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Home >> Cadillac >> 2005 >> CTS Base, 2.8 T, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 2.8L (DTC P0420 To P1551) >> Engine Controls Diagnosis >> DTC P0446 >> Test Description

Test Description

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

  1. 3:  This step determines if a condition exists with the fuel tank pressure (FTP) sensor. The FTP sensor parameter should display near zero inches of H2O with the fuel fill cap removed and the EVAP purge hose disconnected from the EVAP purge solenoid. Higher ambient air temperatures, or vehicle under-body temperatures could cause a higher than normal FTP reading. Allow the vehicle and/or the air surrounding the fuel tank to cool before proceeding with this step.
  1. 4:  The EVAP vent solenoid valve is located inside the EVAP canister. The EVAP canister must be removed from the vehicle, to access the EVAP vent solenoid valve. Once the EVAP solenoid vent valve has been removed from the EVAP canister, the electrical connector is re-connected. The vent solenoid valve is observed while being commanded ON and OFF with a scan tool.
DTC P0446 Evaporative Emission (EVAP) Vent System Performance

Step Action Values Yes No
Schematic Reference:  Evaporative Emissions (EVAP) Hose Routing Diagram 
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 Inspect the evaporative emission (EVAP) system for the following conditions:
  • A damaged EVAP vent valve
  • A collapsed or restricted EVAP vent hose/pipe (if equipped)
  • A damaged EVAP canister

Did you find and correct the condition?		 - Go to Step 10  Go to Step 3 
3 
IMPORTANT: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure.
  1. Turn OFF the ignition.
  2. Disconnect the purge line from the EVAP canister purge solenoid.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the Fuel Tank Pressure sensor parameter with a scan tool.
Is the Fuel Tank Pressure sensor parameter within the specified range?		 -1 and +1 in H20 Go to Step 4  Go to Step 6 
4 
  1. Turn OFF the ignition.
  2. Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement .
  3. Remove the EVAP vent valve from the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
  4. With the EVAP canister removed from the vehicle, connect the EVAP vent valve electrical connector.
  5. Turn ON the ignition with the engine OFF.
    6. IMPORTANT: The DTCs may need to be cleared if the output control does not operate.
  6. Command the EVAP vent valve ON and OFF with a scan tool.
Does the EVAP vent valve open and close?		 - Go to Step 5  Go to Step 7 
5
  1. Remove the fresh air inlet cover from the EVAP canister.
  2. Inspect the fresh air inlet for a restriction or a blockage.
  3. Inspect the fresh air inlet filter for a restriction or a blockage.
Did you find and correct the condition?		 - Go to Step 10  Go to Step 8 
6 Test for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor and at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 10  Go to Step 9 
7 Replace the EVAP vent valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
Did you complete the replacement?		 - Go to Step 10  -
8 Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement .
Did you complete the replacement?		 - Go to Step 10  -
9 Replace the fuel tank pressure (FTP) sensor. Refer to Fuel Tank Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 10  -
10
IMPORTANT: Do not exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  1. Turn OFF the ignition.
  2. Connect all disconnected components.
  3. Connect the J 41413-200  Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source.Special Tools .
  4. Install the GE-41415-50  Fuel Tank Cap Adapter to the fuel fill pipe.
  5. Connect the J 41413-200  nitrogen/smoke supply hose to the .Special Tools .GE-41415-50  .
  6. Turn ON the ignition with the engine OFF.
    7. IMPORTANT: The DTCs may need to be cleared if the output control does not operate.
  7. Command the EVAP vent solenoid closed with a scan tool.
  8. Turn the nitrogen/smoke valve on the J 41413-200  control panel to NITROGEN.Special Tools .
  9. Use the remote switch to pressurize the EVAP system to the first specified value.
  10. Observe the Fuel Tank Pressure sensor parameter with a scan tool.
  11. Command the EVAP vent solenoid open with a scan tool.
Is the Fuel Tank Pressure sensor parameter less than the second parameter?		 5 in H2O
1 in H2O		 Go to Step 11  Go to Step 2 
11
  1. Clear the DTCs with a scan tool.
  2. 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 in Vehicle DTC Information System OK
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