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 P0498: Evaporative Emission (EVAP) Vent Solenoid Valve Control Circuit Open
DTC P0499: Evaporative Emission (EVAP) Vent Solenoid Valve Control Circuit Shorted

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | P0498 | P0498 | -- | --
EVAP Canister Vent Solenoid Valve Control Circuit | P0498 | P0498 | P0499 | --

### Circuit/System Description

The evaporative emission (EVAP) vent solenoid valve is used for EVAP system diagnostics. The EVAP vent solenoid valve is a normally open valve. Ignition voltage is supplied directly to the EVAP vent solenoid 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 ignition is ON or the engine is operating.

• | The DTCs runs continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0498

The ECM detects the EVAP vent solenoid valve control circuit is open.

#### P0499

The ECM detects the EVAP vent solenoid valve control circuit is shorted to ground or voltage.

### Action Taken When the DTC Sets

• | DTC P0498 and P0499 are Type A DTCs.

• | The EVAP system will only purge during open loop.

### Conditions for Clearing the DTC

DTC P0498 and P0499 are Type A 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. Engine running, command the EVAP Vent Solenoid ON and OFF with a scan tool. You should feel or hear an audible click as the solenoid is commanded ON and OFF.
2. 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 harness connector at the EVAP vent solenoid valve.
2. Ignition ON, verify a test lamp illuminates between the ignition 1 voltage circuit terminal 2 and ground.

⇒ | If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

3. Ignition OFF, connect a test lamp between the control circuit terminal 1 and the ignition 1 voltage circuit terminal 2.
4. Ignition ON, command the EVAP vent solenoid valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.

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

5. If all circuits test normal, test or replace the EVAP vent solenoid valve.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the EVAP vent solenoid valve.
2. Test for 18-28 ohms of resistance between the control terminal 1 and the ignition 1 voltage terminal 2.

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

3. Test for infinite resistance between each terminal and the EVAP vent solenoid valve housing.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming