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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1387 (Engine Control System Diagnosis (DTC P0130 To DTC P0456) -- 1.8L (LV6)) >> Diagnosis >> DTC P0456 >> 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 P0456 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 preferred diagnostic starting point.
  2. 5:  The fuel filler pipe has two vent lines that allow for recirculation of fuel vapors between the fuel filler pipe and the fuel tank. Because of these vent lines the EEST can be connected to the EVAP service port for leak detection. Waiting until smoke is seen before plugging the EVAP canister drain hose speeds up the filling of the canister with smoke. Introducing smoke in between 60 second intervals of Nitrogen will speed up the filling of smoke in the fuel tank and filler pipe vapor space. This occurs because the pressure at which Nitrogen gas is applied is greater than the pressure at which smoke is introduced. The Nitrogen gas pushes the smoke that was just introduced through the canister and into the fuel tank. The EVAP vent solenoid DOES NOT have to be turned ON in order to test for leaks. A one way check valve located in the vent port of the EVAP canister provides containment of smoke and pressure within the EVAP system.
  3. 7:  This test verifies that the fuel tank pressure (FTP) sensor is accurate. An FTP sensor that does not correctly respond to vacuum, or pressure may cause this DTC to set.
DTC P0456

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. Install a scan tool.
  2. Check for DTCs.
Is a DTC P0450, P0451, P0452, or P0453 present?		 - Go to Diagnostic Trouble Code (DTC) 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 P0456 captured in the Freeze Frame/Failure records?		 - Go to Step 4  Go to Diagnostic Trouble Code (DTC) List
4
  1. Inspect the EVAP system for the following conditions:
    • A loose, missing, or damaged service port schrader valve
    • A loose, incorrect, missing, or damaged fuel fill cap
    • A damaged EVAP purge solenoid
  2. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Inspect the EVAP system for the following conditions:
    • Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses
    • A damaged EVAP vent solenoid or EVAP canister
Did you find and correct the condition?		 - Go to Step 10  Go to Step 5 
5 
IMPORTANT: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.
  1. Connect the nitrogen/smoke supply hose of theJ 41413-200  Evaporative Emission System Tester (EEST) to the EVAP service port.
  2. Turn the nitrogen/smoke valve on the control panel to SMOKE.
  3. Use the remote switch to introduce smoke into the EVAP system.
  4. Continue to introduce smoke until a steady flow of smoke is seen exiting the EVAP canister drain hose. Refer to Evaporative Emissions (EVAP) Hose Routing Diagram
  5. Plug the drain hose of the EVAP canister using the J 41413-301  plug. Refer to Evaporative Emissions (EVAP) Hose Routing Diagram .
  6. Turn the nitrogen/smoke valve on the control panel to NITROGEN.
  7. Use the remote switch to introduce Nitrogen gas into the EVAP system for 60 seconds.
  8. Inspect the entire EVAP system for exiting smoke with theJ 41413-SPT  .
  9. Continue to introduce smoke, then Nitrogen, at 60 second intervals, until the source of the leak has been located.
Did you locate and repair a leak source?		 - Go to Step 10  Go to Step 6 
6
  1. Remove the fuel fill cap
  2. Observe the FTP in H20 with the scan tool.
Is the FTP in H20 near the specified value?		 0.17 mm Hg (0.09 in H2O) Go to Step 7  Go to Step 9 
7 
  1. Install the fuel fill cap on the fuel fill pipe.
  2. Turn the nitrogen/smoke valve on theJ 41413-200  control panel to NITROGEN.
  3. Use the J 41413-200  to pressurize the EVAP system to the first specified value.
Is the FTP parameter more than the second specified value?		 18.68 mm Hg (10 in H2O)
9.34 mm Hg (5 in H2O)		 Go to Step 8  Go to Step 9 
8
  1. Use the remote switch to stop introducing nitrogen into the EVAP system.
  2. Disconnect the purge hose at the EVAP canister purge solenoid.
  3. Command the EVAP pressure switching solenoid ON.
Is the FTP Sensor parameter less than the specified value?		 1.86 mm Hg (1 in H2O) Go to Diagnostic Aids Go to Step 9 
9 Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement (FWD) or Fuel Tank Pressure Sensor Replacement (AWD) .
Did you complete the replacement?		 - Go to Step 10  -
10
IMPORTANT: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.
  1. Connect the nitrogen/smoke supply hose of theJ 41413-200  Evaporative Emission System Tester (EEST) to the EVAP service port.
  2. Plug the drain hose of the EVAP canister using the J 41413-301  plug. Refer to Evaporative Emissions (EVAP) Hose Routing Diagram .
  3. Turn the nitrogen/smoke valve to NITROGEN.
  4. Pressurize the EVAP system to the specified value.
  5. Observe the J 41413-200  pressure/vacuum gage for 5 minutes.
Does the pressure/vacuum gage remain constant?		 9.34 mm Hg (5 in H2O) Go to Step 11  Go to Step 5 
11 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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