LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2009 >> SC 430 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (Diagnostic Codes (P0351-U0001) - Circuit Tests) >> SFI System >> DTC P050A: Cold Start Idle Air Control System Performance >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P050A: Cold Start Idle Air Control System Performance: Procedure

  1. CHECK DTCS 

    Result

    Any other DTCs are not set.

    NG → GO TO DIAGNOSTIC TROUBLE CODE CHART 

    OK: Go to next step 

  2. READ SHORT-TERM AND LONG-TERM FUEL TRIMS 

    HINT: 

    The total of the short-term fuel trim (Short FT) and long-term fuel trim (Long FT) is used to discover a problem in the induction system (between air cleaner and intake manifold).

    1. Allow the engine to idle.
    2. Enter the following menus: Powertrain / Engine and ECT / Data List.
    3. Read the value of Short FT #1 and Long FT #1 (bank 1).
    4. Read the value of Short FT #2 and Long FT #2 (bank 2).

      Result

      Total of Short FT and Long FT is between -20% and 20%

    NG → See step   4 

    OK: Go to next step 

  3. CHECK THROTTLE BODY 
    1. Check for deposits around the throttle valve and throttle valve condition.

      Result

      No deposits around throttle valve and throttle valve moves smoothly.

    OK → See step   9 

    NG → See step   8 

  4. CHECK VVT SYSTEM 
    1. Allow the engine to idle with the engine warmed up.
    2. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the VVT System (Bank 1) or Control the VVT System (Bank 2).
    3. Turn on Control the VVT System (Bank 1) (or Control the VVT System (Bank 2)) to advance the valve timing.
    4. Check the engine condition.

      Result

      The engine stalls or idles roughly when Control the VVT System is ON. (VVT system is OK)

    NG → See step   10 

    OK: Go to next step 

  5. CHECK PCV SYSTEM 
    1. Allow the engine to idle.
    2. Pinch the positive crankcase ventilation (PCV) hose.
    3. Check the engine RPM.

      Result

      The engine RPM rises when the PCV hose is pinched.

    NG → See step   11 

    OK: Go to next step 

  6. CHECK AIR CLEANER FILTER 
    1. Visually check that the air cleaner filter is not excessively contaminated with dirt or oil.

    NG → See step   12 

    OK: Go to next step 

  7. CHECK AIR INDUCTION SYSTEM 
    1. Check the air induction system for vacuum leakage.

    OK → See step   14 

    NG → See step   13 

  8. REPAIR OR REPLACE THROTTLE BODY 

    NEXT → See step   15 

  9. REPLACE ECM 

    NEXT → See step   15 

  10. CHECK AND REPAIR VVT SYSTEM 

    NEXT → See step   15 

  11. REPAIR OR REPLACE PCV HOSE 

    NEXT → See step   15 

  12. REPLACE AIR CLEANER FILTER 

    NEXT → See step   15 

  13. REPAIR OR REPLACE AIR INDUCTION SYSTEM 

    NEXT → See step   15 

  14. REPLACE MASS AIR FLOW METER 

    NEXT → See step   15 

  15. CHECK DTCS 
    1. Check that the engine coolant temperature is -10 to 50°C (14 to 122°F).
    2. Clear the DTC.
    3. Enter the check mode using the Techstream.
    4. Allow the engine to idle for 1 minute.
    5. Check that no DTC is present.

    NEXT → END 

scientia non olet · About LEMON Manuals