P0449 -What Does It Mean? (1999-2006 V8 Chevrolet Silverado, GMC Sierra)

A trouble code P0449: EVAP Canister Vent Solenoid Control Circuit Problem usually points to a bad EVAP vent solenoid that isn't closing when commanded ON by the fuel injection computer.

In this tutorial, I'll explain what this trouble code means. I'll also talk about some of the tests you can perform to find its cause.

RELATED CODES: P0446 -What Does It Mean? (1999-2006 V8 Chevrolet Silverado, GMC Sierra).

You can find this tutorial in Spanish here: Código P0449 ¿Qué Significa? (1999-2006 V8 Chevrolet Silverado, GMC Sierra) (at: autotecnico-online.com).

APPLIES TO: This tutorial, on the P0449 OBD II trouble code, applies to the following vehicles:

Chevrolet:

• 4.8L Chevrolet Silverado (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
• 5.3L Chevrolet Silverado (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
• 6.0L Chevrolet Silverado (2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006

GMC:

• 4.8L GMC Sierra (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
• 5.3L GMC Sierra (1500, 2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
• 6.0L GMC Sierra (2500): 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006

What Does Trouble Code P0449 Mean?

A trouble code P0449: EVAP Canister Vent Solenoid Control Circuit Problem means that the EVAP vent solenoid is not functioning properly.

The EVAP vent solenoid's job is to allow ambient air into the charcoal canister so that fuel vapors can be purged from the activated carbon in the EVAP canister.

The EVAP vent solenoid also relieves EVAP system pressure that could cause fuel vapors to escape into the ambient air when the fuel tank cap is removed.

Normally, the EVAP vent solenoid is in an OFF state. In this OFF state, it allows fresh air to enter the EVAP charcoal canister and the EVAP system.

When the fuel injection computer (PCM = Powertrain Control Module) commands the EVAP vent solenoid ON, the solenoid closes and fresh air intake is cut off.

When the EVAP vent solenoid is commanded ON, EVAP system pressure increases and through the fuel tank pressure sensor, the fuel injection computer knows it's functioning correctly.

If when the EVAP solenoid is commanded ON (so that the solenoid will close and shut off fresh air intake) and the EVAP system pressure does not increase, then the fuel injection computer sets a P0449 trouble code.

Common Symptoms Of A P0449 Trouble Code

Generally, a problem with the EVAP system does not cause any drive-ability issues. You probably won't notice any engine performance problems at all.

What you will experience will be:

• The check engine light will be illuminated in the instrument panel.
• Pressure in the gas tank when you remove the gas tank cap.
• Your Silverado (Sierra) fails the emissions test.
• Difficulty filling up the gas tank with fuel.

What Does The EVAP System Do?

The purpose of the evaporative emission control (EVAP) system is to capture the fuel tank vapors and prevent them from escaping into the ambient air (the atmosphere).

The EVAP system, on the 1999-2006 V8 Chevrolet Silverado (GMC Sierra), consists of following basic components:

• Gas cap.
• Fuel tank.
• EVAP vent solenoid.
• Fuel tank pressure sensor.
• Fuel pipes and hoses.
• Vapor lines.
• EVAP emission canister (charcoal canister).
• Purge lines.
• EVAP purge control solenoid.

NOTE: It's important that you consult your vehicle's emissions label and a repair manual to find out which components make up the EVAP system on your specific Chevy Silverado (GMC Sierra).

What Causes A P0449 Trouble Code?

In the majority of cases, a bad EVAP vent solenoid is the cause of the P0449 trouble code lighting up the check engine light on your Chevrolet Silverado (GMC Sierra).

Although a bad EVAP vent solenoid is the most common cause of a P0449 trouble code, in some cases it's not. The following EVAP system faults can also cause a P0449 trouble code:

• EVAP vent solenoid is not getting 12 Volts.
• EVAP vent solenoid control circuit has an open-circuit or a short-circuit problem between the solenoid's connector and the fuel injection computer's connector.
• EVAP vent solenoid's electrical connector is damaged.

How To Diagnose And Repair A P0449 Trouble Code

Troubleshooting and solving a trouble code P0449 involves locating the EVAP vent solenoid and testing it.

I recommend the following:

• Remove the vent solenoid and blow it out with compressed air.
• Remove the vent solenoid's air filter and blow it with compressed air.
• On the 1999-2002 Silverado (Sierra), check that the EVAP solenoid is getting 10 to 12 Volts from the pink (PNK) with the key in the RUN position (but with the engine off).
• On the 2003-2006 Silverado (Sierra), check that the EVAP solenoid is getting 10 to 12 Volts from the orange (ORG) with the key in the RUN position (but with the engine off).
• Bench test the EVAP vent solenoid by applying 12 Volts and Ground and seeing if it 'clicks'.

For the 1999-2002 V8 Silverado (Sierra), you can find the EVAP solenoid bench-test here: How To Test The EVAP Vent Solenoid (1999-2002 V8 Chevrolet Silverado, GMC Sierra).

If your EVAP vent solenoid's bench-test confirms that the solenoid DOES NOT click when you apply/remove 12 Volts and Ground, then you can conclude that the EVAP vent solenoid is bad and needs to be replaced.

More Chevrolet Silverado (GMC Sierra) Tutorials

You can find a complete list of V8 Chevrolet Silverado (GMC Sierra) tutorials in this index:

• GM 4.8L, 5.3L, 6.0L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• Resistance Specifications Of The TAC Electronic Throttle Body.
• How To Test The GM Accelerator Pedal Position (APP) Sensor 2.
• How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L).
• Blown Head Gasket Test (GM 4.8L, 5.3L, 6.0L).