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Home >> Cadillac >> 2004 >> CTS Base, 3.2 N >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 23 (Engine Controls - 3.6L - Diagnosis (DTC P1551 - P2189)) >> Diagnosis >> DTC P2177 or P2179 >> Test Description

Test Description

WARNING: This page is about a different variant/trim than selected.

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

  1. 2:  This step determines if there is a current condition.
  2. 4:  If DTC P2177 and P2179 is set at the same time, this indicates that both banks of the engine are operating lean. Inspect for items that would cause both banks of the engine to operate lean.
  3. 5:  Disconnecting the mass air flow (MAF) sensor determines if the MAF sensor signal is skewed. If the Short Term FT parameter changes more than the specified value, there is a condition with the MAF sensor. A MAF sensor condition can cause this DTC without setting a MAF DTC. If there is a MAF sensor condition, the MAF sensor parameters will appear to be within range.
  4. 6:  A vacuum leak causes DTC P2177 and P2179 to set at the same time. Inspect all areas of the engine for a vacuum leak. Also inspect the 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.
DTC P2177 or P2179

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 are set, except P2177 or P2179, refer to those DTCs before proceeding with this diagnostic.
  1. Idle the engine at the normal operating temperature.
  2. The fuel system is in Closed Loop.
  3. Observe the Total Fuel Trim Avg. parameter for bank 1 or bank 2 with a scan tool.
Is the Total Fuel Trim Avg. less than the specified value indicated?		 23% Go to Step 3  Go to Step 4 
3
  1. Observe the Freeze Frame and/or the Failure records data for this DTC.
  2. Turn the ignition OFF 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 and/or the Failure records data.
Does the DTC fail this ignition cycle?		 - Go to Step 4  Go to Diagnostic Aids
4  Are both banks of the engine operating lean? - Go to Step 5  Go to Step 7 
5 
  1. Start the engine.
    2. IMPORTANT: Additional DTCs set with the mass air flow (MAF) sensor disconnected.
  2. Disconnect the MAF sensor harness connector while the engine is operating.
  3. Observe the Short Term FT parameter for bank 1 and bank 2 with a scan tool.
  4. Connect the MAF sensor after completing this step.
Does the Short Term FT parameter for both banks of the engine change more than the specified value with the MAF sensor disconnected?		 20% Go to DTC P0101 Go to Step 6 
6  Inspect for the following conditions:
Did you find and correct the condition?		 - Go to Step 8  Go to Fuel System Diagnosis
7 Inspect for the following conditions:
  • Inspect for vacuum leaks that only affect one bank of the engine. For example, the intake manifold, the injector O-rings.
  • Inspect for lean injectors. Refer to Fuel Injector Coil Test .
  • Inspect for exhaust leaks, missing or loose exhaust hardware. Refer to Symptoms - Engine Exhaust in Engine Exhaust.
  • 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 in Engine Mechanical - 3.6L (LY7).

Did you find and correct the condition?		 - Go to Step 8  Go to Diagnostic Aids
8
  1. Turn OFF the ignition for 30 seconds.
  2. Start the engine.
  3. Reset the fuel trim system with a scan tool.
  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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