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Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different car >> Section 692 (Engine Controls And Fuel - 2.0L - DTC P0125 To DTC P0327) >> DTC P0172 >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to the step number on the diagnostic table.

  1. 8:  If conditions were not corrected, a worn cam, worn intake or exhaust valves or other engine mechanical failure may be at fault.
DTC P0172

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to DIAGNOSTIC SYSTEM CHECK - VEHICLE
2
IMPORTANT: Disregard any transmission symptoms, antilock brake system (ABS) indicators, and traction control system (TCS) indicators until any fuel trim faults are repaired. A fuel trim fault may cause default actions such as harsh shifts and illumination of the ABS/TCS indicators.
Are any DTCs other than DTC P0172 also set?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle Go to Step 3 
3
  1. Install a scan tool.
  2. Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
  3. Select Fuel Trim Data parameter.
  4. Start the engine.
  5. Observe the Long Term FT parameter with a scan tool.
Is the Long Term FT parameter less than the specified value?		 -19% Go to Step 4  Go to Diagnostic Aids
4
  1. Start the engine.
  2. Allow the engine to reach operating temperature.
  3. Put the transmission in the NEUTRAL position.
  4. Turn OFF all of the accessories.
  5. Allow the engine to idle.
  6. Observe the Manifold Absolute Pressure (MAP) sensor parameter with a scan tool.
Is the MAP sensor parameter within the specified range?		 19-42 kPa Go to Step 5  Go to DTC P0106
5
  1. Operate the engine at idle.
  2. Observe the Heated Oxygen Sensor (HO2S) parameters with a scan tool.
Does the scan tool indicate that the values are within the specified range and fluctuating?		 40-900 mV Go to Step 6  Go to Step 7 
6
  1. Turn OFF the engine.
  2. Visually and physically inspect the following items:
    • The vacuum hoses for splits, kinks, and proper connections-Refer to Emission Hose Routing Diagram .
    • The air intake duct for being collapsed or restricted
    • The air filter for being dirty or restricted
    • For objects blocking the throttle body
Did you find and correct the condition?		 - Go to Step 9  Go to Step 8 
7
  1. Turn OFF the engine.
  2. Inspect for the following conditions:
    • The HO2S for proper installation
    • The electrical connectors and wires are secured and not contacting the exhaust system
    • The HO2S signal circuit for a short to voltage
  3. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 9  Go to Fuel System Diagnosis
8  Inspect for the following:
Did you find and correct the condition?		 - Go to Step 9  Go to Symptoms - Engine Mechanical
9
IMPORTANT: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.
  1. Turn ON the ignition, with the engine OFF.
    2. IMPORTANT: Do not clear codes with the engine running. The codes may reset in the same ignition cycle.
  2. Clear the DTCs with a scan tool.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. 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 10 
10 To verify that the performance of the catalytic converter has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420. Refer to DTC P0420 .
Did you complete the procedure?		 - Go to Step 11  Go to DTC P0420
11 Observe the Capture Info with a scan tool.
Have any other DTCs not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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