P0449
DTC P0449, P0498, or P0499
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0449
- Evaporative Emission (EVAP) Vent Solenoid Control Circuit
DTC P0498
- Evaporative Emission (EVAP) Vent Solenoid Valve Control Circuit Low Voltage
DTC P0499
- Evaporative Emission (EVAP) Vent Solenoid Valve Control Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The evaporative emission (EVAP) canister vent valve is used for EVAP system diagnostics. The EVAP canister vent valve is a normally open valve. Battery positive voltage is supplied directly to the EVAP canister vent valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.
Conditions for Running the DTC
* The engine speed is greater than 0 RPM.
* The ignition voltage is between 10-18 volts.
* The ECM has commanded the EVAP canister vent valve ON and OFF at least once during the ignition cycle.
* The DTCs runs continuously once the above conditions are met.
Conditions for Setting the DTC
P0449
The ECM detects the voltage on the EVAP canister vent valve control circuit is between 2.6-4.6 volts when the driver is commanded OFF. The condition exists for less than 1 second.
P0498
The ECM detects the voltage on the EVAP canister vent valve control circuit is less than 2.6 volts when the driver is commanded OFF. The condition is present for greater than 1 second.
P0499
The ECM detects the voltage on the EVAP canister vent valve control circuit is greater than 4.6 volts when the driver is commanded ON. The condition is present for greater than 1 second.
Action Taken When the DTC Sets
* DTC P0449, P0498 and P0499 are Type B DTCs.
* The EVAP system will only purge during open loop.
Conditions for Clearing the DTC
DTC P0449, P0498 and P0499 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Evaporative Emission Control System Description (Evaporative Emission Control System Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Engine idling, command the EVAP vent solenoid ON and OFF with a scan tool while observing the following control circuit status parameters:
* EVAP Vent Sol Short Gnd Test Status
* EVAP Vent Sol Open Test Status
* EVAP Vent Sol Short Volts Test Status
Each parameter should display OK or Not Run.
2. Ignition ON, command the EVAP Vent Solenoid ON and OFF with a scan tool. The EVAP Vent Solenoid should respond to the scan tool commands.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, open the hood to disable the Auto-Stop function.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to DTC P254F (P254F).
3. Ignition OFF, disconnect the harness connector at the EVAP vent solenoid valve.
4. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal B and ground.
• If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition voltage circuit fuse is open, test all components connected to the ignition voltage circuit and replace as necessary.
5. Test for 3-4 V between the control circuit terminal A and ground.
• If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the ECM.
• If greater than the specified range, test the control circuit for a short to voltage. If circuit test normal, replace the ECM.
6. Command the EVAP vent solenoid valve ON and OFF with a scan tool. The DMM should transition from 3-4 V when ON to less than 0.1 V when commanded OFF.
• If the circuit voltage does not correspond to the specified values, replace the ECM.
7. If all circuits test normal, test or replace the EVAP vent solenoid valve.
Component Testing
1. Test for 18-24 ohm between the terminals of the EVAP vent solenoid valve.
• If not within the specified range, replace the EVAP vent solenoid valve.
2. Measure the resistance between each terminal of the EVAP vent solenoid valve and the EVAP vent solenoid valve housing. The DMM should display OL.
• If less than the specified value, replace the EVAP vent solenoid valve.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Evaporative Emission Canister Purge Solenoid Valve Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming