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HOMESERVICE MANUALSCHEVROLET2006COBALT SS, 4D SEDAN, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 303 (ENGINE CONTROL SYSTEM - 3.6L (LY7) - DTC P0442 TO DTC P1551)DTC P0449TEST DESCRIPTION
2006 Chevrolet Cobalt SS, 4D Sedan, Standard

Test Description

2006 Chevrolet Cobalt SS, 4D Sedan, StandardSECTION Test Description
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  This step determines if the condition exists. An audible click should be heard when the EVAP canister vent valve is commanded ON and OFF. Repeat the commands as necessary.
  2. 4:  This step tests the battery positive voltage circuit to the EVAP canister vent valve.
  3. 5:  This step tests the control modules ability to supply a ground to the EVAP canister vent valve.
DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 
  1. Start the engine.
  2. Allow the engine to reach operating temperature.
  3. Observe the DTC Info with a scan tool.
Did the DTC fail this ignition?		 - Go to Step 4  Go to Step 3 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 4  Go to Diagnostic Aids 
4 
  1. Turn OFF the ignition.
  2. Disconnect the evaporative emission (EVAP) canister vent valve harness connector. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the EVAP canister vent valve with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 5  Go to Step 10 
5 
  1. Connect a test lamp between the control circuit of the EVAP canister vent valve and the battery positive voltage circuit of the EVAP canister vent valve.
    2. IMPORTANT: The DTCs may need to be cleared if the output control does not operate.
  2. Command the EVAP canister vent valve ON and OFF with a scan tool.
Does the test lamp turn ON and OFF?		 - Go to Step 7  Go to Step 6 
6 Test the control circuit of the EVAP canister vent valve for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 9 
7 Measure the voltage from the control circuit of the EVAP canister vent valve to the engine control module (ECM) housing with a DMM.
Is the voltage within the specified range?		 2.6-4.6 V Go to Step 8  Go to Step 12 
8 Test for an intermittent and for a poor connection at the EVAP canister vent valve. 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 11 
9 Test for an intermittent and for a poor connection at the 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 13  Go to Step 12 
10 Repair the battery positive voltage circuit of the EVAP canister vent valve for an open. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 13  -
11 Replace the EVAP canister vent valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
Did you complete the replacement?		 - Go to Step 13  -
12 Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 13  -
13
  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 14 
14
  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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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.