GM calls the EGR valve on the 1990-1994 3.1L V6 engine a digital EGR valve (yup, purty fancy name if you ask me).
This 'digital' EGR valve is made up of three individual solenoids that control the opening/closing of three ports on the base of the EGR valve.
Although the EGR valve looks like a complicated component to test, nothing could be further from the truth.
In this tutorial, I'll explain how to test it step by step without expensive diagnostic equipment. Your test results will quickly determine if the digital EGR valve is good or bad.
Contents of this tutorial:
- Important Testing Tips.
- Symptoms Of A Bad EGR Valve.
- EGR Valve Circuit Descriptions.
- Tools Needed To Test The EGR Valve.
- TEST 1: Making Sure The EGR Valve Is Getting 12 Volts.
- TEST 2: Testing The Resistance Of The Solenoids.
- TEST 3: EGR Solenoid A Performance Test.
- TEST 4: EGR Solenoid B Performance Test.
- TEST 5: EGR Solenoid C Performance Test.
- More 3.1L Chevrolet And Pontiac Diagnostic Tutorials.
You can find this tutorial in Spanish here: Cómo Probar La Válvula EGR (1990-1994 3.1L V6 Chevrolet y Pontiac) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.1L Chevrolet Beretta: 1990, 1991, 1992, 1993.
- 3.1L Chevrolet Cavalier: 1990, 1991, 1992, 1993, 1994.
- 3.1L Chevrolet Celebrity: 1990.
- 3.1L Chevrolet Corsica: 1990, 1991, 1992, 1993.
- 3.1L Chevrolet Lumina: 1990, 1991, 1992, 1993, 1994.
- 3.1L Pontiac 6000: 1990, 1991.
- 3.1L Pontiac Grand Prix: 1990, 1991, 1992, 1993.
- 3.1L Pontiac Sunbird: 1991, 1992, 1993, 1994.
Important Testing Tips
Although testing the EGR valve isn't a complicated process, the following precautions will help you avoid some common headaches/complications:
TIP 1: You'll need to remove the EGR valve from the vehicle to test it using the instructions in this tutorial.
It's important to remove the EGR valve with a cold engine. If the engine has been running for any length of time, allow it to cool completely.
The EGR valve can get very hot if the engine has been running for any length of time.
TIP 2: You'll need to use jumper wires with insulated alligator clips to bench-test the EGR valve using this tutorial's instructions. The insulated alligator clip jumper wires will help you avoid short-circuit complications.
TIP 3: You'll need a 9 Volt alkaline battery to test the EGR valve solenoids. Although you can use the vehicle's battery, it's easier and safer to use a 9 Volt battery.
Symptoms Of A Bad EGR Valve
The symptoms your vehicle will experience depend on the type of EGR system failure.
To be more specific, an EGR system failure generally causes an engine performance problem but not always.
In some instances, an EGR failure will light up the check engine light and set an EGR system failure diagnostic trouble code in the computer's memory and nothing more (go figure).
The diagnostic trouble code you'll see is:
- Code 32: EGR System Error.
You may also see one or more of the following symptoms:
- Rough idle.
- Really bad gas mileage.
- Lack of power as you accelerate the vehicle down the road.
- Vehicle seems to run OK above 30 miles and hour but once you come to an idle, the engine barely stays running.
- Vehicle runs great, just the annoying check engine light is on with diagnostic trouble code 32 stored in the fuel injection computer's memory.
EGR Valve Circuit Descriptions
The EGR valve connector has five wires sticking out of it. To successfully diagnose the EGR valve, we need to know what each one does.
The following table has a brief description of each:
|A||Light Blue (LT BLU)||Solenoid A Control|
|B||Brown With White Stripe (BRN/WHT) or Brown (BRN)||Solenoid B Control|
|C||Red (RED)||Solenoid C Control|
|D||Brown (BRN)||12 Volts|
IMPORTANT: More than likely, the color of the wires will not be the same on your vehicle. Don't worry. The terminal circuit description will be the same regardless of the color of the wire it connects to.
Tools Needed To Test The EGR Valve
You won't need expensive diagnostic equipment to test the EGR valve, just a few basic things.
Here's a list of the basic tools you'll need to use the information in this tutorial
- Jumper wires with insulated alligator clips on the ends.
- A 9 Volt alkaline battery.
- A multimeter.
You can buy the insulated alligator clip jumper wires at your local auto parts store or you can buy them online here:
TEST 1: Making Sure The EGR Valve Is Getting 12 Volts
To get this show on the road, I'll ask you first to ensure the EGR valve is getting power.
This power is in the form of 10 to 12 Volts DC and is provided by the terminal labeled with the letter D (see the photo above).
These 12 Volts feed all three solenoids within the EGR valve, and if it's missing, none will work.
Let's get testing:
Disconnect the EGR valve from its connector.
Place your multimeter in Volts DC mode.
Connect the black multimeter test lead to the battery negative (-) terminal.
Turn the key to the ON position but don't crank or start the engine.
With the red multimeter test lead, gently probe the female terminal labeled with the letter D.
Your multimeter should read 10 to 12 Volts DC.
Let's interpret your test result:
CASE 1: The multimeter registered 10 to 12 Volts. This is the correct and expected test result.
Now that you've confirmed that the EGR valve is getting power, the next step is to check the internal resistance of each solenoid. For this test, go to: TEST 2: Testing The Resistance Of The Solenoids.
CASE 2: The multimeter did not register 10 to 12 Volts. Without power, the EGR valve will not function.
Your next step is to find out why this voltage is missing and resolve the issue. Once power is restored, repeat this test.