For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### DTC Descriptor

DTC P0446: Evaporative Emissions (EVAP) Vent System Performance

### Circuit/System 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.

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

Control Module Command | EVAP Canister Purge Valve | EVAP Canister Vent Valve
--- | --- | ---
ON | Open | Closed
OFF | Closed | Open

### Conditions for Running the DTC

• | Before the ECM can report DTC P0446 failed, DTCs P0451, P0452, and P0453 must run and pass.

• | DTCs P0100, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0125, P0128, P0221, P0222, P0223, P0443, P0449, P0451, P0452, P0453, P0458, P0459, P0496, P0498, P0499, P0560, P0562, P0563, P0722, P0723, P2122, P2123, P2127, P2128 and P2138 are not set.

• | The ignition voltage is more than 10.5 volts.

• | The fuel system is operating in Closed Loop.

• | The engine run time is more than 10 minutes or the fuel trim is stable.

• | The engine is idling.

• | The FTP is between -18.7 and +7.5 mm Hg (-10.0 and +4.0 in. H2O).

• | The ambient air temperature (AAT) is between -7 and 32°C (19-90°F).

• | The ECT and the AAT are within 10°C (18°F) of each other at engine start-up.

• | The fuel level is between 12-88 percent.

• | The vehicle speed sensor (VSS) is less than 2 km/h (3 mph).

• | The above conditions exist for more than 5 seconds.

• | DTC P0446 will attempt to run up to 10 times or until the test completes successfully once per ignition cycle.

### Conditions for Setting the DTC

• | The FTP is less than -6.0 mm Hg (-3.2 in. H2O).

• | The condition is present for more than 4 seconds or a cumulative of 50 seconds.

### Action Taken When the DTC Sets

DTC P0446 is a Type B DTC.

### Conditions for Clearing the 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 valve inlet or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.

### Reference Information

#### Schematic Reference

Evaporative Emissions Hose Routing Diagram

#### Description and Operation

Evaporative Emission Control System Description

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

#### Special Tools Required

• | J 41413-SPT High Intensity White Light

• | J 41413-VLV EVAP Port Vent Fitting Tool

• | J 41413-200 Evaporative Emissions System Tester (EEST)

• | J 41413-300 EVAP Cap and Plug Kit

• | CH-48096 EVAP Service Port Access Tool

• | GE-41415-50 Fuel Tank Cap Adapter

### Circuit/System Testing

1. Verify DTCs P0458, P0459, P0498, P0499, P0452, or P0453 are not set.

⇒ | If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Disconnect the purge line from the EVAP purge valve.
3. Ignition ON, observe the fuel tank pressure sensor parameter with a scan tool. The FTP sensor parameter should be 0 inches H2O. If the pressure is not at 0 inches H2O, verify the FTP sensor voltage is less than 4.7 volts.

⇒ | If the FTP sensor voltage is more than 4.7 volts, refer to DTC P0452 or P0453 .

4. Reconnect all previously disconnected EVAP hardware.

Important: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.

5. Remove the fuel fill cap and connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
6. Ignition ON, seal the EVAP system with a scan tool.
7. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen.

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

8. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 inches H20.
9. While observing the FTP sensor parameter with a scan tool, command the EVAP vent valve OFF. Verify the FTP Sensor parameter is 0 inches H2O.

⇒ | If not at the specified value, test for a blockage or a restriction in the EVAP vent hose, or replace the EVAP vent solenoid valve.

10. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Repair Instructions

• | Evaporative Emission Canister Vent Solenoid Valve Replacement

• | Evaporative Emission Canister Vent Hose Replacement

### Repair Verification

1. Ignition ON, seal the EVAP system with a scan tool.
2. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen.

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

3. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 inches H20.
4. While observing the FTP sensor parameter with a scan tool, command the EVAP vent valve OFF.
5. Verify the FTP Sensor parameter is 0 inches H2O.