DTC P0446. Oldsmobile Alero 2002

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 2002 🢒 Alero 🢒 Engine 🢒 Engine Controls - 2.2L (L61) 🢒 DTC P0446

Circuit Description

A restricted or blocked evaporative emission (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, P0116, P0117, P0118, P0122, P0123, P0452, or P0453 are not set.

•	The ignition voltage is between 10-18 volts.

•	The barometric pressure (BARO) is more than 75 kPa.

•	The fuel level is between 15-85 percent.

•	The engine coolant temperature (ECT) is between 4-30°C (39-86°F).

•	The intake air temperature (IAT) is between 4-30°C (39-86°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/h (75 mph).

Conditions for Setting the DTC

•	The FTP is less than -10 inch H2O.

•	The condition is present for as long as 30 seconds.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. 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.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

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

This step checks if the FTP sensor is functioning.

This step checks if the condition is present.

This step checks the EVAP vent valve electrical operation.

This step checks for a restricted EVAP vent valve

This step checks if the restriction is in the EVAP canister or the vent hose.

Step

Action

Values

Yes

Schematic Reference: Evaporative Emissions Hose Routing Diagram and Engine Controls Schematics

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Does the scan tool indicate that DTCs P0452 or P0453 also set?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

Inspect the EVAP system for the following conditions:

•	A damaged EVAP canister vent valve

•	A pinched EVAP vent hose

Did you find and correct the condition?

Go to Step 19

Go to Step 4

Install the J 41415-40 Fuel Tank Cap Adapter to the fuel filler neck.
Install the J 41413 EVAP Pressure/Purge Diagnostic Station and the fuel tank cap to the J 41415-40 .
Turn ON the ignition, with the engine OFF.
Command the EVAP canister vent valve ON, closed with a scan tool.
With the J 41413 , pressurize the EVAP system to the specified value.
Rotate the J 41413 rotary switch to the OFF/HOLD position.
Using the scan tool, compare the FTP sensor value to the J 41413 gauge value.

Are the EVAP pressure/purge diagnostic station gage and the scan tool FTP sensor values similar?

13 in H2O

Go to Step 5

Go to Step 9

Monitor the J 41413 gage.
Command the EVAP canister vent valve OFF.

Did the EVAP pressure/purge diagnostic station gage drop quickly to near the specified value?

0 in H2O

Go to Intermittent Conditions

Go to Step 6

Command the EVAP canister vent valve ON and OFF with a scan tool.

Do you hear or feel the EVAP vent valve click when commanded ON and OFF?

Go to Step 7

Go to Step 10

Disconnect the EVAP vent hose from the EVAP canister vent valve.

Did the EVAP pressure/purge diagnostic station gage drop quickly to near the specified value?

0 in H2O

Go to Step 14

Go to Step 8

Disconnect the EVAP vent hose from the EVAP canister.

Did the EVAP pressure/purge diagnostic station gage drop quickly to near the specified value?

0 in H2O

Go to Step 16

Go to Step 15

Is the FTP sensor value more than the specified value?

4.3 V

Go to DTC P0453

Go to Step 12

Disconnect the EVAP canister vent valve harness connector. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .
Probe the EVAP canister vent valve control circuit with a test light connected to a B+. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test light illuminate?

Go to Step 11

Go to Step 14

Test the control circuit of the EVAP vent valve for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 13

Test for poor connections at the harness connector of the FTP. 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 19

Go to Step 17

Test for poor connections at the harness connector of the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.