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Home >> Chevrolet >> 2006 >> Impala SS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 5.3L - DTC P0136 To DTC P0446 >> DTC P0172 >> Test Description

Test Description

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

  1. 7:  An evaporative emission (EVAP) canister that is saturated will cause a rich condition.
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 Are any DTCs other than DTC P0172 also set? - Go to Diagnostic Trouble Code (DTC) List - Vehicle Go to Step 3 
3
  1. Install scan tool.
  2. Start and idle the engine at the normal operating temperature in Closed Loop.
  3. Record the long term fuel trim data.
  4. Turn OFF the engine.
  5. Turn ON ignition, with the engine OFF.
  6. Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
Does the scan tool indicate that the long term fuel trim is less than the specified value?		 -17% Go to Step 4  Go to Diagnostic Aids
4
  1. Operate engine at idle.
  2. Observe HO2S parameters with a scan tool.
Does the scan tool indicate that the values are within the specified range and fluctuating?		 200-800 mV Go to Step 5  Go to Step 6 
5
  1. Turn OFF the engine.
  2. Visually and physically inspect the following items:
    • The evaporative emission (EVAP) lines and components for damage or blockage-Refer to Evaporative Emissions (EVAP) Hose Routing Diagram .
    • The inlet screen of the mass air flow (MAF) sensor for blockage
    • 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
    • Inspect for objects blocking the throttle body.
Did you find and correct the condition?		 - Go to Step 8  Go to Step 7 
6
  1. Turn OFF the engine.
  2. Inspect the heated oxygen sensor (HO2S) for proper installation.
  3. Inspect to ensure that the electrical connectors and the wires are secure and not contacting the exhaust system.
  4. Test for continuity between the signal circuit and the low reference circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor (HO2S) Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 8  Go to Fuel System Diagnosis
7  Inspect for the following:
Did you find and correct the condition?		 - Go to Step 8  Go to Symptoms - Engine Mechanical
8
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. 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 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 - Vehicle System OK
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