How To Test The EVAP Vent Solenoid (1999-2002 V8 Chevrolet Silverado, GMC Sierra)

In this tutorial, I'll explain how to test the EVAP vent solenoid in a step-by-step way. All of the test steps are explained in detail.

You'll be able to easily find out if it's bad or not. Your test result will also help you find out if the EVAP vent solenoid itself is behind a trouble code P0446 or P0449.

You can find this tutorial in Spanish here: Cómo Probar El Solenoide De Ventilación EVAP (1999-2002 V8 Chevrolet Silverado, GMC Sierra) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

Chevrolet:

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

GMC:

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

Symptoms Of A Bad EVAP Vent Solenoid

The EVAP vent solenoid's job is to control the intake of fresh air into the EVAP carbon canister.

Most of the time, the EVAP vent solenoid, is in an OFF state. In this OFF state, the EVAP vent solenoid lets fresh air intake into the carbon canister.

When the fuel injection computer commands the EVAP vent solenoid ON, it closes and blocks fresh air intake into the EVAP carbon canister.

When the EVAP vent solenoid fails, it'll usually not be able to close and shut off fresh air intake when commanded ON by the fuel injection computer.

A bad EVAP vent solenoid usually doesn't cause any engine performance problems or drive-ability issues.

Generally you'll only see one or more of the following symptoms:

1. The check engine light will be illuminated by one of the following trouble codes:
   • P0446: Evaporative Control System Vent Valve Performance.
   • P0449: EVAP Canister Vent Solenoid Control Circuit Problem.
2. Pressure in the gas tank when you remove the gas tank cap.
3. Your Silverado (Sierra) fails the emissions test.
4. Difficulty filling up the gas tank with fuel.

You can find a more detailed explanation of the P0446 and P0449 EVAP vent solenoid trouble codes here:

• P0446 -What Does It Mean? (1999-2006 V8 Chevrolet Silverado, GMC Sierra).
• P0449 -What Does It Mean? (1999-2006 V8 Chevrolet Silverado, GMC Sierra).

Where To Buy The EVAP Vent Solenoid

The AC-Delco brand is the original equipment (O.E.) part for your Chevrolet Silverado (GMC Sierra). Dorman is another trusted brand.

The following links will help you comparison shop for the EVAP vent solenoid:

What Tools Do I Need?

To test the EVAP vent solenoid, you'll need:

• A multimeter.
• Two jumper wires with insulated alligator clips.

The insulated alligator clips will help you avoid shorting the jumper wires together when connecting them to the male spade terminal of the EVAP vent solenoid when bench-testing it.

You'll need hand tools to remove the EVAP vent solenoid from its place underneath your Chevrolet Silverado (GMC Sierra).

TEST 1: Making Sure That The EVAP Vent Solenoid Is Getting Power

The EVAP vent solenoid gets 12 Volts DC from the ENG 1 fuse located in the underhood fuse box.

The wire that delivers this voltage to the EVAP vent solenoid is the pink (PNK) wire of its 2-wire connector.

The first we'll do is to make sure that the vent solenoid is getting 10 to 12 Volts from the PNK wire.

In the photo above, the PNK wire connects to the female terminal labeled with the letter B.

OK, let's start:

1. 1

   Disconnect the EVAP vent solenoid from its connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the black multimeter test lead to a good Ground point on the frame.
   
   NOTE: It's important that you Ground the black multimeter test lead to a clean and uncorroded spot on your Silverado or Sierra's frame to get a correct test result. What I personally do is use a battery jump start cable to connect the black multimeter test lead to the battery negative (-) terminal to ensure a good connection to Ground.

4. 4

   With the red multimeter test lead, gently probe the terminal labeled with the letter B.
   
   Terminal B is the one that connects to the PNK wire.

5. 5

   Have your helper turn the key to the RUN position but don't crank or start the engine.

6. 6

   The multimeter should register 10 to 12 Volts.

Let's take a look at what your test results mean:

CASE 1: 10 to 12 Volts DC are present. This is the correct and expected test result.

The next step is to go to: TEST 2: Making Sure The EVAP Solenoid Is Allowing Fresh Air Intake.

CASE 2: The indicated voltage is not present. Without power, the EVAP vent solenoid will not function.

This is usually caused by one of two things:

• The ENG 1 fuse is blown in the underhood fuse box.
• There's an open-circuit problem in the wiring between the EVAP vent solenoid's connector and the underhood fuse box.

Your next step is to check the fuse and retest for the presence of 10 to 12 Volts in terminal B.