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Home >> Chevrolet >> 2004 >> Optra Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 2.0L (L34 GMDAT) - DTC P0496 To DTC P2422 >> DTC P2279 >> Test Description

Test Description

The numbers below refer to the step numbers in the diagnostic table.

  1. 5:  This step prompts the technician to check for any condition that can allow air to enter the engine. Any condition that can affect the idle speed of the engine must be repaired first, in order to enable the correct diagnosis of the DTC P2279.
  2. 6:  Deposits on the throttle valve can affect the air flow through the throttle body and into the engine.
Step Action Yes No
1 Did you perform the Diagnostic System Check - Engine Controls? Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Turn ON the ignition, with the engine OFF.
  2. Clear the DTC with a scan tool.
  3. Start the engine.
  4. Observe the DTC Info with a scan tool.
Did the DTC fail this ignition?		 Go to Step 3  Go to Step 4 
3 Did DTC P0506 or P0507 also set? Go to DTC P0506 or P0507  Go to Step 5 
4
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 Go to Step 5  Go to Intermittent Conditions
5 
  1. Inspect the engine for any of the following conditions:
    • A stuck or damaged throttle valve or throttle body
    • A vacuum or intake air leak
    • An evaporative emission (EVAP) system malfunction
    • An exhaust gas recirculation (EGR) system leak
    • Faulty positive crankcase ventilation (PCV) system operation
  2. Repair the condition, as necessary.
Did you find and correct a condition?		 Go to Step 8  Go to Step 6 
6  Inspect the throttle valve for excessive deposits. Clean as necessary. Refer to Throttle Body Inspection and Cleaning .
Did you find and correct a condition?		 Go to Step 8  Go to Step 7 
7
  1. Inspect the camshaft timing. Refer to Timing Belt Inspection in Engine Mechanical - 2.0L (L34 GMDAT).
  2. Repair the condition, as necessary.
Did you find and correct a condition?		 Go to Step 8  Go to Intermittent Conditions
8
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 Go to Step 2  Go to Step 9 
9 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 Go to Diagnostic Trouble Code (DTC) List System OK
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