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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1857 (Engine Controls And Fuel - 3.5L (L66) - DTC P0030 To DTC P0222) >> DTC P0171 or P0174 >> Test Description

Test Description

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

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

  1. 1:  The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 2:  This step determines whether the fault is present.
  3. 4:  If DTC P0171 and P0174 are set at the same time, this indicates both banks of the engine are operating lean. Inspect the items that would cause both banks to operate lean.
  4. 5:  A vacuum leak causes DTC P0171 and P0174 to set at the same time. Inspect all areas of the engine for a vacuum leak. Also inspect the positive crankcase ventilation (PCV) valve for being the correct one for this application. Make sure that the engine oil fill cap is in place and that it is tight. Verify that the engine oil dip stick is fully seated.
  5. 8:  This step tests for inadequate fuel delivery from a fuel injector. The fault may be a fuel injector or the fuel injector electrical circuit.
DTC P0171 or P0174

Step Action Value(s) Yes No
1  Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 
IMPORTANT: If any DTCs are set, except P0171 and P0174, refer to those DTCs before proceeding with this diagnostic.
  1. Start the engine.
  2. Idle the engine at the normal operating temperature.
  3. Operate the vehicle until the scan tool indicates Closed Loop.
  4. Observe the Long Term FT parameter for bank 1 or bank 2 with a scan tool.
Does the scan tool display less than the specified value?		 18% Go to Step 3  Go to Step 4 
3
  1. Turn ignition ON, with the engine OFF.
  2. Observe the Freeze Frame/Failure Records for this DTC.
  3. Clear the DTCs with a scan tool.
  4. Turn OFF the ignition for 90 seconds.
  5. Start the engine.
  6. 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 4  Go to Diagnostic Aids In This Test
4  Are both banks of the engine operating lean? - Go to Step 5  Go to Step 6 
5  Visually and physically inspect for any of the following conditions:
Did you find and correct the condition?		 - Go to Step 11  Go to Step 7 
6 Visually and physically inspect for any of the following conditions:
  • Inspect for exhaust leaks, missing or loose exhaust hardware. Refer to Exhaust Leakage .
  • Inspect that the heated oxygen sensor (HO2S) is installed securely and the electrical connector is not contacting the exhaust system.
  • Inspect for an engine mechanical condition. Refer to Symptoms - Engine Mechanical .
  • Inspect for vacuum leaks that only affect one bank of the engine. For example, the intake manifold, the injector O-rings.

Did you find and correct the condition?		 - Go to Step 11  Go to Step 7 
7
IMPORTANT: When you have completed the fuel system diagnosis, return to this diagnostic.
Test fuel system for operating lean. Refer to Fuel System Diagnosis .Did you find and correct the condition?		 - Go to Step 11  Go to Step 8 
8  Test the fuel injectors for any of the following conditions:
Did you find and correct a condition?		 - Go to Step 11  Go to Step 9 
9 Test for an intermittent and for a poor connection at the appropriate HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 11  Go to Step 10 
10 Replace the HO2S. Refer to the appropriate procedure:
Did you complete the replacement?		 - Go to Step 11  -
11
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 90 seconds.
  3. Start the engine.
  4. Reset the fuel trim system with a scan tool.
  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 12 
12 In order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, operate the vehicle within the conditions for running and setting DTC P0420/0430 and verify that DTC P0420/0430 runs and passes. Refer to DTC P0420 or P0430 .
Does the DTC run and pass?		 - Go to Step 13  Go to DTC P0420 or P0430
13 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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