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 P0443: Evaporative Emission (EVAP) Purge Solenoid Control Circuit
DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Ignition 1 Voltage - Purge Supply | P0443 | P0443 | P0443 | -- | --
Battery Positive - Vent Supply | P0449 | P0449 | P0449 | -- | --
EVAP Purge Solenoid Control | P0443 | P0443 | P0443 | P0443 | --
EVAP Vent Solenoid Control | P0449 | P0449 | P0449 | P0449 | --

### Circuit/System Description

An ignition voltage is supplied directly to the evaporative emission (EVAP) canister purge solenoid valve. The engine control module (ECM) grounds the EVAP canister purge solenoid valve control circuit through an internal switch called a driver. The ECM monitors the status of the driver. The EVAP canister purge solenoid valve is pulse width modulated (PWM). A scan tool will display the amount of ON time as a percentage.

Battery voltage is supplied to the EVAP canister solenoid valve. The ECM grounds the EVAP canister vent solenoid valve control circuit through an internal switch called a driver. The ECM monitors the status of the driver. A scan tool will display the commanded state of the EVAP canister vent solenoid valve as ON or OFF.

### Conditions for Running the DTC

• | The ignition is ON.

• | The system voltage is between 9-18 volts.

• | DTCs P0443 and P0449 run continuously when 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 a minimum of 5 seconds.

### Action Taken When the DTC Sets

DTCs P0443 and P0449 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0443 and P0449 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Description and Operation

Evaporative Emission Control System Description

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Troubleshooting with a Test Lamp

• | 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

#### P0443

1. Ignition ON, engine OFF, you should hear a clicking sound when the EVAP canister purge solenoid valve is commanded to 50 percent with a scan tool. The clicking sound should stop when the EVAP canister purge solenoid valve is commanded to 0 percent. The rate at which the valve cycles should increase when the commanded state is increased, and decrease when the commanded state is decreased.
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.

#### P0449

1. Ignition ON, engine OFF, command the EVAP vent solenoid ON and OFF with a scan tool.
2. Listen for a click when the valve operates. Verify that both the ON, and the OFF states are commanded.
3. Operate the vehicle within the Conditions for Running the DTC. 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 canister purge or vent solenoid valve.
2. Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.

⇒ | If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the voltage supply circuit fuse is open, test or replace the EVAP canister purge solenoid.

3. Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.
4. Command the EVAP canister purge solenoid valve to 50 percent with a scan tool, or the EVAP canister vent solenoid valve ON and OFF. The test lamp should respond to the command.

⇒ | 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, 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, replace the appropriate solenoid valve.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Evaporative Emission Canister Purge Solenoid Valve Replacement

• | Evaporative Emission Canister Vent Solenoid Valve Replacement

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