For 1990-2009 cars

### 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.

• | Diagnostic Procedure Instructions 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition Voltage | P0499 | P0498 | -- | --
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. If the ECM detects the control circuit voltage is within a predetermined range when the circuit is commanded OFF, this DTC sets.

### Conditions for Running the DTC

• | The engine speed is greater 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 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 4 seconds or for a cumulative time of 30 seconds.

#### 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 4 seconds or for a cumulative time of 30 seconds.

#### 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 4 seconds or for a cumulative time of 30 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

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Evaporative Emission Control System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. 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.
2. Start the engine, observe the scan tool EVAP Vent Solenoid Valve Circuit Test Status parameters. The circuit test status parameters should display OK or Not Run.
3. Engine Idling, observe the DTC information with a scan tool. DTC P0449, P0498, or P0499 should not set.
4. 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, disconnect the multi-way harness connector X305.
2. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal N 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.

3. Ignition OFF, connect a test lamp between the control circuit terminal M and the ignition voltage circuit terminal N.

Note: The control circuit for the EVAP vent solenoid valve is pulled-up to voltage within the ECM, 2.6-4.6 V on the control circuit is normal.

4. Ignition ON, command the scan tool EVAP vent solenoid valve function ON and OFF. The test lamp should turn ON and OFF.

⇒ | If the test lamp remains ON all the time, test the control circuit for a short to ground. If circuit/connections test normal, replace the ECM.

⇒ | If the test lamp remains OFF all the time, test the control circuit for a short to voltage or an open/high resistance. If circuit/connections test normal, replace the ECM.

5. Test for 2.6-4.6 V between the control circuit terminal M and ground.

⇒ | If not within the specified range, replace the ECM.

6. Remove the fuel tank. Refer to Fuel Tank Replacement.
7. Disconnect the EVAP vent solenoid valve harness connector.
8. Inspect the EVAP vent solenoid valve circuits in the fuel tank harness, between the EVAP vent solenoid valve connector and X305 for the following conditions, and repair as necessary:

• | Damaged wiring or terminals

• | Open circuits

• | Short to ground

• | Wire to wire short

9. If all circuits/connections test normal, test or replace the EVAP vent solenoid valve.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the EVAP vent solenoid.
2. Test for 20-24 Ω between the terminals of the EVAP vent solenoid.

⇒ | If not within the specified range, replace the EVAP vent solenoid valve.

3. 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 after completing the diagnostic procedure.

• | Evaporative Emission Canister Vent Solenoid Valve Replacement

• | Control Module References for ECM replacement, setup, and programming