For 1990-2009 cars

### Description

A restricted or blocked EVAP vent path is detected by the PCM 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 PCM 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, P0122, P0123, P0452, or P0453 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/h (75 mph).

### Conditions for Setting the DTC

• | Fuel tank pressure is less than -10 inches H2O.

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

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

### Conditions For Clearing the MIL/DTC

• | The powertrain control module (PCM) will turn OFF the MIL during the first trip in which the diagnostic has been run and passed.

• | The history DTC will clear when the PCM turns OFF the MIL.

• | The DTC can be cleared by using the 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. To repair a blockage in the EVAP system, refer to Evaporative Emission System Cleaning .

### Test Description

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

1. This step checks if the FTP sensor is functioning.

2. This step checks if the condition is present.

3. This step checks the EVAP vent valve electrical operation.

4. This step checks for a restricted EVAP vent valve.

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

#### DTC P0446

Step | Action | Values | 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 DTCs P0452 or P0453 also 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 19

Go to Step 4

4 |

1. Install the J 41415-40 Fuel Tank Cap Adaptor to the fuel filler neck.
2. Install the J 41413 EVAP Pressure/Purge Diagnostic Station and the fuel tank cap to the adaptor.
3. Turn ON the ignition, with the engine OFF.
4. Command the EVAP vent valve ON (closed) with a scan tool.
5. With the J 41413 , pressurize the EVAP system to the specified value.
6. Rotate the J 41413 rotary switch to the OFF/HOLD position.
7. Using the scan tool, compare the fuel tank pressure (FTP) sensor value to the EVAP Pressure/Purge Diagnostic Station gauge value.

Are the EVAP Pressure/Purge Diagnostic Station gauge and the scan tool FTP sensor values similar?

13 in H2O

Go to Step 5

Go to Step 9

5 |

1. Monitor the EVAP Pressure/Purge Diagnostic Station gauge.
2. Command the EVAP canister vent valve OFF (open).

Did the EVAP Pressure/Purge Diagnostic Station gauge drop quickly to near the specified value?

0 in H2O

Go to Intermittent Conditions

Go to Step 6

6 | Command the EVAP vent valve ON and OFF with a scan tool. Does the EVAP vent valve click when commanded ON and OFF? | -- | Go to Step 7 | Go to Step 10
7 |

1. Turn OFF the ignition.
2. Reconnect all previously disconnected hardware.
3. With a scan tool, command the EVAP vent valve ON.
4. With the J 41413 , pressurize the EVAP system to the first specified value.
5. Rotate the J 41413 rotary switch to the OFF/HOLD position.
6. Disconnect the EVAP vent hose from the EVAP vent valve.

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

13 in H2O

0 in H2O

Go to Step 14

Go to Step 8

8 | 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 16 | Go to Step 15
9 | Is the FTP sensor value more than the specified value? | 4.3 V | Go to DTC P0453 | Go to Step 12
10 |

1. Disconnect the EVAP vent valve harness connector.
2. Probe the EVAP vent valve control circuit with a test light connected to B+.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 14

11 | 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
12 | 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
13 | Test for poor connections at the harness connector of the PCM. 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 18
14 | Replace the EVAP vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
15 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
16 | Repair the blockage in the EVAP vent hose. Did you complete the repair? | -- | Go to Step 19 | --
17 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
18 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
19 |

1. Reconnect all of the EVAP hardware that was previously disconnected.
2. Turn ON the ignition, with the engine OFF.
3. Command the EVAP canister vent valve ON (closed) with a scan tool.
4. With the J 41413 , pressurize the EVAP system to the first specified value.
5. Rotate the J 41413 rotary switch to the OFF/HOLD position.
6. Command the EVAP canister vent valve OFF (open).

Is the EVAP Pressure/Purge Diagnostic Station valve near the second specified value?

13 in H2O

0 in H2O

Go to Step 20

Go to Step 3

20 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK