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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1383 (Engine Control System Diagnosis (DTC P0130 To DTC P0456) -- 1.8L (LNK)) >> Diagnosis >> DTC P0446 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. 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. 3:  This step verifies that the DTC P0446 is captured in the freeze frame/failure record list. When multiple EVAP system DTCs are set, the DTC stored in the freeze frame/failure record is the best diagnostic starting point.
  2. 28:  This step uses the EVAP Purge/Seal function to test for the correct operation of the EVAP canister vent solenoid, the pressure switching solenoid, and the purge solenoid. Using the EVAP Purge/Seal function also tests for leaks by allowing the technician to seal the system and monitor the FTP sensor.
DTC P0446

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics and Evaporative Emissions (EVAP) Hose Routing Diagram
Connector End View Reference:  Powertrain Control Module (PCM) Connector End Views  or  Engine Controls 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 Install a scan tool and check for DTCs.
Is a DTC P0450. P0451, P0452, or P0453 present?		 - Go to Scan Tool Data List Go to Step 3 
3 
  1. Review the Freeze Frame/Failure Records
  2. Diagnose the DTC captured in the Freeze Frame/Failure records first.
Is DTC P0446 captured in the Freeze Frame/Failure records?		 - Go to Step 4  Go to Diagnostic Trouble Code (DTC) List
4 Command the EVAP vent solenoid ON and OFF with the scan tool. Refer to Scan Tool Output Controls .
Do you hear or feel a click as the EVAP vent solenoid is commanded ON and OFF?		 - Go to Step 5  Go to Step 11 
5 Command the EVAP pressure switching solenoid ON and OFF with the scan tool.
Do you hear or feel a click as the EVAP pressure switching solenoid is commanded ON and OFF?		 - Go to Step 6  Go to Step 13 
6
  1. Remove the fuel fill cap in order to release any pressure inside the fuel tank.
  2. Re install the fuel fill cap.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the FTP sensor parameter on the scan tool.
Is the FTP sensor within the specified range?		 0.17 mm Hg (0.09 in H2O) Go to Step 7  Go to Step 20 
7
  1. Disconnect the EVAP solenoid vent hose at the EVAP canister.
  2. Command the EVAP vent solenoid ON, closed
  3. Install a vacuum pump to the vent hose, and apply a vacuum.
Did you achieve a vacuum?		 - Go to Step 8  Go to Step 22 
8 Command the EVAP vent solenoid OFF, open.
Does the vacuum decrease?		 - Go to Step 9  Go to Step 23 
9
  1. Disconnect the EVAP pressure switching solenoid hose from one of the ports.
  2. Command the EVAP pressure switching solenoid OFF, closed
  3. Install a vacuum pump to the solenoid port and apply a vacuum.
Did you achieve a vacuum?		 - Go to Step 10  Go to Step 25 
10 Command the EVAP pressure switching ON, open.
Does the vacuum decrease?		 - Go to Step 28  Go to Step 25 
11
  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the EVAP vent solenoid.
  3. Connect a test lamp between the ignition positive voltage circuit of the EVAP vent solenoid and a known good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 12  Go to Step 17 
12
  1. Connect a test lamp between the ignition positive voltage circuit of the EVAP vent solenoid and the control circuit of the EVAP vent solenoid. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
  2. Command the EVAP vent solenoid ON, with a scan tool.
Does the test lamp illuminate when the EVAP vent solenoid is commanded ON and turn OFF when the EVAP vent solenoid is commanded OFF?		 - Go to Step 18  Go to Step 15 
13
  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the EVAP pressure switching solenoid.
  3. Connect a test lamp between the ignition positive voltage circuit of the EVAP pressure switching solenoid and a known good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 14  Go to Step 17 
14
  1. Connect a test lamp between the ignition positive voltage circuit of the EVAP pressure switching solenoid and the control circuit of the EVAP pressure switching solenoid. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
  2. Command the EVAP pressure switching solenoid ON, with a scan tool.
Does the test lamp illuminate when the EVAP pressure switching solenoid is commanded ON and turn OFF when the EVAP pressure switching solenoid is commanded OFF?		 - Go to Step 19  Go to Step 16 
15 Test the control circuit of the EVAP vent solenoid for an open, short to ground, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 21 
16 Test the control circuit of the EVAP pressure switching solenoid for an open, a short to ground, or for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 21 
17
  1. Repair the open or short to ground in the ignition positive voltage circuit of the EVAP solenoid. Refer to Wiring Repairs in Wiring Systems.
  2. Replace the fuse as necessary.
Did you complete the repair?		 - Go to Step 28  -
18 Test for an intermittent and for a poor connection at the EVAP canister vent solenoid. 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 28  Go to Step 24 
19 Test for an intermittent and for a poor connection at the EVAP pressure switching solenoid. 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 28  Go to Step 25 
20 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 28  Go to Step 26 
21 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 28  Go to Step 27 
22
  1. Inspect for a leak source in the EVAP solenoid vent hose.
  2. Repair as necessary
Did you find and correct the condition?		 - Go to Step 28  Go to Step 24 
23
  1. Inspect for a blockage or restriction in the EVAP solenoid vent hose.
  2. Repair as necessary
Did you find and correct the condition?		 - Go to Step 28  Go to Step 24 
24 Replace the EVAP vent solenoid. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .
Did you complete the replacement?		 - Go to Step 28  -
25 Replace the EVAP pressure switching solenoid. Refer to Evaporative Emission (EVAP) Pressure Switching Solenoid Replacement .
Did you complete the replacement?		 - Go to Step 28  -
26 Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement .
Is the action complete?		 - Go to Step 28  -
27 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Is the action complete?		 - Go to Step 28  -
28 
  1. Start the engine.
  2. Select the EVAP Purge Seal function on the scan tool.
  3. Command the EVAP Purge Seal function ON. Refer to Service Bay Test .
Does the FTP sensor indicate a reading of at least the first specified value for as long as the second specified value?		 -28.20 mm Hg (-15.10 in H2O)
2 minutes		 Go to Step 29  Go to Step 4 
29 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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