressure. Ref. to MECHANICAL (H6DO)>FUEL PRESSURE>INSPECTION .

   Is the measured value 340 - 400 kPa (3.5 - 4.1 kgf/cm2, 49 - 58 psi)?

   Yes  Go to  6 .

   No  Check the fuel pump and fuel delivery line. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>FUEL PUMP>INSPECTION . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>FUEL DELIVERY AND EVAPORATION LINES>INSPECTION .

6. 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 "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (H6DO)>SUBARU SELECT MONITOR .

   • 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?

   Yes  Go to  7 .

   No  Replace the engine coolant temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>ENGINE COOLANT TEMPERATURE SENSOR .

7. 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 select lever in "P" range or "N" range.
   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 "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (H6DO)>SUBARU SELECT MONITOR .

   • 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)?

   Yes  Go to  8 .

   No  Replace the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .

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 select lever in "P" range or "N" range.
   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 "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (H6DO)>SUBARU SELECT MONITOR .

   • 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)?

   Yes  Go to  9 .

   No  Check the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .

9. CHECK OUTPUT SIGNAL OF ECM  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between ECM and chassis ground on faulty cylinders.

   Connector & terminal 

   #1 (E158) No. 23 (+) - Chassis ground (-):

   #2 (E158) No. 8 (+) - Chassis ground (-):

   #3 (E158) No. 9 (+) - Chassis ground (-):

   #4 (E158) No. 22 (+) - Chassis ground (-):

   #5 (E158) No. 52 (+) - Chassis ground (-):

   #6 (E158) No. 13 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes  Go to  14 .

   No  Go to  10 .

10. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from fuel injector on faulty cylinders.
    3. Measure the resistance between fuel injector connector and engine ground on faulty cylinders.

    Connector & terminal 

    #1 (E5) No. 2 - Engine ground:

    #2 (E16) No. 2 - Engine ground:

    #3 (E6) No. 2 - Engine ground:

    #4 (E17) No. 2 - Engine ground:

    #5 (E43) No. 2 - Engine ground:

    #6 (E44) No. 2 - Engine ground:

    Is the resistance 1 MΩ or more?

    Yes  Go to  11 .

    No  Repair the short circuit to ground in harness between ECM connector and fuel injector.

11. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR  .

    Measure the resistance of harness between ECM and fuel injector on faulty cylinders.

    Connector & terminal 

    #1 (E158) No. 23 - (E5) No. 2:

    #2 (E158) No. 8 - (E16) No. 2:

    #3 (E158) No. 9 - (E6) No. 2:

    #4 (E158) No. 22 - (E17) No. 2:

    #5 (E158) No. 52 - (E43) No. 2:

    #6 (E158) No. 13 - (E44) No. 2:

    Is the resistance less than 1 Ω?

    Yes  Go to  12 .

    No  Repair the open circuit of the harness between the ECM connector and fuel injector connector.

12. CHECK FUEL INJECTOR  .

    Check the fuel injector on faulty cylinder. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>FUEL INJECTOR>INSPECTION .

    Is the check result OK?

    Yes  Go to  13 .

    No  Replace the faulty fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>FUEL INJECTOR .

13. CHECK POWER SUPPLY LINE  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage between fuel injector and engine ground on faulty cylinders.

    Connector & terminal 

    #1 (E5) No. 1 (+) - Engine ground (-):

    #2 (E16) No. 1 (+) - Engine ground (-):

    #3 (E6) No. 1 (+) - Engine ground (-):

    #4 (E17) No. 1 (+) - Engine ground (-):

    #5 (E43) No. 1 (+) - Engine ground (-):

    #6 (E44) No. 1 (+) - Engine ground (-):

    Is the voltage 10 V or more?

    Yes  Repair the poor contact of all connectors in fuel injector circuit.

    No  Repair the harness and connector.

    NOTE: In this case, repair the following item:

    • Open circuit in harness between the main relay and fuel injector on faulty cylinders
    • Poor contact of coupling connector
    • Poor contact of main relay connector
14. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from fuel injector on faulty cylinders.
    3. Turn the ignition switch to ON.
    4. Measure the voltage between ECM and chassis ground on faulty cylinders.

    Connector & terminal 

    #1 (E158) No. 23 (+) - Chassis ground (-):

    #2 (E158) No. 8 (+) - Chassis ground (-):

    #3 (E158) No. 9 (+) - Chassis ground (-):

    #4 (E158) No. 22 (+) - Chassis ground (-):

    #5 (E158) No. 52 (+) - Chassis ground (-):

    #6 (E158) No. 13 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes  Repair the short circuit to power in harness between ECM connector and fuel injector.

    No  Go to  15 .

15. CHECK FUEL INJECTOR  .
    1. Turn the ignition switch to OFF.
    2. Check the fuel injector on faulty cylinder. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>FUEL INJECTOR>INSPECTION .

    Is the check result OK?

    Yes  Go to  16 .

    No  Replace the faulty fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>FUEL INJECTOR .

