GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 DTC P0446

Description

A restricted or blocked EVAP vent path is detected by the control module commanding the purge valve ON (open) and the vent valve ON (closed) allowing a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the purge valve OFF (closed) and the vent valve OFF (open) while monitoring the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, DTC P0446 will set.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1107, P1112, P1114, P1115, P1120, P1220 or P1221 are not set.
    • The ignition voltage is between 10 and 18 volts.
    • The barometric pressure is more than 75 kPa.
    • The fuel level is between 15 and 85 percent.
    • The engine coolant temperature (ECT) is between 4°C and 30°C (39°F and 86°F).
    • The intake air temperature (IAT) is between 4°C and 30°C (39°F and 86°F).
    • The start up ECT and IAT are within 9°C (16°F) of each other.
    • The vehicle speed sensor (VSS) is less than 121 km/hr (75mph).

Conditions for Setting the DTC
    •  The fuel tank pressure is less than -10 in. H2O.
    •  The condition is present for 30 seconds.

Action Taken When the DTC Sets
    • The control module will illuminate the malfunction indicator lamp (MIL) when the diagnostic test runs and fails.
    • The control module will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC
    • The control module will turn the malfunction indicator lamp (MIL) OFF during the first trip in which the diagnostic has been run and passed.
    • A last test failed (current DTC) clears when the control module turns OFF the MIL.
    • The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.

Test Description

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

  1. This test determines if the failure is present or intermittent.

DTC P0446

Step

Action

Value(s)

Yes

No

Schematic Reference: Emission 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

Did DTC P0443, P0449, P0452 or P0453 set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

Inspect the EVAP system for the following conditions:

    • A damaged EVAP vent valve
    • A pinched EVAP vent hose

Did you find and correct the condition?

--

Go to Step 14

Go to Step 4

4

  1. With a scan tool, review and record the Freeze Frame/Failure Records Data.
  2. With a scan tool, clear the DTC codes.
  3. Perform the Service Bay Test. Refer to.

Does the scan tool indicate that the Service Bay Test has passed?

--

Go to Diagnostic Aids

Go to Step 5

5
  1. Disconnect the purge line from the EVAP purge Valve.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the fuel tank pressure parameter.

Does the scan tool indicate fuel tank pressure near the specified value?

0 in H2O

Go to Step 6

Go to Step 8

6
  1. Turn OFF the ignition.
  2. Install the fuel fill cap adaptor.
  3. Connect the J 41413 EVAP pressure/purge diagnostic station and the J 41415-40 vehicle fuel fill cap to the fuel fill cap adaptor.
  4. Reconnect all previously disconnected hardware.
  5. Turn ON the ignition, with the engine OFF.
  6. With a scan tool, seal the EVAP system.
  7. With the J 41413 EVAP pressure/purge diagnostic station, pressurize the EVAP system to the first specified value.
  8. Turn the J 41413 EVAP pressure/purge diagnostic station rotary valve to the OFF/HOLD position.
  9. Disconnect the EVAP vent hose from the EVAP vent valve.

Does the scan tool indicate fuel tank pressure near the second specified value?

5 in H2O

0 in H2O

Go to Step 10

Go to Step 7

7

Disconnect the EVAP vent hose from the EVAP canister.

Does the scan tool indicate fuel tank pressure near the specified value?

0 in H2O

Go to Step 13

Go to Step 11

8

With a scan tool, observe the fuel tank pressure sensor voltage.

Is the FTP sensor voltage more than the specified value?

4.3 volts

Go to DTC P0453

Go to Step 9

9

Test for poor connections at the harness connector of the fuel tank pressure 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 14

Go to Step 12

10

Replace the EVAP vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .

Did you complete the replacement?

--

Go to Step 14

--

11

Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement .

Did you complete the replacement?

--

Go to Step 14

--

12

Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 14

--

13

Repair for a blockage in the EVAP vent hose.

Did you complete the repair?

--

Go to Step 14

--

14
  1. Reconnect all of the EVAP hardware that was previously disconnected.
  2. Perform the Service Bay Test. Refer to Service Bay Test .

Does the scan tool indicate that the Service Bay Test has passed?

--

Go to Step 15

Go to Step 3

15

With a scan tool, select the Review Info option

Does the scan tool indicate any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK