Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | The Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
DTC Descriptors
DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Valve Control CircuitDTC 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ignition Voltage | P0498 | P0449 | -- | -- |
EVAP Canister Vent Solenoid Valve Control Circuit | P0498 | P0449 | P0499 | -- |
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
| • | Before the ECM can report DTC P0449, P0498, or P0499 failed, DTC P0451 must run and pass. |
| • | The engine speed is more than 80 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 run continuously once the above conditions are met. |
Conditions for Setting the DTC
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 4 seconds or a cumulative of 50 seconds.
DTC 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 exists for 4 seconds or a cumulative of 50 seconds.
DTC P0499
The ECM detects the voltage on the EVAP canister vent valve control circuit is more than 4.6 volts when the driver is commanded ON. The condition exists for 4 seconds or a cumulative of 50 seconds.
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
Connector End View Reference
Description and Operation
Evaporative Emission Control System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
- Command the EVAP vent solenoid valve ON and OFF with the scan tool. An audible click should be heard when changing between the commanded states.
- Start the engine, observe the DTC information with a scan tool. DTCs P0449, P0498, or P0499 should not set.
- 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.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the EVAP vent solenoid valve.
- Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal A and ground.
- Ignition OFF, connect a test lamp between the control circuit terminal B and the ignition voltage circuit terminal A.
- Ignition ON, use a scan tool to command the EVAP vent solenoid valve ON and OFF. The test lamp should turn ON and OFF.
- Test for 2.6-4.6 volts between the control circuit terminal B and ground.
- If all circuits/connections test normal, test or replace the EVAP vent solenoid valve.
Important: The ignition circuit supplies voltage to other components. Make sure you test all circuits for a short to ground or test all components for being shorted that share the ignition circuit.
| ⇒ | 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. |
Important: The control circuit for the EVAP vent solenoid valve is pulled-up to voltage within the ECM, 2.6-4.6 volts on the control circuit is normal.
| ⇒ | If the test lamp remains ON all the time, test for a short to ground on the control circuit. If circuit/connections test normal, replace the ECM. |
| ⇒ | If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM. |
| ⇒ | If the voltage is not within the specified range, replace the ECM. |
Component Testing
- Measure for 20-24 ohms of resistance between the terminals of the EVAP vent solenoid valve.
- Test for infinite resistance between each terminal of the EVAP vent solenoid valve and the EVAP vent solenoid valve housing.
| ⇒ | If the resistance is not within the specified range, replace the EVAP vent solenoid valve . |
| ⇒ | If less than infinite resistance, replace the EVAP vent solenoid valve. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
