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

#### P0443

An ignition voltage is supplied directly to the evaporative emission (EVAP) canister purge solenoid valve. The EVAP canister purge solenoid valve is pulse width modulated (PWM). The scan tool displays the amount of ON time as a percentage. The control module monitors the status of the driver. The control module controls the EVAP canister purge solenoid valve ON time by grounding the control circuit via an internal switch called a driver.

#### P0449

Battery voltage is supplied to the EVAP canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver.

### 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 control module detects that the commanded state of the driver and the actual state of the control circuit do not match, for a minimum of 12 seconds.

### Action Taken When the DTC Sets

DTC P0443 and P0449 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P0443 and P0449 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Controls Connector End Views

• | Engine Control Module 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

• | Scan Tool Data Definitions

• | Scan Tool Data List

• | Scan Tool Output Controls

### Circuit/System Verification

#### P0443

With the 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.

#### P0449

1. With the ignition ON and the 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.

### Circuit/System Testing

#### P0443

1. Ignition OFF, disconnect the harness connector at the EVAP canister purge 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 volage 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 solenoid to 50 percent with a scan tool. The test lamp should flash or illuminate when commanded to 50 percent and turn OFF when commanded to 0 percent.

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

⇒ | 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 control module.

5. If all circuits test normal, replace the EVAP canister purge solenoid valve.

#### P0449

1. Ignition OFF, disconnect the harness connector at the EVAP canister vent solenoid valve.
2. Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.

⇒ | If a 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 vent solenoid valve.

3. Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.
4. Command the solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between commanded states.

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

⇒ | 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 control module.

5. If all circuits test normal, replace the EVAP canister vent 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 engine control module (ECM) replacement, setup, and programming