Circuit Description
A battery positive is supplied to the evaporative emission (EVAP) canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.
The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister vent solenoid valve.
Control Module Command | EVAP Canister Vent Solenoid Valve Position |
|---|---|
ON | CLOSED |
OFF | OPEN |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0449 Evaporative Emission (EVAP) vent Solenoid Control Circuit
Conditions for Running the DTC
| • | The engine speed is more than 400 RPM. |
| • | The system voltage is between 10-18 volts. |
| • | DTC P0449 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The control module detects that the commanded state of the driver and the actual state of the control circuit do not match. |
| • | The above conditions are present for a minimum of 5 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Listen for a click when the valve operates. Verify that both the ON and the OFF states are commanded.
-
This step verifies that the control module is providing ground to the EVAP canister vent solenoid valve.
-
This step tests if the EVAP canister vent solenoid valve control circuit is grounded.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Do you hear or feel a click from the EVAP canister vent solenoid valve when the valve is commanded ON and OFF? | Go to Step 3 | Go to Step 4 | |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections |
4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 11 |
Does the test lamp turn ON and OFF with each command? | Go to Step 9 | Go to Step 6 | |
Does the test lamp remain illuminated with each command? | Go to Step 8 | Go to Step 7 | |
7 | Test the control circuit of the EVAP canister vent solenoid valve for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 10 |
8 | Test the control circuit of the EVAP canister vent solenoid valve for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the EVAP canister vent solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
10 | Inspect for poor connections at the harness connector of the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
11 |
Important: If the fuse is open, inspect all related circuits for a short to ground. Repair the open or short to ground in the battery positive voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 14 | -- |
12 | Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | Go to Step 14 | -- |
13 | Replace the engine control module (ECM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 14 | -- |
14 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 15 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
