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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1076 (Engine Controls Diagnosis - 8.1L (DTC P0175 To P2610)) >> Diagnosis >> DTC P0172 or P0175 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 5:  If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
  2. 6:  An EVAP canister that is saturated will cause a rich condition. If the conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.
DTC P0172 or P0175

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
IMPORTANT: If any DTCs other than P0172 are set, refer to those DTCs before continuing.
  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?		 -13% Go to Step 3  Go to Diagnostic Aids
3
  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 4  Go to Step 5 
4
  1. Turn OFF engine.
  2. Visually and physically inspect the following items:
    • The evaporative emissions (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.
    • Check for objects blocking the throttle body.
Did you find and correct the condition?		 - Go to Step 7  Go to Step 6 
5 
  1. Turn OFF 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 and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 7  Go to Fuel System Diagnosis
6  Inspect for the following:
Did you find and correct the condition?		 - Go to Step 7  Go to Symptoms - Engine Mechanical in Engine Mechanical - 8.1L
7
IMPORTANT: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.
  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 8 
8 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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