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Home >> Buick >> 2004 >> Century Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls (DTC P0140 To P0496) >> Engine Controls Diagnosis >> DTC P0446 >> Test Description
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Test Description

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

  1. 4:  This test determines if the failure is present or intermittent.
DTC P0446

Step
 		 Action Values Yes No
Schematic Reference:  Evaporative Emissions (EVAP) Hose Routing Diagram 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Perform the Service Bay Test. Refer to Service Bay Test .
Does the scan tool indicate that the Service Bay Test passed?		 - Go to Diagnostic Aids Go to Step 3 
3 Inspect the EVAP system for the following conditions:
Did you find and correct the condition?		 - Go to Step 13  Go to Step 4 
4 
  1. Turn OFF the ignition.
  2. Disconnect the purge line from the EVAP purge solenoid valve. Refer to Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement .
  3. Turn ON the ignition, with the engine OFF.
Is the fuel tank pressure (FTP) sensor parameter within the specified range?		 -1 to + 1 in H20 Go to Step 5  Go to Step 9 
5
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. Reconnect the EVAP purge pipe.
  3. Connect the J 41413-200  Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source.
  4. Install the J 41415-40  Fuel Fill Cap Adapter to the fuel fill pipe.
  5. Connect the fuel fill cap to the J 41415-40  .
  6. Connect the J 41413-200  nitrogen/smoke supply hose to the J 41415-40  .
  7. Turn ON the ignition with the engine OFF.
  8. Command the EVAP vent solenoid valve CLOSED with a scan tool.
  9. Turn the nitrogen/smoke valve on the J 41413-200  control panel to NITROGEN.
  10. Use the remote switch to pressurize the EVAP system to the first specified value.
  11. Observe the FTP sensor parameter with a scan tool.
  12. Command the EVAP vent solenoid valve OPEN with a scan tool.
Is the FTP sensor parameter less than the second specified value?		 5 in H2O
1 in H2O		 Go to Diagnostic Aids Go to Step 6 
6 Disconnect the EVAP vent hose from the EVAP vent solenoid.
Is the FTP sensor parameter less than the specified value?		 1 in H2O Go to Step 11  Go to Step 7 
7 Disconnect the EVAP vent hose from the EVAP canister.
Is the FTP sensor parameter less than the specified value?		 1 in H2O Go to Step 8  Go to Step 12 
8 Repair the pinched or restricted EVAP vent hose.
Did you complete the repair?		 - Go to Step 13  -
9 Test for an intermittent and for a poor connection at the control module. 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 13  Go to Step 10 
10 Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 13  -
11 Replace the EVAP vent solenoid valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
Did you complete the replacement?		 - Go to Step 13  -
12 Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement .
Did you complete the replacement?		 - Go to Step 13  -
13 Perform the Service Bay Test. Refer to Service Bay Test .
Does the scan tool indicate that the Service Bay Test passed?		 - Go to Step 14  Go to Step 3 
14 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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