Buick Regal: DTC P0446

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0446

Evaporative Emission (EVAP) Vent System Performance

Typical Scan Tool Data

Circuit/System Description

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path.

There are two parts to this test.

• Part one uses the fuel tank pressure sensor to indicate vacuum comes within a calibrated value.
• The second part of this test looks for excessive vacuum which would indicate a restriction. The duration of this second part of is a function of purge volume through the system.

The table listed below illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP purge and vent solenoid valves.

Conditions for Running the DTC

• DTCs P00C8, P00C9, P00CA, P0068, P0090, P0091, P0092, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P012B, P012C, P012D, P017B, P017C, P017D, P0222, P0223, P0443, P0449, P0452, P0453, P0454, P0458, P0459, P0498, P0499, P0502, P0503, P0606, P0722, P0723, P0191, P0192, P0193, P06A3, P06DB, P06DE, P0A1D, P0601, P0604, P0697, P111E, P160D, P160E, P1682, P16A0, P16A1, P16A2, P16F3, P1104, P117B, P117C, P117D, P117E, P117F, P127A, P127C, P127D, P15F2, P1221, P2100, P2101, P2102, P2103, P2122, P2123, P2127, P2128, P2135, P2138, P215B, P2176, P2227, P2228, P2229, P2230, P228C, P228D, U0073, U0074, U0293, U1817 are not set.
• The ignition voltage is between 11 - 32 V.
• The barometric pressure (BARO) is greater than 70 kPa.
• The fuel level is between 10 - 90%.
• The startup engine coolant temperature (ECT) is less than 35ºC (95ºF).
• The startup intake air temperature (IAT) is between 4 - 34ºC (39 - 95ºF).
• DTC P0446 runs once per cold start.

Conditions for Setting the DTC

NOTE: There are two stages to setting this DTC. Stage one, prep test, then stage two test.

• If fuel tank pressure sensor reading is greater than 0.62 kPa (2.5 in H2O) of pressure or less than 1.24 kPa (5 in H2O) of vacuum for 60 s.

  OR

• If fuel tank pressure sensor reading is less than 2.98 kPa (12 in H2O) of vacuum for 5 s before 10 L (2.6 gal) of purge volume has passed through the system.
• After setting the DTC for the first time, 2 L (0.5 gal) of fuel must be consumed before setting the DTC for the second time.

Action Taken When the DTC Sets

DTC P0446 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0446 is a Type B DTC.

Diagnostic Aids

An intermittent condition could be caused by:

• A damaged EVAP vent housing
• A temporary blockage at the EVAP vent solenoid valve inlet
• Pinched vent hose

A blockage in the vent system may also cause a poor fuel fill problem.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Powertrain Component View

Powertrain Component Views

Description and Operation

Evaporative Emission Control System Description

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

• CH 41415-30 Fuel Tank Cap Adapter
• GE 41413-A Evaporative Emissions System Tester (EEST)

For equivalent regional tools, refer to Special Tools (Diagnostic Tools) and Special Tools (Mechanical Tools).

Circuit/System Verification

1. Ignition ON.

2. Verify DTC P0443 is not set.

• If the DTC is set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• Go to next step: If the DTC is not set

3. Ignition OFF, remove the fuel tank filler cap. Ignition ON.

4. Verify the scan tool Fuel Tank Pressure Sensor parameter is between 1.3 - 1.7 V.

• If not between the 1.3 - 1.7 V

Refer to P0452, P0453 within DTC P0451-P0454.

• Go to next step: If between the 1.3 - 1.7 V

5. Install the fuel tank filler cap. Engine idling at operating temperature for 5 min.

6. Verify the scan tool Fuel Tank Pressure Sensor parameter does not increase to greater than 2.5 V when commanding the EVAP Purge Solenoid Valve to 50%.

• If greater than 2.5 V

Refer to Circuit/System Testing.

• Go to next step: If 2.5 V or less

7. 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 data.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

8. All OK.

Circuit/System Testing

NOTE: Perform the Circuit/System Verification before proceeding with the Circuit/System Testing.

1. Test for a blockage or restrictions in the EVAP system components listed below and repair as necessary.

• Evaporative Emission Vent System Hoses
• Evaporative Emission Canister
• Q13 Evaporative Emission Vent Solenoid Valve
• Evaporative Emission Vent Filter

2. Reconnect all previously disconnected EVAP hardware.

NOTE: Refer to the GE 41413-A detailed instructions in Evaporative Emission System Diagnosis.

3. Remove the fuel fill cap and connect the CH 41415-30 to the fuel tank filler neck. Connect the GE 41413-A to the CH 41415-30.

4. Command the EVAP Purge/Seal function to System Seal with a scan tool to seal the EVAP system.

5. Turn the nitrogen/smoke valve on the GE 41413-A to nitrogen.

NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

6. Use the remote switch to activate the GE 41413-A and pressurize the fuel tank to 1.24 kPa (5.0 in H2O).

7. Verify the scan tool Fuel Tank Pressure Sensor parameter is 0 kPa (0 in H2O) when commanding the EVAP Vent Solenoid Valve to OFF.

• If not 0 in H20

Test for a blockage or a restriction in the EVAP vent hose or inlet. If the inlet or hose test normal, replace the Q13 Evaporative Emission Vent Solenoid Valve.

• Go to next step: If 0 in H2O

8. 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 data.

• If the DTC sets

Refer to step 1 above.

• Go to next step: If the DTC does not set

9. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Evaporative Emission Canister Solenoid Replacement (FWD) or Evaporative Emission Canister Solenoid Replacement (AWD) for EVAP Vent Solenoid Valve replacement
• Evaporative Emission Canister Replacement (AWD) or Evaporative Emission Canister Replacement (FWD)
• Fuel Tank Pressure Sensor Replacement (FWD) or Fuel Tank Pressure Sensor Replacement (AWD)

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