How To Test The EVRV Solenoid (1988-1993 2.8L Chevrolet S10, GMC S15 Pickup, GMC Sonoma)

The EGR vacuum solenoid isn't difficult to test and in this tutorial, I'll show you how in a step by step manner.

With your test results, you'll quickly determine if the EVRV solenoid is good or bad.

NOTE: The EGR valve vacuum solenoid is called the Electronic Vacuum Regulator Valve (EVRV) solenoid in the GM service literature.

APPLIES TO: This tutorial applies to the following vehicles:

• 2.8L Chevrolet S10 Pickup: 1988, 1989, 1990, 1991, 1992, 1993.
• 2.8L GMC S15 Pickup: 1988, 1989, 1990.
• 2.8L GMC Sonoma: 1991, 1992, 1993.

EGR VALVE TEST: You can find the EGR valve test here:

• How To Test The EGR Valve (1988-1995 4.3L TBI Chevrolet S10, GMC Sonoma).

Symptoms Of A Bad EVRV Solenoid

When the EVRV solenoid fails, you may or may not see an engine performance issue other than a trouble code 32 and the check engine light illuminated.

Why? This is due to the fact that the EVRV solenoid fails in one of two ways:

• The EVRV solenoid is stuck closed and does not supply vacuum to the EGR valve when the computer commands it ON.
• The EVRV solenoid is stuck open and allows vacuum to flow to the EGR valve at all times.

If the EVRV solenoid is stuck open, you'll see one or more of the following engine performance issues:

• Check engine light is illuminated and the following diagnostic trouble code is registered in the fuel injection computer's memory:
  • Code 32: EGR System Problem.
• Engine is hard to start.
• Engine shuts off when decelerating.
• Engine starts but idles rough.
• Engine starts but won't stay running.

If the EVRV solenoid is stuck closed, you'll see one or more of the following issues:

• Check engine light is illuminated and the following diagnostic trouble code is registered in the fuel injection computer's memory:
  • Code 32: EGR System Problem.
• Engine knock (engine pinging).

How The EVRV Solenoid Works

In a nutshell, the EVRV solenoid is tasked with supplying or cutting off vacuum to the EGR valve when the fuel injection computer commands it ON or OFF.

Here are more specifics on how the EVRV solenoid works:

• The EVRV solenoid receives 12 Volts DC as soon as the engine is started, but remains OFF (does not allow vacuum to flow thru it).
• Once the engine has reached normal operating temperature and is under load, the fuel injection computer commands the EVRV solenoid ON.
• The fuel injection computer commands the EVRV solenoid ON by grounding it internally.
  • The EVRV solenoid is a PWM (Pulse Width Modulation) type solenoid.
  • In plain English, this means that the EVRV solenoid's ON time is controlled by the fuel injection computer, which cycles it on and off many times per second.
• The fuel injection computer varies the ON time to vary the amount of vacuum the solenoid sends the EGR valve.
• When the EGR valve receives vacuum, it opens and allows exhaust gas to enter the intake manifold.

It's important to note that the EVRV solenoid is normally closed. In other words, it does not allow vacuum to flow from its inlet port to its outlet port (until it's commanded ON).

EVRV Solenoid Connector Circuit Descriptions

Here's a brief circuit description of the 3 wires coming out of its electrical connector:

Wire	Color	Description
A	Pink With Black Stripe (PNK/BLK)	12 Volts (Fuse)
B	Grey (GRY)	EVRV Solenoid Control
C	Empty	Not Used
D	Black With White Stripe (BLK/WHT)	Chassis Ground

What Tools Do I Need To Test The EVRV Solenoid

The two tools that make testing the EVRV solenoid valve a breeze are a handheld vacuum pump and a multimeter.

If you don't have a vacuum pump, you can borrow one from your local auto parts store (for a small deposit, which is refunded when you return the tool - AutoZone, O'Reilly Auto Parts).

If you'd like to a buy vacuum pump, this is my recommendation: Actron CP7835 Vacuum Pump (at: amazon.com).

You can find my multimeter recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.

TEST 1: Making Sure The EVRV Solenoid Is Getting Vacuum

IMPORTANT: Before testing the EVRV solenoid valve, you should first test the EGR valve and confirm it's working properly. You can find the EGR valve test here: How To Test The EGR Valve (1988-1995 4.3L TBI Chevrolet S10, GMC Sonoma).

The EVRV solenoid is connected to manifold vacuum. Once the engine starts, this manifold vacuum is continuously supplied to the EVRV solenoid.

The vacuum port labeled with the number 2 in the photo above is the port that receives continuous manifold vacuum when the engine is started.

To start our EVRV solenoid diagnostic, let's see if a continuous vacuum is supplied to the solenoid with the engine running.

CAUTION: This test is performed with the engine running. Be careful and take all necessary safety precaution!

Let's get started:

1. 1

   Disconnect the vacuum line labeled with the number 2 from the EVRV solenoid (see image above).

2. 2

   Start the engine and let it idle.

3. 3

   Check the vacuum line for vacuum.

4. 4

   The vacuum line should have vacuum.

Let's examine your test result:

CASE 1: Vacuum is present in the vacuum line. This is the correct and expected test result.

The next test is to make sure the EVRV solenoid is receiving 12 Volts. Go to: TEST 2: Making Sure The EVRV Solenoid Is Getting 12 Volts.

CASE 2: Vacuum IS NOT present in the vacuum line. Without vacuum, the EVRV solenoid will not open the EGR valve when given its ON signal from the fuel injection computer.

Your next step is to ensure that the EVRV solenoid inlet vacuum port is connected to the correct vacuum port on the throttle body.

Once vacuum is restored to the EVRV solenoid (with the engine idling), clear the EGR system trouble code and road test your vehicle to see if the EGR system problem is resolved.