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Diagnostic Aids

WARNING: This page is about a different car, the 2004 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
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 Inspect the EVAP system for the following conditions:
Did you find and correct the condition?		 - Go to Step 15  Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Disconnect the purge line from the EVAP canister purge solenoid valve. Refer to Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement (L36)Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement (L67) .
  3. Turn ON the ignition, with the engine OFF.
Is the Fuel Tank Pressure sensor parameter within the Specified range?		 -1 to +1 in H20 Go to Step 4  Go to Step 10 
4
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 canister 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 Fuel Tank Pressure sensor parameter with a scan tool.
  12. Command the EVAP canister vent solenoid valve open with a scan tool.
Is the Fuel Tank Pressure sensor parameter less than the second specified value?		 5 in H2O
1 in H2O		 Go to Step 5  Go to Step 7 
5
  1. Connect the nitrogen/smoke hose to the EVAP service port.
  2. Remove the J 41415-40  .
  3. Install the fuel fill cap to the fuel fill pipe.
  4. Start the engine.
  5. Allow the engine to idle.
  6. Use the purge/seal function to seal the system with a scan tool.
  7. Command the EVAP canister purge solenoid valve to 30 percent.
  8. Observe the vacuum/pressure gage on the J 41413-200  and the FTP parameter on the scan tool.
  9. Allow the vacuum to increase on the gage of the J 41413-200  until it reaches approximately 16 in H2O.
  10. Use the purge/seal function to seal the system with a scan tool.
Is the FTP parameter on a scan tool within the specified value of the vacuum/pressure gage on the J 41413-200  until the vacuum reached the abort limit on a scan tool?		 1 in H2O Go to Step 6  Go to Step 10 
6 Did the FTP parameter on a scan tool display more than the specified value? 3.2 V Go to Diagnostic Aids Go to Step 12 
7 Disconnect the EVAP vent hose from the EVAP canister vent solenoid valve.
Is the Fuel Tank Pressure sensor parameter less than the specified value?		 1 in H2O Go to Step 13  Go to Step 8 
8 Disconnect the EVAP vent hose from the EVAP canister.
Is the Fuel Tank Pressure sensor parameter less than the specified value?		 1 in H2O Go to Step 9  Go to Step 14 
9 Repair the pinched or restricted EVAP vent hose.
Did you complete the repair?		 - Go to Step 15  -
10 Test for an intermittent and for a poor connection at the FTP sensor. 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 15  Go to Step 11 
11 Test the low reference circuit of the FTP sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
12 Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 15  -
13 Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement .
Did you complete the replacement?		 - Go to Step 15  -
15 Perform the Service Bay Test. Refer to Service Bay Test .
Does the scan tool indicate that the Service Bay Test passed?		 - Go to Step 16  Go to Step 3 
16 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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