16. CHECK INSTALLATION OF CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR  .

    Check installation condition of the camshaft position sensor and crankshaft position sensor.

    Is the camshaft position sensor or crankshaft position sensor loosely installed?

    Yes  Tighten the camshaft position sensor or crankshaft position sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>CAMSHAFT POSITION SENSOR>INSTALLATION . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>CRANKSHAFT POSITION SENSOR>INSTALLATION .

    No  Go to  17 .

17. CHECK CRANKSHAFT POSITION SENSOR PLATE  .

    Check the crankshaft position sensor plate.

    Is the crank sprocket rusted or the teeth of crankshaft position sensor plate broken?

    Yes  Replace the crankshaft position sensor plate. Ref. to MECHANICAL (H6DO)>CYLINDER BLOCK .

    No  Go to  18 .

18. CHECK INSTALLATION CONDITION OF TIMING CHAIN  .

    Turn the crankshaft using ST, and align the alignment mark on crank sprocket with alignment mark on cylinder block.

    ST 18252AA000 CRANKSHAFT SOCKET 

    Is the timing chain dislocated from its proper position?

    Yes  Correct the installation condition of timing chain. Ref. to MECHANICAL (H6DO)>TIMING CHAIN ASSEMBLY .

    No  Go to  19 .

19. CHECK ELECTRONIC THROTTLE CONTROL RELAY  .
    1. Turn the ignition switch to OFF.
    2. Remove the electronic throttle control relay.
    3. Connect the battery to terminals No. 20 and No. 21 of electronic throttle control relay.
    4. Measure the resistance between electronic throttle control relay terminals.

    Terminals 

    No. 22 - No. 23:

    Is the resistance less than 1 Ω?

    Yes  Go to  20 .

    No  Replace the electronic throttle control relay. Ref. to ENGINE (DIAGNOSTICS) (H6DO)>ELECTRICAL COMPONENT LOCATION .

20. CHECK POWER SUPPLY OF ELECTRONIC THROTTLE CONTROL RELAY  .

    Measure the voltage between electronic throttle control relay connector and chassis ground.

    Connector & terminal 

    (B48) No. 22 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes  Go to  21 .

    No  Repair the open or short to ground in the power supply circuit.

21. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL RELAY  .
    1. Disconnect the connector from ECM.
    2. Turn the ignition switch to ON.
    3. Measure the voltage between electronic throttle control relay connector and chassis ground.

    Connector & terminal 

    (B48) No. 20 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes  Repair the short circuit to power in the harness between ECM connector and electronic throttle control relay.

    No  Go to  22 .

22. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL RELAY  .
    1. Turn the ignition switch to OFF.
    2. Measure the resistance between electronic throttle control relay connector and chassis ground.

    Connector & terminal 

    (B48) No. 20 - Chassis ground:

    (B48) No. 23 - Chassis ground:

    Is the resistance 1 MΩ or more?

    Yes  Go to  23 .

    No  Repair the short circuit to ground in harness between ECM connector and electronic throttle control relay.

23. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL RELAY  .

    Measure the resistance between ECM connector and electronic throttle control relay connector.

    Connector & terminal 

    (B134) No. 65 - (B48) No. 20:

    (B134) No. 13 - (B48) No. 23:

    Is the resistance less than 1 Ω?

    Yes  Go to  24 .

    No  Repair the open circuit in harness between ECM connector and electronic throttle control relay.

24. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Disconnect the connectors from electronic throttle control.
    4. Measure the resistance between ECM connector and chassis ground.

    Connector & terminal 

    (E158) No. 32 - Chassis ground:

    (E158) No. 29 - Chassis ground:

    (E158) No. 29 - (E158) No. 19:

    (E158) No. 31 - Chassis ground:

    (E158) No. 31 - (E158) No. 19:

    Is the resistance 1 MΩ or more?

    Yes  Go to  25 .

    No  Repair the ground short circuit of harness between ECM connector and electronic throttle control connector.

25. CHECK SHORT CIRCUIT INSIDE THE ECM  .
    1. Connect the connector to ECM.
    2. Measure the resistance between electronic throttle control connector and engine ground.

    Connector & terminal 

    (E57) No. 6 - Engine ground:

    (E57) No. 4 - Engine ground:

    Is the resistance 1 MΩ or more?

    Yes  Go to  26 .

    No  Repair the ground short circuit of harness between ECM connector and electronic throttle control connector. Replace the ECM if defective. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>ENGINE CONTROL MODULE (ECM) .

26. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL  .
    1. Disconnect the connector from ECM.
    2. Measure the resistance of harness between ECM connector and electronic throttle control connector.

    Connector & terminal 

    (E158) No. 29 - (E57) No. 6:

    (E158) No. 31 - (E57) No. 4:

    (E158) No. 34 - (E57) No. 3:

    Is the resistance less than 1 Ω?

    Yes  Go to  27 .

    No  Repair the open circuit of harness between ECM connector and electronic throttle control connector.

27. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL  .
    1. Connect the connector to ECM.
    2. Measure the resistance between electronic throttle control connector and engine ground.

