How To Test The EGR Valve (1996-1998 2.2L Chevrolet S10, GMC Sonoma)

How To Test The EGR Valve (1998, 1999, 2000 2.2L Chevrolet S10, GMC Sonoma, And Isuzu Hombre)

If the check engine light is illuminated by an EGR system fault trouble code, this tutorial will help you troubleshoot the problem.

This tutorial is a straightforward guide to testing the EGR valve on the 1996-1998 2.2L Chevrolet S10 pickup and GMC Sonoma pickup.

You'll quickly determine if the EGR valve is good or bad with step-by-step testing instructions.

In Spanish You can find this tutorial in Spanish here: Cómo Probar La Válvula EGR (1998-2000 2.2L Chevrolet S10, GMC Sonoma) (at:

APPLIES TO: This tutorial applies to the following vehicles:

  • 2.2L Chevrolet S10 Pickup: 1996, 1997, 1998.
  • 2.2L GMC Sonoma: 1996, 1997, 1998.
  • 2.2L Isuzu Hombre: 1998, 1999, 2000.

Symptoms Of A Bad EGR Valve

There's a good chance that your vehicle will not experience any engine performance issues when the EGR valve malfunctions.

In these cases, all you'll notice is the check engine light shining nice and bright on the instrument panel and nothing else (and an EGR system diagnostic trouble code stored in the computer's memory).

In the worst case scenarios, the EGR valve malfunction will cause engine performance issues.

Here's a basic list of symptoms you'll see when the EGR valve malfunctions:

  • Check engine light illuminated by one of the following diagnostic trouble codes:
    • P0401 EGR System Flow Insufficient.
    • P1406 EGR Valve Pintle Position.
  • 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 one of the above diagnostic trouble codes stored in the PCM's memory.
  • Engine starts and immediately dies.

EGR Valve Connector Circuits

The electronic EGR valve on your 1998-2000 2.2L Chevrolet S10 pickup (GMC Sonoma) has a 5-wire electrical connector.

To successfully diagnose the EGR valve as good or bad, we need to know what each circuit and wire does.

In the following table, you'll find a brief description of the EGR valve circuits:

Wire Color Description
A Grey (GRY) Chassis Ground
B Black (BLK) Sensor Ground
C Brown (BRN) EGR Pintle Position Signal
D Grey (GRY) 5 Volts
E Pink (PNK) EGR Valve Control

Where To Buy The EGR Valve And Save

If your test results confirm the EGR valve is bad or you just want to replace it right off the bat, the following links will help you comparison shop for the EGR valve of known automotive brands (avoid knock off parts).

Not sure if the above linear EGR valve fits your particular vehicle? Don't worry. Once you get to the site they'll make sure it fits by asking you the specifics of your particular vehicle. If it doesn't fit, they'll find you the right one.

TEST 1: EGR Pintle Position Signal Test

EGR Pintle Position Signal Test. How To Test The EGR Valve (1998, 1999, 2000 2.2L Chevrolet S10, GMC Sonoma, And Isuzu Hombre)

The EGR valve on your Chevrolet S10 (GMC Sonoma) has an internal pintle position sensor that measures how much the valve's pintle opens/closes.

In this first test section, we're going to check its output voltage and see if it's reporting that the EGR valve's pintle is stuck open.

The value we want to see is a voltage value between 0.6 to 0.9 Volts DC, which would indicate the EGR valve's pintle is in its closed position.

IMPORTANT: To perform this test, the EGR valve must remain connected to its pigtail connector. To access the signal within the wire, you'll need to back probe the connector or use a wiring piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe.

These are the test steps:

  1. 1

    Place your multimeter in Volts DC mode.

  2. 2

    Connect the red multimeter test lead to the brown (BRN) wire.

    The BRN wire connects to the terminal with the letter C.

    NOTE: The EGR valve must remain connected to its pigtail connector to read the pintle position voltage signal.

  3. 3

    Connect the black multimeter test lead to battery negative (-) terminal.

  4. 4

    Turn the key to the ON position but don't crank or start the engine.

  5. 5

    Your multimeter should display a voltage reading between 0.6 to 0.9 Volts DC.

Let's interpret your test results:

CASE 1: The multimeter registered 0.6 to 0.9 Volts DC. This is the correct and expected test result and it tells you that the EGR valve pintle is in the correct position (not stuck open).

Your next step is to go to: TEST 2: EGR Pintle Position Sensor Performance Test.

CASE 2: The multimeter displayed a DC voltage above 0.9 Volts. This test result usually indicates the pintle is stuck open.

To investigate this further, go to: TEST 7: Checking For Carbon Build Up.

CASE 3: The multimeter DID NOT display any voltage or a very low voltage. This test result usually indicates that the EGR valve is bad.

To investigate this further, your next step is check the EGR valve pintle position sensor's performance. For this test go to: TEST 2: EGR Pintle Position Sensor Performance Test.

Chevrolet Vehicles:

  • S10 Pickup 2.2L
    • 1998, 1999, 2000

GMC Vehicles:

  • Sonoma 2.2L
    • 1998, 1999, 2000

Isuzu Vehicles:

  • Hombre 2.2L
    • 1998, 1999, 2000