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 Descriptor

DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit

### 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. Battery 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.

• | The ignition voltage is between 11-18 volts.

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

### Conditions for Setting the DTC

The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 5 seconds.

### Action Taken When the DTC Sets

DTC P0449 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P0449 is a Type B DTC.

### 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. Ignition ON, command the EVAP Vent Solenoid ON and OFF with a scan tool. You should hear the solenoid click when commanded ON and OFF.
2. 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.

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, disconnect the harness connector at the EVAP vent solenoid.
2. Ignition ON, verify a test lamp illuminates between the B+ voltage circuit terminal B and ground.

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

3. Test for 2.5-3.5 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 the circuit/connections test normal, replace the ECM.

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Command the EVAP vent solenoid ON and OFF with a scan tool. The DMM should transition from 2.5-3.5 V when OFF to less than 0.1 V when commanded ON.

⇒ | If the circuit voltage does not correspond to the specified values, replace the ECM.

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

### Component Testing

1. Ignition OFF, disconnect the harness connector of the EVAP vent solenoid.
2. Test for 15-25 Ω between the control terminal A and the B+ voltage terminal B.

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

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

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Evaporative Emission Canister Vent Solenoid Valve Replacement

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