    Connector & terminal 

    (E57) No. 3 - Engine ground:

    Is the resistance less than 5 Ω?

    Yes  Go to  28 .

    No  Repair the harness and connector.

    NOTE: In this case, repair the following item:

    • Open circuit of harness between ECM connector and engine ground
    • Poor contact of ECM connector
28. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage between electronic throttle control connector and engine ground.

    Connector & terminal 

    (E57) No. 6 (+) - Engine ground (-):

    (E57) No. 4 (+) - Engine ground (-):

    Is the voltage 5 V or more?

    Yes  Repair the short circuit to power in the harness between ECM connector and electronic throttle control connector.

    No  Go to  29 .

29. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Measure the resistance between ECM connectors.

    Connector & terminal 

    (E158) No. 32 - (E158) No. 29:

    (E158) No. 32 - (E158) No. 31:

    Is the resistance 1 MΩ or more?

    Yes  Go to  30 .

    No  Repair the short circuit to power in the harness between ECM connector and electronic throttle control connector.

30. CHECK SENSOR OUTPUT  .
    1. Connect all connectors.
    2. Turn the ignition switch to ON.
    3. Read the value of «Main-Throttle Sensor» using Subaru Select Monitor.
    NOTE: For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (H6DO)>SUBARU SELECT MONITOR .

    Is the value of «Main-Throttle Sensor» 0.81 - 0.87 V?

    Yes  Go to  31 .

    No  Repair the poor contact of electronic throttle control connector. Replace the electronic throttle control if defective. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>THROTTLE BODY .

31. CHECK SENSOR OUTPUT  .

    Read the value of «Sub-Throttle Sensor» using Subaru Select Monitor.

    NOTE: For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (H6DO)>SUBARU SELECT MONITOR .

    Is the value of «Sub-Throttle Sensor» 1.64 - 1.70 V?

    Yes  Go to  32 .

    No  Repair the poor contact of electronic throttle control connector. Replace the electronic throttle control if defective. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>THROTTLE BODY .

32. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL MOTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Disconnect the connectors from electronic throttle control.
    4. Measure the resistance between ECM connector and electronic throttle control connector.

    Connector & terminal 

    (E158) No. 1 - (E57) No. 1:

    (E158) No. 14 - (E57) No. 2:

    Is the resistance less than 1 Ω?

    Yes  Go to  33 .

    No  Repair the open circuit of harness between ECM connector and electronic throttle control connector.

33. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL MOTOR  .
    1. Connect the connector to ECM.
    2. Turn the ignition switch to ON.
    3. Measure the voltage between electronic throttle control connector and engine ground.

    Connector & terminal 

    (E57) No. 2 (+) - Engine ground (-):

    (E57) No. 1 (+) - Engine ground (-):

    Is the voltage 5 V or more?

    Yes  Repair the short circuit to power in the harness between ECM connector and electronic throttle control.

    No  Go to  34 .

34. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL MOTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Measure the resistance between electronic throttle control connector and engine ground.

    Connector & terminal 

    (E57) No. 2 - Engine ground:

    (E57) No. 1 - Engine ground:

    Is the resistance 1 MΩ or more?

    Yes  Go to  35 .

    No  Repair the short circuit to ground in harness between ECM connector and electronic throttle control.

35. CHECK ELECTRONIC THROTTLE CONTROL MOTOR HARNESS  .

    Measure the resistance between electronic throttle control connectors.

    Connector & terminal 

    (E57) No. 2 - (E57) No. 1:

    Is the resistance 1 MΩ or more?

    Yes  Go to  36 .

    No  Repair the short circuit in harness between ECM connector and electronic throttle control.

36. CHECK ELECTRONIC THROTTLE CONTROL GROUND CIRCUIT  .

    Measure the resistance between ECM connector and chassis ground.

    Connector & terminal 

    (E158) No. 60 - Chassis ground:

    (E158) No. 61 - Chassis ground:

    (E158) No. 62 - Chassis ground:

    (E158) No. 63 - Chassis ground:

    (E158) No. 64 - Chassis ground:

    (E158) No. 65 - Chassis ground:

    Is the resistance less than 5 Ω?

    Yes  Go to  37 .

    No  Repair the open circuit in harness between ECM connector and engine ground.

37. CHECK ELECTRONIC THROTTLE CONTROL  .

    Measure the resistance between electronic throttle control terminals.

    Terminals 

    No. 2 - No. 1:

    Is the resistance 50 Ω or less?

    Yes  Go to  38 .

    No  Replace the electronic throttle control. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>THROTTLE BODY .

38. CHECK ELECTRONIC THROTTLE CONTROL  .

    Move the throttle valve to the fully opened and fully closed positions with fingers.

    Check that the valve returns to the specified position when releasing fingers.

    Does the valve return to the specified position? Specified value: 3 mm (0.12 in) from fully closed position

    Yes  Repair the poor contact of ECM connector.

    No  Replace the electronic throttle control. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H6DO)>THROTTLE BODY .