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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 P0449 >> Test Description
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Test Description

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

  1. 2:  Listen or feel for a click when the EVAP vent solenoid valve operates. Ensure that both the ON and the OFF states are commanded.
  2. 5:  This step verifies that the control module is providing ground to the EVAP vent solenoid valve.
  3. 6:  This step tests if the EVAP vent solenoid valve control circuit is grounded.
DTC P0449

Step Action Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Controls Connector End Views  or  Powertrain Control Module (PCM) Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Command the EVAP vent solenoid valve ON and OFF with the scan tool.
Do you hear or feel a click from the EVAP vent solenoid valve when commanded ON and OFF?		 Go to Step 3  Go to Step 4 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  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 4  Go to Intermittent Conditions
4
  1. Turn OFF the ignition.
  2. Disconnect the EVAP vent solenoid.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition 1 voltage circuit of the EVAP vent solenoid valve with a test lamp that is connected to a good ground. Refer toProbing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?		 Go to Step 5  Go to Step 11 
5 
  1. Connect a test lamp between the control circuit of the EVAP vent solenoid valve and the ignition 1 voltage circuit of the EVAP vent solenoid valve.
  2. Command the EVAP vent solenoid valve ON and OFF with a scan tool.
Does the test lamp turn ON or OFF with each command?		 Go to Step 9  Go to Step 6 
6  Does the test lamp remain illuminated with each command? Go to Step 8  Go to Step 7 
7 Test the control circuit for an open or short to voltage. Refer toCircuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 10 
8 Test the control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 10 
9 Test for an intermittent and for a poor connection at the EVAP vent solenoid valve. Refer toTesting for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 12 
10 Test for an intermittent and for a poor connection at the control module. Refer toTesting for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 13 
11 Repair the open or short to ground in the ignition 1 voltage circuit. Refer toCircuit Testing and Wiring Repairs in Wiring Systems. Replace the fuse if necessary.
Did you complete the repair?		 Go to Step 14  -
12 Replace the EVAP vent solenoid valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
Did you complete the replacement?		 Go to Step 14  -
13 Replace the control module. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 Go to Step 14  -
14
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition 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/Failure Records.
Did the DTC fail this ignition?		 Go to Step 2  Go to Step 15 
15 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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